Merge pull request #609 from aspnet/release/2.2

Introduce RoutePattern (#585)

src/Microsoft.AspNetCore.Routing/Patterns/RouteParameterParser.cs

@@ -0,0 +1,248 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    internal static class RouteParameterParser
+    {
+        // This code parses the inside of the route parameter 
+        //
+        // Ex: {hello} - this method is responsible for parsing 'hello'
+        // The factoring between this class and RoutePatternParser is due to legacy.
+        public static RoutePatternParameterPart ParseRouteParameter(string parameter)
+        {
+            if (parameter == null)
+            {
+                throw new ArgumentNullException(nameof(parameter));
+            }
+
+            if (parameter.Length == 0)
+            {
+                return new RoutePatternParameterPart(string.Empty, null, RoutePatternParameterKind.Standard, Array.Empty<RoutePatternConstraintReference>());
+            }
+
+            var startIndex = 0;
+            var endIndex = parameter.Length - 1;
+
+            var parameterKind = RoutePatternParameterKind.Standard;
+            if (parameter[0] == '*')
+            {
+                parameterKind = RoutePatternParameterKind.CatchAll;
+                startIndex++;
+            }
+
+            if (parameter[endIndex] == '?')
+            {
+                parameterKind = RoutePatternParameterKind.Optional;
+                endIndex--;
+            }
+
+            var currentIndex = startIndex;
+
+            // Parse parameter name
+            var parameterName = string.Empty;
+
+            while (currentIndex <= endIndex)
+            {
+                var currentChar = parameter[currentIndex];
+
+                if ((currentChar == ':' || currentChar == '=') && startIndex != currentIndex)
+                {
+                    // Parameter names are allowed to start with delimiters used to denote constraints or default values.
+                    // i.e. "=foo" or ":bar" would be treated as parameter names rather than default value or constraint
+                    // specifications.
+                    parameterName = parameter.Substring(startIndex, currentIndex - startIndex);
+
+                    // Roll the index back and move to the constraint parsing stage.
+                    currentIndex--;
+                    break;
+                }
+                else if (currentIndex == endIndex)
+                {
+                    parameterName = parameter.Substring(startIndex, currentIndex - startIndex + 1);
+                }
+
+                currentIndex++;
+            }
+
+            var parseResults = ParseConstraints(parameter, parameterName, currentIndex, endIndex);
+            currentIndex = parseResults.CurrentIndex;
+
+            string defaultValue = null;
+            if (currentIndex <= endIndex &&
+                parameter[currentIndex] == '=')
+            {
+                defaultValue = parameter.Substring(currentIndex + 1, endIndex - currentIndex);
+            }
+
+            return new RoutePatternParameterPart(parameterName, defaultValue, parameterKind, parseResults.Constraints.ToArray());
+        }
+
+        private static ConstraintParseResults ParseConstraints(
+            string text,
+            string parameterName,
+            int currentIndex,
+            int endIndex)
+        {
+            var constraints = new List<RoutePatternConstraintReference>();
+            var state = ParseState.Start;
+            var startIndex = currentIndex;
+            do
+            {
+                var currentChar = currentIndex > endIndex ? null : (char?)text[currentIndex];
+                switch (state)
+                {
+                    case ParseState.Start:
+                        switch (currentChar)
+                        {
+                            case null:
+                                state = ParseState.End;
+                                break;
+                            case ':':
+                                state = ParseState.ParsingName;
+                                startIndex = currentIndex + 1;
+                                break;
+                            case '(':
+                                state = ParseState.InsideParenthesis;
+                                break;
+                            case '=':
+                                state = ParseState.End;
+                                currentIndex--;
+                                break;
+                        }
+                        break;
+                    case ParseState.InsideParenthesis:
+                        switch (currentChar)
+                        {
+                            case null:
+                                state = ParseState.End;
+                                var constraintText = text.Substring(startIndex, currentIndex - startIndex);
+                                constraints.Add(RoutePatternFactory.Constraint(parameterName, constraintText));
+                                break;
+                            case ')':
+                                // Only consume a ')' token if
+                                // (a) it is the last token
+                                // (b) the next character is the start of the new constraint ':'
+                                // (c) the next character is the start of the default value.
+
+                                var nextChar = currentIndex + 1 > endIndex ? null : (char?)text[currentIndex + 1];
+                                switch (nextChar)
+                                {
+                                    case null:
+                                        state = ParseState.End;
+                                        constraintText = text.Substring(startIndex, currentIndex - startIndex + 1);
+                                        constraints.Add(RoutePatternFactory.Constraint(parameterName, constraintText));
+                                        break;
+                                    case ':':
+                                        state = ParseState.Start;
+                                        constraintText = text.Substring(startIndex, currentIndex - startIndex + 1);
+                                        constraints.Add(RoutePatternFactory.Constraint(parameterName, constraintText));
+                                        startIndex = currentIndex + 1;
+                                        break;
+                                    case '=':
+                                        state = ParseState.End;
+                                        constraintText = text.Substring(startIndex, currentIndex - startIndex + 1);
+                                        constraints.Add(RoutePatternFactory.Constraint(parameterName, constraintText));
+                                        break;
+                                }
+                                break;
+                            case ':':
+                            case '=':
+                                // In the original implementation, the Regex would've backtracked if it encountered an
+                                // unbalanced opening bracket followed by (not necessarily immediatiely) a delimiter.
+                                // Simply verifying that the parantheses will eventually be closed should suffice to
+                                // determine if the terminator needs to be consumed as part of the current constraint
+                                // specification.
+                                var indexOfClosingParantheses = text.IndexOf(')', currentIndex + 1);
+                                if (indexOfClosingParantheses == -1)
+                                {
+                                    constraintText = text.Substring(startIndex, currentIndex - startIndex);
+                                    constraints.Add(RoutePatternFactory.Constraint(parameterName, constraintText));
+
+                                    if (currentChar == ':')
+                                    {
+                                        state = ParseState.ParsingName;
+                                        startIndex = currentIndex + 1;
+                                    }
+                                    else
+                                    {
+                                        state = ParseState.End;
+                                        currentIndex--;
+                                    }
+                                }
+                                else
+                                {
+                                    currentIndex = indexOfClosingParantheses;
+                                }
+
+                                break;
+                        }
+                        break;
+                    case ParseState.ParsingName:
+                        switch (currentChar)
+                        {
+                            case null:
+                                state = ParseState.End;
+                                var constraintText = text.Substring(startIndex, currentIndex - startIndex);
+                                if (constraintText.Length > 0)
+                                {
+                                    constraints.Add(RoutePatternFactory.Constraint(parameterName, constraintText));
+                                }
+                                break;
+                            case ':':
+                                constraintText = text.Substring(startIndex, currentIndex - startIndex);
+                                if (constraintText.Length > 0)
+                                {
+                                    constraints.Add(RoutePatternFactory.Constraint(parameterName, constraintText));
+                                }
+                                startIndex = currentIndex + 1;
+                                break;
+                            case '(':
+                                state = ParseState.InsideParenthesis;
+                                break;
+                            case '=':
+                                state = ParseState.End;
+                                constraintText = text.Substring(startIndex, currentIndex - startIndex);
+                                if (constraintText.Length > 0)
+                                {
+                                    constraints.Add(RoutePatternFactory.Constraint(parameterName, constraintText));
+                                }
+                                currentIndex--;
+                                break;
+                        }
+                        break;
+                }
+
+                currentIndex++;
+
+            } while (state != ParseState.End);
+
+            return new ConstraintParseResults(currentIndex, constraints);
+        }
+
+        private enum ParseState
+        {
+            Start,
+            ParsingName,
+            InsideParenthesis,
+            End
+        }
+
+        private readonly struct ConstraintParseResults
+        {
+            public readonly int CurrentIndex;
+
+            public readonly IReadOnlyList<RoutePatternConstraintReference> Constraints;
+            
+            public ConstraintParseResults(int currentIndex, IReadOnlyList<RoutePatternConstraintReference> constraints)
+            {
+                CurrentIndex = currentIndex;
+                Constraints = constraints;
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePattern.cs

@@ -0,0 +1,74 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    [DebuggerDisplay("{DebuggerToString()}")]
+    public sealed class RoutePattern
+    {
+        private const string SeparatorString = "/";
+
+        internal RoutePattern(
+            string rawText,
+            Dictionary<string, object> defaults,
+            Dictionary<string, IReadOnlyList<RoutePatternConstraintReference>> constraints,
+            RoutePatternParameterPart[] parameters,
+            RoutePatternPathSegment[] pathSegments)
+        {
+            Debug.Assert(defaults != null);
+            Debug.Assert(constraints != null);
+            Debug.Assert(parameters != null);
+            Debug.Assert(pathSegments != null);
+
+            RawText = rawText;
+            Defaults = defaults;
+            Constraints = constraints;
+            Parameters = parameters;
+            PathSegments = pathSegments;
+        }
+
+        public IReadOnlyDictionary<string, object> Defaults { get; }
+
+        public IReadOnlyDictionary<string, IReadOnlyList<RoutePatternConstraintReference>> Constraints { get; }
+
+        public string RawText { get; }
+
+        public IReadOnlyList<RoutePatternParameterPart> Parameters { get; }
+
+        public IReadOnlyList<RoutePatternPathSegment> PathSegments { get; }
+
+        /// <summary>
+        /// Gets the parameter matching the given name.
+        /// </summary>
+        /// <param name="name">The name of the parameter to match.</param>
+        /// <returns>The matching parameter or <c>null</c> if no parameter matches the given name.</returns>
+        public RoutePatternParameterPart GetParameter(string name)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            for (var i = 0; i < Parameters.Count; i++)
+            {
+                var parameter = Parameters[i];
+                if (string.Equals(parameter.Name, name, StringComparison.OrdinalIgnoreCase))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private string DebuggerToString()
+        {
+            return RawText ?? string.Join(SeparatorString, PathSegments.Select(s => s.DebuggerToString()));
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternConstraintReference.cs

@@ -0,0 +1,46 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Diagnostics;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    /// <summary>
+    /// The parsed representation of a constraint in a <see cref="RoutePattern"/> parameter.
+    /// </summary>
+    [DebuggerDisplay("{DebuggerToString()}")]
+    public sealed class RoutePatternConstraintReference
+    {
+        internal RoutePatternConstraintReference(string parameterName, string content)
+        {
+            ParameterName = parameterName;
+            Content = content;
+        }
+
+        internal RoutePatternConstraintReference(string parameterName, IRouteConstraint constraint)
+        {
+            ParameterName = parameterName;
+            Constraint = constraint;
+        }
+
+        /// <summary>
+        /// Gets the constraint text.
+        /// </summary>
+        public string Content { get; }
+
+        /// <summary>
+        /// Gets a pre-existing <see cref="IRouteConstraint"/> that was used to construct this reference.
+        /// </summary>
+        public IRouteConstraint Constraint { get; }
+
+        /// <summary>
+        /// Gets the parameter name associated with the constraint.
+        /// </summary>
+        public string ParameterName { get; }
+
+        private string DebuggerToString()
+        {
+            return Content;
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternException.cs

@@ -0,0 +1,42 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Runtime.Serialization;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    [Serializable]
+    public sealed class RoutePatternException : Exception
+    {
+        private RoutePatternException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            Pattern = (string)info.GetValue(nameof(Pattern), typeof(string));
+        }
+
+        public RoutePatternException(string pattern, string message)
+            : base(message)
+        {
+            if (pattern == null)
+            {
+                throw new ArgumentNullException(nameof(pattern));
+            }
+
+            if (message == null)
+            {
+                throw new ArgumentNullException(nameof(message));
+            }
+
+            Pattern = pattern;
+        }
+
+        public string Pattern { get; }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            info.AddValue(nameof(Pattern), Pattern);
+            base.GetObjectData(info, context);
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternFactory.cs

@@ -0,0 +1,504 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNetCore.Routing.Constraints;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    public static class RoutePatternFactory
+    {
+        public static RoutePattern Parse(string pattern)
+        {
+            if (pattern == null)
+            {
+                throw new ArgumentNullException(nameof(pattern));
+            }
+
+            return RoutePatternParser.Parse(pattern);
+        }
+
+        public static RoutePattern Parse(string pattern, object defaults, object constraints)
+        {
+            if (pattern == null)
+            {
+                throw new ArgumentNullException(nameof(pattern));
+            }
+
+            var original = RoutePatternParser.Parse(pattern);
+            return Pattern(original.RawText, defaults, constraints, original.PathSegments);
+        }
+
+        public static RoutePattern Pattern(IEnumerable<RoutePatternPathSegment> segments)
+        {
+            if (segments == null)
+            {
+                throw new ArgumentNullException(nameof(segments));
+            }
+
+            return PatternCore(null, null, null, segments);
+        }
+
+        public static RoutePattern Pattern(string rawText, IEnumerable<RoutePatternPathSegment> segments)
+        {
+            if (segments == null)
+            {
+                throw new ArgumentNullException(nameof(segments));
+            }
+
+            return PatternCore(rawText, null, null, segments);
+        }
+
+        public static RoutePattern Pattern(
+            object defaults,
+            object constraints,
+            IEnumerable<RoutePatternPathSegment> segments)
+        {
+            if (segments == null)
+            {
+                throw new ArgumentNullException(nameof(segments));
+            }
+
+            return PatternCore(null, new RouteValueDictionary(defaults), new RouteValueDictionary(constraints), segments);
+        }
+
+        public static RoutePattern Pattern(
+            string rawText,
+            object defaults,
+            object constraints,
+            IEnumerable<RoutePatternPathSegment> segments)
+        {
+            if (segments == null)
+            {
+                throw new ArgumentNullException(nameof(segments));
+            }
+
+            return PatternCore(rawText, new RouteValueDictionary(defaults), new RouteValueDictionary(constraints), segments);
+        }
+
+        public static RoutePattern Pattern(params RoutePatternPathSegment[] segments)
+        {
+            if (segments == null)
+            {
+                throw new ArgumentNullException(nameof(segments));
+            }
+
+            return PatternCore(null, null, null, segments);
+        }
+
+        public static RoutePattern Pattern(string rawText, params RoutePatternPathSegment[] segments)
+        {
+            if (segments == null)
+            {
+                throw new ArgumentNullException(nameof(segments));
+            }
+
+            return PatternCore(rawText, null, null, segments);
+        }
+
+        public static RoutePattern Pattern(
+            object defaults,
+            object constraints,
+            params RoutePatternPathSegment[] segments)
+        {
+            if (segments == null)
+            {
+                throw new ArgumentNullException(nameof(segments));
+            }
+
+            return PatternCore(null, new RouteValueDictionary(defaults), new RouteValueDictionary(constraints), segments);
+        }
+
+        public static RoutePattern Pattern(
+            string rawText,
+            object defaults,
+            object constraints,
+            params RoutePatternPathSegment[] segments)
+        {
+            if (segments == null)
+            {
+                throw new ArgumentNullException(nameof(segments));
+            }
+
+            return PatternCore(rawText, new RouteValueDictionary(defaults), new RouteValueDictionary(constraints), segments);
+        }
+
+        private static RoutePattern PatternCore(
+            string rawText,
+            IDictionary<string, object> defaults,
+            IDictionary<string, object> constraints,
+            IEnumerable<RoutePatternPathSegment> segments)
+        {
+            // We want to merge the segment data with the 'out of line' defaults and constraints.
+            //
+            // This means that for parameters that have 'out of line' defaults we will modify
+            // the parameter to contain the default (same story for constraints).
+            //
+            // We also maintain a collection of defaults and constraints that will also
+            // contain the values that don't match a parameter.
+            //
+            // It's important that these two views of the data are consistent. We don't want
+            // values specified out of line to have a different behavior.
+
+            var updatedDefaults = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
+            if (defaults != null)
+            {
+                foreach (var kvp in defaults)
+                {
+                    updatedDefaults.Add(kvp.Key, kvp.Value);
+                }
+            }
+
+            var updatedConstraints = new Dictionary<string, List<RoutePatternConstraintReference>>(StringComparer.OrdinalIgnoreCase);
+            if (constraints != null)
+            {
+                foreach (var kvp in constraints)
+                {
+                    updatedConstraints.Add(kvp.Key, new List<RoutePatternConstraintReference>()
+                    {
+                        Constraint(kvp.Key, kvp.Value),
+                    });
+                }
+            }
+
+            var parameters = new List<RoutePatternParameterPart>();
+            var updatedSegments = segments.ToArray();
+            for (var i = 0; i < updatedSegments.Length; i++)
+            {
+                var segment = VisitSegment(updatedSegments[i]);
+                updatedSegments[i] = segment;
+                
+                for (var j = 0; j < segment.Parts.Count; j++)
+                {
+                    if (segment.Parts[j] is RoutePatternParameterPart parameter)
+                    {
+                        parameters.Add(parameter);
+                    }
+                }
+            }
+
+            return new RoutePattern(
+                rawText,
+                updatedDefaults,
+                updatedConstraints.ToDictionary(kvp => kvp.Key, kvp => (IReadOnlyList<RoutePatternConstraintReference>)kvp.Value.ToArray()),
+                parameters.ToArray(),
+                updatedSegments.ToArray());
+
+            RoutePatternPathSegment VisitSegment(RoutePatternPathSegment segment)
+            {
+                var updatedParts = new RoutePatternPart[segment.Parts.Count];
+                for (var i = 0; i < segment.Parts.Count; i++)
+                {
+                    var part = segment.Parts[i];
+                    updatedParts[i] = VisitPart(part);
+                }
+
+                return SegmentCore(updatedParts);
+            }
+
+            RoutePatternPart VisitPart(RoutePatternPart part)
+            {
+                if (!part.IsParameter)
+                {
+                    return part;
+                }
+
+                var parameter = (RoutePatternParameterPart)part;
+                var @default = parameter.Default;
+
+                if (updatedDefaults.TryGetValue(parameter.Name, out var newDefault))
+                {
+                    if (parameter.Default != null)
+                    {
+                        var message = Resources.FormatTemplateRoute_CannotHaveDefaultValueSpecifiedInlineAndExplicitly(parameter.Name);
+                        throw new InvalidOperationException(message);
+                    }
+
+                    if (parameter.IsOptional)
+                    {
+                        var message = Resources.TemplateRoute_OptionalCannotHaveDefaultValue;
+                        throw new InvalidOperationException(message);
+                    }
+
+                    @default = newDefault;
+                }
+                
+                if (parameter.Default != null)
+                {
+                    updatedDefaults.Add(parameter.Name, parameter.Default);
+                }
+
+                if (!updatedConstraints.TryGetValue(parameter.Name, out var parameterConstraints) &&
+                    parameter.Constraints.Count > 0)
+                {
+                    parameterConstraints = new List<RoutePatternConstraintReference>();
+                    updatedConstraints.Add(parameter.Name, parameterConstraints);
+                }
+
+                if (parameter.Constraints.Count > 0)
+                {
+                    parameterConstraints.AddRange(parameter.Constraints);
+                }
+
+                return ParameterPartCore(
+                    parameter.Name,
+                    @default,
+                    parameter.ParameterKind,
+                    (IEnumerable<RoutePatternConstraintReference>)parameterConstraints ?? Array.Empty<RoutePatternConstraintReference>());
+            }
+        }
+
+        public static RoutePatternPathSegment Segment(IEnumerable<RoutePatternPart> parts)
+        {
+            if (parts == null)
+            {
+                throw new ArgumentNullException(nameof(parts));
+            }
+
+            return SegmentCore(parts);
+        }
+
+        public static RoutePatternPathSegment Segment(params RoutePatternPart[] parts)
+        {
+            if (parts == null)
+            {
+                throw new ArgumentNullException(nameof(parts));
+            }
+
+            return SegmentCore(parts);
+        }
+
+        private static RoutePatternPathSegment SegmentCore(IEnumerable<RoutePatternPart> parts)
+        {
+            return new RoutePatternPathSegment(parts.ToArray());
+        }
+
+        public static RoutePatternLiteralPart LiteralPart(string content)
+        {
+            if (string.IsNullOrEmpty(content))
+            {
+                throw new ArgumentException(Resources.Argument_NullOrEmpty, nameof(content));
+            }
+
+            if (content.IndexOf('?') >= 0)
+            {
+                throw new ArgumentException(Resources.FormatTemplateRoute_InvalidLiteral(content));
+            }
+
+            return LiteralPartCore(content);
+        }
+
+        private static RoutePatternLiteralPart LiteralPartCore(string content)
+        {
+            return new RoutePatternLiteralPart(content);
+        }
+
+        public static RoutePatternSeparatorPart SeparatorPart(string content)
+        {
+            if (string.IsNullOrEmpty(content))
+            {
+                throw new ArgumentException(Resources.Argument_NullOrEmpty, nameof(content));
+            }
+
+            return SeparatorPartCore(content);
+        }
+
+        private static RoutePatternSeparatorPart SeparatorPartCore(string content)
+        {
+            return new RoutePatternSeparatorPart(content);
+        }
+
+        public static RoutePatternParameterPart ParameterPart(string parameterName)
+        {
+            if (string.IsNullOrEmpty(parameterName))
+            {
+                throw new ArgumentException(Resources.Argument_NullOrEmpty, nameof(parameterName));
+            }
+
+            if (parameterName.IndexOfAny(RoutePatternParser.InvalidParameterNameChars) >= 0)
+            {
+                throw new ArgumentException(Resources.FormatTemplateRoute_InvalidParameterName(parameterName));
+            }
+
+            return ParameterPartCore(
+                parameterName: parameterName,
+                @default: null,
+                parameterKind: RoutePatternParameterKind.Standard,
+                constraints: Array.Empty<RoutePatternConstraintReference>());
+        }
+        
+        public static RoutePatternParameterPart ParameterPart(string parameterName, object @default)
+        {
+            if (string.IsNullOrEmpty(parameterName))
+            {
+                throw new ArgumentException(Resources.Argument_NullOrEmpty, nameof(parameterName));
+            }
+
+            if (parameterName.IndexOfAny(RoutePatternParser.InvalidParameterNameChars) >= 0)
+            {
+                throw new ArgumentException(Resources.FormatTemplateRoute_InvalidParameterName(parameterName));
+            }
+
+            return ParameterPartCore(
+                parameterName: parameterName,
+                @default: @default,
+                parameterKind: RoutePatternParameterKind.Standard,
+                constraints: Array.Empty<RoutePatternConstraintReference>());
+        }
+
+        public static RoutePatternParameterPart ParameterPart(
+            string parameterName,
+            object @default,
+            RoutePatternParameterKind parameterKind)
+        {
+            if (string.IsNullOrEmpty(parameterName))
+            {
+                throw new ArgumentException(Resources.Argument_NullOrEmpty, nameof(parameterName));
+            }
+
+            if (parameterName.IndexOfAny(RoutePatternParser.InvalidParameterNameChars) >= 0)
+            {
+                throw new ArgumentException(Resources.FormatTemplateRoute_InvalidParameterName(parameterName));
+            }
+
+            if (@default != null && parameterKind == RoutePatternParameterKind.Optional)
+            {
+                throw new ArgumentNullException(Resources.TemplateRoute_OptionalCannotHaveDefaultValue, nameof(parameterKind));
+            }
+
+            return ParameterPartCore(
+                parameterName: parameterName,
+                @default: @default,
+                parameterKind: parameterKind,
+                constraints: Array.Empty<RoutePatternConstraintReference>());
+        }
+
+        public static RoutePatternParameterPart ParameterPart(
+            string parameterName,
+            object @default,
+            RoutePatternParameterKind parameterKind,
+            IEnumerable<RoutePatternConstraintReference> constraints)
+        {
+            if (string.IsNullOrEmpty(parameterName))
+            {
+                throw new ArgumentException(Resources.Argument_NullOrEmpty, nameof(parameterName));
+            }
+
+            if (parameterName.IndexOfAny(RoutePatternParser.InvalidParameterNameChars) >= 0)
+            {
+                throw new ArgumentException(Resources.FormatTemplateRoute_InvalidParameterName(parameterName));
+            }
+
+            if (@default != null && parameterKind == RoutePatternParameterKind.Optional)
+            {
+                throw new ArgumentNullException(Resources.TemplateRoute_OptionalCannotHaveDefaultValue, nameof(parameterKind));
+            }
+
+            if (constraints == null)
+            {
+                throw new ArgumentNullException(nameof(constraints));
+            }
+
+            return ParameterPartCore(
+                parameterName: parameterName,
+                @default: @default,
+                parameterKind: parameterKind,
+                constraints: constraints);
+        }
+
+        public static RoutePatternParameterPart ParameterPart(
+            string parameterName,
+            object @default,
+            RoutePatternParameterKind parameterKind,
+            params RoutePatternConstraintReference[] constraints)
+        {
+            if (string.IsNullOrEmpty(parameterName))
+            {
+                throw new ArgumentException(Resources.Argument_NullOrEmpty, nameof(parameterName));
+            }
+
+            if (parameterName.IndexOfAny(RoutePatternParser.InvalidParameterNameChars) >= 0)
+            {
+                throw new ArgumentException(Resources.FormatTemplateRoute_InvalidParameterName(parameterName));
+            }
+
+            if (@default != null && parameterKind == RoutePatternParameterKind.Optional)
+            {
+                throw new ArgumentNullException(Resources.TemplateRoute_OptionalCannotHaveDefaultValue, nameof(parameterKind));
+            }
+
+            if (constraints == null)
+            {
+                throw new ArgumentNullException(nameof(constraints));
+            }
+
+            return ParameterPartCore(
+                parameterName: parameterName,
+                @default: @default,
+                parameterKind: parameterKind,
+                constraints: constraints);
+        }
+
+        private static RoutePatternParameterPart ParameterPartCore(
+            string parameterName,
+            object @default,
+            RoutePatternParameterKind parameterKind,
+            IEnumerable<RoutePatternConstraintReference> constraints)
+        {
+            return new RoutePatternParameterPart(parameterName, @default, parameterKind, constraints.ToArray());
+        }
+
+        public static RoutePatternConstraintReference Constraint(string parameterName, object constraint)
+        {
+            // Similar to RouteConstraintBuilder
+            if (constraint is IRouteConstraint routeConstraint)
+            {
+                return ConstraintCore(parameterName, routeConstraint);
+            }
+            else if (constraint is string content)
+            {
+                return ConstraintCore(parameterName, new RegexRouteConstraint("^(" + content + ")$"));
+            }
+            else
+            {
+                throw new InvalidOperationException(Resources.FormatConstraintMustBeStringOrConstraint(
+                    parameterName,
+                    constraint,
+                    typeof(IRouteConstraint)));
+            }
+        }
+
+        public static RoutePatternConstraintReference Constraint(string parameterName, IRouteConstraint constraint)
+        {
+            if (constraint == null)
+            {
+                throw new ArgumentNullException(nameof(constraint));
+            }
+
+            return ConstraintCore(parameterName, constraint);
+        }
+
+        public static RoutePatternConstraintReference Constraint(string parameterName, string constraint)
+        {
+            if (string.IsNullOrEmpty(constraint))
+            {
+                throw new ArgumentException(Resources.Argument_NullOrEmpty, nameof(constraint));
+            }
+
+            return ConstraintCore(parameterName, constraint);
+        }
+
+
+        private static RoutePatternConstraintReference ConstraintCore(string parameterName, IRouteConstraint constraint)
+        {
+            return new RoutePatternConstraintReference(parameterName, constraint);
+        }
+
+        private static RoutePatternConstraintReference ConstraintCore(string parameterName, string constraint)
+        {
+            return new RoutePatternConstraintReference(parameterName, constraint);
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternLiteralPart.cs

@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Diagnostics;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    [DebuggerDisplay("{DebuggerToString()}")]
+    public sealed class RoutePatternLiteralPart : RoutePatternPart
+    {
+        internal RoutePatternLiteralPart(string content)
+            : base(RoutePatternPartKind.Literal)
+        {
+            Debug.Assert(!string.IsNullOrEmpty(content));
+            Content = content;
+        }
+
+        public string Content { get; }
+
+        internal override string DebuggerToString()
+        {
+            return Content;
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternMatcher.cs

@@ -0,0 +1,511 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using Microsoft.AspNetCore.Routing.Internal;
+using Microsoft.AspNetCore.Routing.Patterns;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Primitives;
+
+namespace Microsoft.AspNetCore.Routing
+{
+    public class RoutePatternMatcher
+    {
+        private const string SeparatorString = "/";
+        private const char SeparatorChar = '/';
+
+        // Perf: This is a cache to avoid looking things up in 'Defaults' each request.
+        private readonly bool[] _hasDefaultValue;
+        private readonly object[] _defaultValues;
+
+        private static readonly char[] Delimiters = new char[] { SeparatorChar };
+
+        public RoutePatternMatcher(
+            RoutePattern pattern,
+            RouteValueDictionary defaults)
+        {
+            if (pattern == null)
+            {
+                throw new ArgumentNullException(nameof(pattern));
+            }
+
+            RoutePattern = pattern;
+            Defaults = defaults ?? new RouteValueDictionary();
+
+            // Perf: cache the default value for each parameter (other than complex segments).
+            _hasDefaultValue = new bool[RoutePattern.PathSegments.Count];
+            _defaultValues = new object[RoutePattern.PathSegments.Count];
+
+            for (var i = 0; i < RoutePattern.PathSegments.Count; i++)
+            {
+                var segment = RoutePattern.PathSegments[i];
+                if (!segment.IsSimple)
+                {
+                    continue;
+                }
+
+                var part = segment.Parts[0];
+                if (!part.IsParameter)
+                {
+                    continue;
+                }
+
+                var parameter = (RoutePatternParameterPart)part;
+                if (Defaults.TryGetValue(parameter.Name, out var value))
+                {
+                    _hasDefaultValue[i] = true;
+                    _defaultValues[i] = value;
+                }
+            }
+        }
+
+        public RouteValueDictionary Defaults { get; }
+
+        public RoutePattern RoutePattern { get; }
+
+        public bool TryMatch(PathString path, RouteValueDictionary values)
+        {
+            if (values == null)
+            {
+                throw new ArgumentNullException(nameof(values));
+            }
+
+            var i = 0;
+            var pathTokenizer = new PathTokenizer(path);
+
+            // Perf: We do a traversal of the request-segments + route-segments twice.
+            //
+            // For most segment-types, we only really need to any work on one of the two passes.
+            //
+            // On the first pass, we're just looking to see if there's anything that would disqualify us from matching.
+            // The most common case would be a literal segment that doesn't match.
+            //
+            // On the second pass, we're almost certainly going to match the URL, so go ahead and allocate the 'values'
+            // and start capturing strings. 
+            foreach (var stringSegment in pathTokenizer)
+            {
+                if (stringSegment.Length == 0)
+                {
+                    return false;
+                }
+
+                var pathSegment = i >= RoutePattern.PathSegments.Count ? null : RoutePattern.PathSegments[i];
+                if (pathSegment == null && stringSegment.Length > 0)
+                {
+                    // If pathSegment is null, then we're out of route segments. All we can match is the empty
+                    // string.
+                    return false;
+                }
+                else if (pathSegment.IsSimple && pathSegment.Parts[0] is RoutePatternParameterPart parameter && parameter.IsCatchAll)
+                {
+                    // Nothing to validate for a catch-all - it can match any string, including the empty string.
+                    //
+                    // Also, a catch-all has to be the last part, so we're done.
+                    break;
+                }
+                if (!TryMatchLiterals(i++, stringSegment, pathSegment))
+                {
+                    return false;
+                }
+            }
+
+            for (; i < RoutePattern.PathSegments.Count; i++)
+            {
+                // We've matched the request path so far, but still have remaining route segments. These need
+                // to be all single-part parameter segments with default values or else they won't match.
+                var pathSegment = RoutePattern.PathSegments[i];
+                Debug.Assert(pathSegment != null);
+
+                if (!pathSegment.IsSimple)
+                {
+                    // If the segment is a complex segment, it MUST contain literals, and we've parsed the full
+                    // path so far, so it can't match.
+                    return false;
+                }
+
+                var part = pathSegment.Parts[0];
+                if (part.IsLiteral || part.IsSeparator)
+                {
+                    // If the segment is a simple literal - which need the URL to provide a value, so we don't match.
+                    return false;
+                }
+
+                var parameter = (RoutePatternParameterPart)part;
+                if (parameter.IsCatchAll)
+                {
+                    // Nothing to validate for a catch-all - it can match any string, including the empty string.
+                    //
+                    // Also, a catch-all has to be the last part, so we're done.
+                    break;
+                }
+
+                // If we get here, this is a simple segment with a parameter. We need it to be optional, or for the
+                // defaults to have a value.
+                if (!_hasDefaultValue[i] && !parameter.IsOptional)
+                {
+                    // There's no default for this (non-optional) parameter so it can't match.
+                    return false;
+                }
+            }
+
+            // At this point we've very likely got a match, so start capturing values for real.
+            i = 0;
+            foreach (var requestSegment in pathTokenizer)
+            {
+                var pathSegment = RoutePattern.PathSegments[i++];
+                if (SavePathSegmentsAsValues(i, values, requestSegment, pathSegment))
+                {
+                    break;
+                }
+                if (!pathSegment.IsSimple)
+                {
+                    if (!MatchComplexSegment(pathSegment, requestSegment.ToString(), Defaults, values))
+                    {
+                        return false;
+                    }
+                }
+            }
+
+            for (; i < RoutePattern.PathSegments.Count; i++)
+            {
+                // We've matched the request path so far, but still have remaining route segments. We already know these
+                // are simple parameters that either have a default, or don't need to produce a value.
+                var pathSegment = RoutePattern.PathSegments[i];
+                Debug.Assert(pathSegment != null);
+                Debug.Assert(pathSegment.IsSimple);
+
+                var part = pathSegment.Parts[0];
+                Debug.Assert(part.IsParameter);
+
+                // It's ok for a catch-all to produce a null value
+                if (part is RoutePatternParameterPart parameter && (parameter.IsCatchAll || _hasDefaultValue[i]))
+                {
+                    // Don't replace an existing value with a null.
+                    var defaultValue = _defaultValues[i];
+                    if (defaultValue != null || !values.ContainsKey(parameter.Name))
+                    {
+                        values[parameter.Name] = defaultValue;
+                    }
+                }
+            }
+
+            // Copy all remaining default values to the route data
+            foreach (var kvp in Defaults)
+            {
+                if (!values.ContainsKey(kvp.Key))
+                {
+                    values.Add(kvp.Key, kvp.Value);
+                }
+            }
+
+            return true;
+        }
+
+        private bool TryMatchLiterals(int index, StringSegment stringSegment, RoutePatternPathSegment pathSegment)
+        {
+            if (pathSegment.IsSimple && !pathSegment.Parts[0].IsParameter)
+            {
+                // This is a literal segment, so we need to match the text, or the route isn't a match.
+                if (pathSegment.Parts[0].IsLiteral)
+                {
+                    var part = (RoutePatternLiteralPart)pathSegment.Parts[0];
+
+                    if (!stringSegment.Equals(part.Content, StringComparison.OrdinalIgnoreCase))
+                    {
+                        return false;
+                    }
+                }
+                else
+                {
+                    var part = (RoutePatternSeparatorPart)pathSegment.Parts[0];
+
+                    if (!stringSegment.Equals(part.Content, StringComparison.OrdinalIgnoreCase))
+                    {
+                        return false;
+                    }
+                }
+            }
+            else if (pathSegment.IsSimple && pathSegment.Parts[0].IsParameter)
+            {
+                // For a parameter, validate that it's a has some length, or we have a default, or it's optional.
+                var part = (RoutePatternParameterPart)pathSegment.Parts[0];
+                if (stringSegment.Length == 0 &&
+                    !_hasDefaultValue[index] &&
+                    !part.IsOptional)
+                {
+                    // There's no value for this parameter, the route can't match.
+                    return false;
+                }
+            }
+            else
+            {
+                Debug.Assert(!pathSegment.IsSimple);
+                // Don't attempt to validate a complex segment at this point other than being non-emtpy,
+                // do it in the second pass.
+            }
+            return true;
+        }
+
+        private bool SavePathSegmentsAsValues(int index, RouteValueDictionary values, StringSegment requestSegment, RoutePatternPathSegment pathSegment)
+        {
+            if (pathSegment.IsSimple && pathSegment.Parts[0] is RoutePatternParameterPart parameter && parameter.IsCatchAll)
+            {
+                // A catch-all captures til the end of the string.
+                var captured = requestSegment.Buffer.Substring(requestSegment.Offset);
+                if (captured.Length > 0)
+                {
+                    values[parameter.Name] = captured;
+                }
+                else
+                {
+                    // It's ok for a catch-all to produce a null value, so we don't check _hasDefaultValue.
+                    values[parameter.Name] = _defaultValues[index];
+                }
+
+                // A catch-all has to be the last part, so we're done.
+                return true;
+            }
+            else if (pathSegment.IsSimple && pathSegment.Parts[0].IsParameter)
+            {
+                // A simple parameter captures the whole segment, or a default value if nothing was
+                // provided.
+                parameter = (RoutePatternParameterPart)pathSegment.Parts[0];
+                if (requestSegment.Length > 0)
+                {
+                    values[parameter.Name] = requestSegment.ToString();
+                }
+                else
+                {
+                    if (_hasDefaultValue[index])
+                    {
+                        values[parameter.Name] = _defaultValues[index];
+                    }
+                }
+            }
+            return false;
+        }
+
+        private bool MatchComplexSegment(
+            RoutePatternPathSegment routeSegment,
+            string requestSegment,
+            IReadOnlyDictionary<string, object> defaults,
+            RouteValueDictionary values)
+        {
+            var indexOfLastSegment = routeSegment.Parts.Count - 1;
+
+            // We match the request to the template starting at the rightmost parameter
+            // If the last segment of template is optional, then request can match the 
+            // template with or without the last parameter. So we start with regular matching,
+            // but if it doesn't match, we start with next to last parameter. Example:
+            // Template: {p1}/{p2}.{p3?}. If the request is one/two.three it will match right away
+            // giving p3 value of three. But if the request is one/two, we start matching from the
+            // rightmost giving p3 the value of two, then we end up not matching the segment.
+            // In this case we start again from p2 to match the request and we succeed giving
+            // the value two to p2
+            if (routeSegment.Parts[indexOfLastSegment] is RoutePatternParameterPart parameter && parameter.IsOptional &&
+                routeSegment.Parts[indexOfLastSegment - 1].IsSeparator)
+            {
+                if (MatchComplexSegmentCore(routeSegment, requestSegment, Defaults, values, indexOfLastSegment))
+                {
+                    return true;
+                }
+                else
+                {
+                    var separator = (RoutePatternSeparatorPart)routeSegment.Parts[indexOfLastSegment - 1];
+                    if (requestSegment.EndsWith(
+                    separator.Content,
+                    StringComparison.OrdinalIgnoreCase))
+                        return false;
+
+                    return MatchComplexSegmentCore(
+                        routeSegment,
+                        requestSegment,
+                        Defaults,
+                        values,
+                        indexOfLastSegment - 2);
+                }
+            }
+            else
+            {
+                return MatchComplexSegmentCore(routeSegment, requestSegment, Defaults, values, indexOfLastSegment);
+            }
+        }
+
+        private bool MatchComplexSegmentCore(
+            RoutePatternPathSegment routeSegment,
+            string requestSegment,
+            IReadOnlyDictionary<string, object> defaults,
+            RouteValueDictionary values,
+            int indexOfLastSegmentUsed)
+        {
+            Debug.Assert(routeSegment != null);
+            Debug.Assert(routeSegment.Parts.Count > 1);
+
+            // Find last literal segment and get its last index in the string
+            var lastIndex = requestSegment.Length;
+
+            RoutePatternParameterPart parameterNeedsValue = null; // Keeps track of a parameter segment that is pending a value
+            RoutePatternPart lastLiteral = null; // Keeps track of the left-most literal we've encountered
+
+            var outValues = new RouteValueDictionary();
+
+            while (indexOfLastSegmentUsed >= 0)
+            {
+                var newLastIndex = lastIndex;
+
+                var part = routeSegment.Parts[indexOfLastSegmentUsed];
+                if (part.IsParameter)
+                {
+                    // Hold on to the parameter so that we can fill it in when we locate the next literal
+                    parameterNeedsValue = (RoutePatternParameterPart)part;
+                }
+                else
+                {
+                    Debug.Assert(part.IsLiteral || part.IsSeparator);
+                    lastLiteral = part;
+
+                    var startIndex = lastIndex - 1;
+                    // If we have a pending parameter subsegment, we must leave at least one character for that
+                    if (parameterNeedsValue != null)
+                    {
+                        startIndex--;
+                    }
+
+                    if (startIndex < 0)
+                    {
+                        return false;
+                    }
+
+                    int indexOfLiteral;
+                    if (part.IsLiteral)
+                    {
+                        var literal = (RoutePatternLiteralPart)part;
+                        indexOfLiteral = requestSegment.LastIndexOf(
+                        literal.Content,
+                        startIndex,
+                        StringComparison.OrdinalIgnoreCase);
+                    }
+                    else
+                    {
+                        var literal = (RoutePatternSeparatorPart)part;
+                        indexOfLiteral = requestSegment.LastIndexOf(
+                        literal.Content,
+                        startIndex,
+                        StringComparison.OrdinalIgnoreCase);
+                    }
+
+                    if (indexOfLiteral == -1)
+                    {
+                        // If we couldn't find this literal index, this segment cannot match
+                        return false;
+                    }
+
+                    // If the first subsegment is a literal, it must match at the right-most extent of the request URI.
+                    // Without this check if your route had "/Foo/" we'd match the request URI "/somethingFoo/".
+                    // This check is related to the check we do at the very end of this function.
+                    if (indexOfLastSegmentUsed == (routeSegment.Parts.Count - 1))
+                    {
+                        if (part is RoutePatternLiteralPart literal && ((indexOfLiteral + literal.Content.Length) != requestSegment.Length))
+                        {
+                            return false;
+                        }
+                        else if (part is RoutePatternSeparatorPart separator && ((indexOfLiteral + separator.Content.Length) != requestSegment.Length))
+                        {
+                            return false;
+                        }
+                    }
+
+                    newLastIndex = indexOfLiteral;
+                }
+
+                if ((parameterNeedsValue != null) &&
+                    (((lastLiteral != null) && !part.IsParameter) || (indexOfLastSegmentUsed == 0)))
+                {
+                    // If we have a pending parameter that needs a value, grab that value
+
+                    int parameterStartIndex;
+                    int parameterTextLength;
+
+                    if (lastLiteral == null)
+                    {
+                        if (indexOfLastSegmentUsed == 0)
+                        {
+                            parameterStartIndex = 0;
+                        }
+                        else
+                        {
+                            parameterStartIndex = newLastIndex;
+                            Debug.Assert(false, "indexOfLastSegementUsed should always be 0 from the check above");
+                        }
+                        parameterTextLength = lastIndex;
+                    }
+                    else
+                    {
+                        // If we're getting a value for a parameter that is somewhere in the middle of the segment
+                        if ((indexOfLastSegmentUsed == 0) && (part.IsParameter))
+                        {
+                            parameterStartIndex = 0;
+                            parameterTextLength = lastIndex;
+                        }
+                        else
+                        {
+                            if (lastLiteral.IsLiteral)
+                            {
+                                var literal = (RoutePatternLiteralPart)lastLiteral;
+                                parameterStartIndex = newLastIndex + literal.Content.Length;
+                            }
+                            else
+                            {
+                                var separator = (RoutePatternSeparatorPart)lastLiteral;
+                                parameterStartIndex = newLastIndex + separator.Content.Length;
+                            }
+                            parameterTextLength = lastIndex - parameterStartIndex;
+                        }
+                    }
+
+                    var parameterValueString = requestSegment.Substring(parameterStartIndex, parameterTextLength);
+
+                    if (string.IsNullOrEmpty(parameterValueString))
+                    {
+                        // If we're here that means we have a segment that contains multiple sub-segments.
+                        // For these segments all parameters must have non-empty values. If the parameter
+                        // has an empty value it's not a match.                        
+                        return false;
+
+                    }
+                    else
+                    {
+                        // If there's a value in the segment for this parameter, use the subsegment value
+                        outValues.Add(parameterNeedsValue.Name, parameterValueString);
+                    }
+
+                    parameterNeedsValue = null;
+                    lastLiteral = null;
+                }
+
+                lastIndex = newLastIndex;
+                indexOfLastSegmentUsed--;
+            }
+
+            // If the last subsegment is a parameter, it's OK that we didn't parse all the way to the left extent of
+            // the string since the parameter will have consumed all the remaining text anyway. If the last subsegment
+            // is a literal then we *must* have consumed the entire text in that literal. Otherwise we end up matching
+            // the route "Foo" to the request URI "somethingFoo". Thus we have to check that we parsed the *entire*
+            // request URI in order for it to be a match.
+            // This check is related to the check we do earlier in this function for LiteralSubsegments.
+            if (lastIndex == 0 || routeSegment.Parts[0].IsParameter)
+            {
+                foreach (var item in outValues)
+                {
+                    values.Add(item.Key, item.Value);
+                }
+
+                return true;
+            }
+
+            return false;
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternParameterKind.cs

@@ -0,0 +1,12 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    public enum RoutePatternParameterKind
+    {
+        Standard,
+        Optional,
+        CatchAll,
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternParameterPart.cs

@@ -0,0 +1,73 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    [DebuggerDisplay("{DebuggerToString()}")]
+    public class RoutePatternParameterPart : RoutePatternPart
+    {
+        internal RoutePatternParameterPart(
+            string parameterName,
+            object @default,
+            RoutePatternParameterKind parameterKind,
+            RoutePatternConstraintReference[] constraints)
+            : base(RoutePatternPartKind.Parameter)
+        {
+            // See #475 - this code should have some asserts, but it can't because of the design of RouteParameterParser.
+
+            Name = parameterName;
+            Default = @default;
+            ParameterKind = parameterKind;
+            Constraints = constraints;
+        }
+
+        public IReadOnlyList<RoutePatternConstraintReference> Constraints { get; }
+
+        public object Default { get; }
+
+        public bool IsCatchAll => ParameterKind == RoutePatternParameterKind.CatchAll;
+
+        public bool IsOptional => ParameterKind == RoutePatternParameterKind.Optional;
+
+        public RoutePatternParameterKind ParameterKind { get; }
+
+        public string Name { get; }
+
+        internal override string DebuggerToString()
+        {
+            var builder = new StringBuilder();
+            builder.Append("{");
+
+            if (IsCatchAll)
+            {
+                builder.Append("*");
+            }
+
+            builder.Append(Name);
+
+            foreach (var constraint in Constraints)
+            {
+                builder.Append(":");
+                builder.Append(constraint.Constraint);
+            }
+
+            if (Default != null)
+            {
+                builder.Append("=");
+                builder.Append(Default);
+            }
+
+            if (IsOptional)
+            {
+                builder.Append("?");
+            }
+
+            builder.Append("}");
+            return builder.ToString();
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternParser.cs

@@ -0,0 +1,577 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    internal static class RoutePatternParser
+    {
+        private const char Separator = '/';
+        private const char OpenBrace = '{';
+        private const char CloseBrace = '}';
+        private const char EqualsSign = '=';
+        private const char QuestionMark = '?';
+        private const char Asterisk = '*';
+        private const string PeriodString = ".";
+
+        internal static readonly char[] InvalidParameterNameChars = new char[]
+        {
+            Separator,
+            OpenBrace,
+            CloseBrace,
+            QuestionMark,
+            Asterisk
+        };
+
+        public static RoutePattern Parse(string pattern)
+        {
+            if (pattern == null)
+            {
+                throw new ArgumentNullException(nameof(pattern));
+            }
+
+            var trimmedPattern = TrimPrefix(pattern);
+
+            var context = new Context(trimmedPattern);
+            var segments = new List<RoutePatternPathSegment>();
+
+            while (context.MoveNext())
+            {
+                var i = context.Index;
+
+                if (context.Current == Separator)
+                {
+                    // If we get here is means that there's a consecutive '/' character.
+                    // Templates don't start with a '/' and parsing a segment consumes the separator.
+                    throw new RoutePatternException(pattern, Resources.TemplateRoute_CannotHaveConsecutiveSeparators);
+                }
+
+                if (!ParseSegment(context, segments))
+                {
+                    throw new RoutePatternException(pattern, context.Error);
+                }
+
+                // A successful parse should always result in us being at the end or at a separator.
+                Debug.Assert(context.AtEnd() || context.Current == Separator);
+
+                if (context.Index <= i)
+                {
+                    // This shouldn't happen, but we want to crash if it does.
+                    var message = "Infinite loop detected in the parser. Please open an issue.";
+                    throw new InvalidProgramException(message);
+                }
+            }
+
+            if (IsAllValid(context, segments))
+            {
+                return RoutePatternFactory.Pattern(pattern, segments);
+            }
+            else
+            {
+                throw new RoutePatternException(pattern, context.Error);
+            }
+        }
+
+        private static bool ParseSegment(Context context, List<RoutePatternPathSegment> segments)
+        {
+            Debug.Assert(context != null);
+            Debug.Assert(segments != null);
+
+            var parts = new List<RoutePatternPart>();
+
+            while (true)
+            {
+                var i = context.Index;
+
+                if (context.Current == OpenBrace)
+                {
+                    if (!context.MoveNext())
+                    {
+                        // This is a dangling open-brace, which is not allowed
+                        context.Error = Resources.TemplateRoute_MismatchedParameter;
+                        return false;
+                    }
+
+                    if (context.Current == OpenBrace)
+                    {
+                        // This is an 'escaped' brace in a literal, like "{{foo"
+                        context.Back();
+                        if (!ParseLiteral(context, parts))
+                        {
+                            return false;
+                        }
+                    }
+                    else
+                    {
+                        // This is a parameter
+                        context.Back();
+                        if (!ParseParameter(context, parts))
+                        {
+                            return false;
+                        }
+                    }
+                }
+                else
+                {
+                    if (!ParseLiteral(context, parts))
+                    {
+                        return false;
+                    }
+                }
+
+                if (context.Current == Separator || context.AtEnd())
+                {
+                    // We've reached the end of the segment
+                    break;
+                }
+
+                if (context.Index <= i)
+                {
+                    // This shouldn't happen, but we want to crash if it does.
+                    var message = "Infinite loop detected in the parser. Please open an issue.";
+                    throw new InvalidProgramException(message);
+                }
+            }
+
+            if (IsSegmentValid(context, parts))
+            {
+                segments.Add(new RoutePatternPathSegment(parts.ToArray()));
+                return true;
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        private static bool ParseParameter(Context context, List<RoutePatternPart> parts)
+        {
+            Debug.Assert(context.Current == OpenBrace);
+            context.Mark();
+
+            context.MoveNext();
+
+            while (true)
+            {
+                if (context.Current == OpenBrace)
+                {
+                    // This is an open brace inside of a parameter, it has to be escaped
+                    if (context.MoveNext())
+                    {
+                        if (context.Current != OpenBrace)
+                        {
+                            // If we see something like "{p1:regex(^\d{3", we will come here.
+                            context.Error = Resources.TemplateRoute_UnescapedBrace;
+                            return false;
+                        }
+                    }
+                    else
+                    {
+                        // This is a dangling open-brace, which is not allowed
+                        // Example: "{p1:regex(^\d{"
+                        context.Error = Resources.TemplateRoute_MismatchedParameter;
+                        return false;
+                    }
+                }
+                else if (context.Current == CloseBrace)
+                {
+                    // When we encounter Closed brace here, it either means end of the parameter or it is a closed 
+                    // brace in the parameter, in that case it needs to be escaped.
+                    // Example: {p1:regex(([}}])\w+}. First pair is escaped one and last marks end of the parameter
+                    if (!context.MoveNext())
+                    {
+                        // This is the end of the string -and we have a valid parameter
+                        break;
+                    }
+
+                    if (context.Current == CloseBrace)
+                    {
+                        // This is an 'escaped' brace in a parameter name
+                    }
+                    else
+                    {
+                        // This is the end of the parameter
+                        break;
+                    }
+                }
+
+                if (!context.MoveNext())
+                {
+                    // This is a dangling open-brace, which is not allowed
+                    context.Error = Resources.TemplateRoute_MismatchedParameter;
+                    return false;
+                }
+            }
+
+            var text = context.Capture();
+            if (text == "{}")
+            {
+                context.Error = Resources.FormatTemplateRoute_InvalidParameterName(string.Empty);
+                return false;
+            }
+
+            var inside = text.Substring(1, text.Length - 2);
+            var decoded = inside.Replace("}}", "}").Replace("{{", "{");
+
+            // At this point, we need to parse the raw name for inline constraint,
+            // default values and optional parameters.
+            var templatePart = RouteParameterParser.ParseRouteParameter(decoded);
+
+            // See #475 - this is here because InlineRouteParameterParser can't return errors
+            if (decoded.StartsWith("*", StringComparison.Ordinal) && decoded.EndsWith("?", StringComparison.Ordinal))
+            {
+                context.Error = Resources.TemplateRoute_CatchAllCannotBeOptional;
+                return false;
+            }
+
+            if (templatePart.IsOptional && templatePart.Default != null)
+            {
+                // Cannot be optional and have a default value.
+                // The only way to declare an optional parameter is to have a ? at the end,
+                // hence we cannot have both default value and optional parameter within the template.
+                // A workaround is to add it as a separate entry in the defaults argument.
+                context.Error = Resources.TemplateRoute_OptionalCannotHaveDefaultValue;
+                return false;
+            }
+
+            var parameterName = templatePart.Name;
+            if (IsValidParameterName(context, parameterName))
+            {
+                parts.Add(templatePart);
+                return true;
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        private static bool ParseLiteral(Context context, List<RoutePatternPart> parts)
+        {
+            context.Mark();
+
+            while (true)
+            {
+                if (context.Current == Separator)
+                {
+                    // End of the segment
+                    break;
+                }
+                else if (context.Current == OpenBrace)
+                {
+                    if (!context.MoveNext())
+                    {
+                        // This is a dangling open-brace, which is not allowed
+                        context.Error = Resources.TemplateRoute_MismatchedParameter;
+                        return false;
+                    }
+
+                    if (context.Current == OpenBrace)
+                    {
+                        // This is an 'escaped' brace in a literal, like "{{foo" - keep going.
+                    }
+                    else
+                    {
+                        // We've just seen the start of a parameter, so back up.
+                        context.Back();
+                        break;
+                    }
+                }
+                else if (context.Current == CloseBrace)
+                {
+                    if (!context.MoveNext())
+                    {
+                        // This is a dangling close-brace, which is not allowed
+                        context.Error = Resources.TemplateRoute_MismatchedParameter;
+                        return false;
+                    }
+
+                    if (context.Current == CloseBrace)
+                    {
+                        // This is an 'escaped' brace in a literal, like "{{foo" - keep going.
+                    }
+                    else
+                    {
+                        // This is an unbalanced close-brace, which is not allowed
+                        context.Error = Resources.TemplateRoute_MismatchedParameter;
+                        return false;
+                    }
+                }
+
+                if (!context.MoveNext())
+                {
+                    break;
+                }
+            }
+
+            var encoded = context.Capture();
+            var decoded = encoded.Replace("}}", "}").Replace("{{", "{");
+            if (IsValidLiteral(context, decoded))
+            {
+                parts.Add(RoutePatternFactory.LiteralPart(decoded));
+                return true;
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        private static bool IsAllValid(Context context, List<RoutePatternPathSegment> segments)
+        {
+            // A catch-all parameter must be the last part of the last segment
+            for (var i = 0; i < segments.Count; i++)
+            {
+                var segment = segments[i];
+                for (var j = 0; j < segment.Parts.Count; j++)
+                {
+                    var part = segment.Parts[j];
+                    if (part is RoutePatternParameterPart parameter
+                        && parameter.IsCatchAll &&
+                        (i != segments.Count - 1 || j != segment.Parts.Count - 1))
+                    {
+                        context.Error = Resources.TemplateRoute_CatchAllMustBeLast;
+                        return false;
+                    }
+                }
+            }
+
+            return true;
+        }
+
+        private static bool IsSegmentValid(Context context, List<RoutePatternPart> parts)
+        {
+            // If a segment has multiple parts, then it can't contain a catch all.
+            for (var i = 0; i < parts.Count; i++)
+            {
+                var part = parts[i];
+                if (part is RoutePatternParameterPart parameter && parameter.IsCatchAll && parts.Count > 1)
+                {
+                    context.Error = Resources.TemplateRoute_CannotHaveCatchAllInMultiSegment;
+                    return false;
+                }
+            }
+
+            // if a segment has multiple parts, then only the last one parameter can be optional 
+            // if it is following a optional seperator. 
+            for (var i = 0; i < parts.Count; i++)
+            {
+                var part = parts[i];
+
+                if (part is RoutePatternParameterPart parameter && parameter.IsOptional && parts.Count > 1)
+                {
+                    // This optional parameter is the last part in the segment
+                    if (i == parts.Count - 1)
+                    {
+                        var previousPart = parts[i - 1];
+
+                        if (!previousPart.IsLiteral && !previousPart.IsSeparator)
+                        {
+                            // The optional parameter is preceded by something that is not a literal or separator
+                            // Example of error message:
+                            // "In the segment '{RouteValue}{param?}', the optional parameter 'param' is preceded
+                            // by an invalid segment '{RouteValue}'. Only a period (.) can precede an optional parameter.
+                            context.Error = string.Format(
+                                Resources.TemplateRoute_OptionalParameterCanbBePrecededByPeriod,
+                                RoutePatternPathSegment.DebuggerToString(parts),
+                                parameter.Name,
+                                parts[i - 1].DebuggerToString());
+
+                            return false;
+                        }
+                        else if (previousPart is RoutePatternLiteralPart literal && literal.Content != PeriodString)
+                        {
+                            // The optional parameter is preceded by a literal other than period.
+                            // Example of error message:
+                            // "In the segment '{RouteValue}-{param?}', the optional parameter 'param' is preceded
+                            // by an invalid segment '-'. Only a period (.) can precede an optional parameter.
+                            context.Error = string.Format(
+                                Resources.TemplateRoute_OptionalParameterCanbBePrecededByPeriod,
+                                RoutePatternPathSegment.DebuggerToString(parts),
+                                parameter.Name,
+                                parts[i - 1].DebuggerToString());
+
+                            return false;
+                        }
+
+                        parts[i - 1] = RoutePatternFactory.SeparatorPart(((RoutePatternLiteralPart)previousPart).Content);
+                    }
+                    else
+                    {
+                        // This optional parameter is not the last one in the segment
+                        // Example:
+                        // An optional parameter must be at the end of the segment. In the segment '{RouteValue?})', 
+                        // optional parameter 'RouteValue' is followed by ')'
+                        context.Error = string.Format(
+                            Resources.TemplateRoute_OptionalParameterHasTobeTheLast,
+                            RoutePatternPathSegment.DebuggerToString(parts),
+                            parameter.Name,
+                            parts[i + 1].DebuggerToString());
+
+                        return false;
+                    }
+                }
+            }
+
+            // A segment cannot contain two consecutive parameters
+            var isLastSegmentParameter = false;
+            for (var i = 0; i < parts.Count; i++)
+            {
+                var part = parts[i];
+                if (part.IsParameter && isLastSegmentParameter)
+                {
+                    context.Error = Resources.TemplateRoute_CannotHaveConsecutiveParameters;
+                    return false;
+                }
+
+                isLastSegmentParameter = part.IsParameter;
+            }
+
+            return true;
+        }
+
+        private static bool IsValidParameterName(Context context, string parameterName)
+        {
+            if (parameterName.Length == 0 || parameterName.IndexOfAny(InvalidParameterNameChars) >= 0)
+            {
+                context.Error = Resources.FormatTemplateRoute_InvalidParameterName(parameterName);
+                return false;
+            }
+
+            if (!context.ParameterNames.Add(parameterName))
+            {
+                context.Error = Resources.FormatTemplateRoute_RepeatedParameter(parameterName);
+                return false;
+            }
+
+            return true;
+        }
+
+        private static bool IsValidLiteral(Context context, string literal)
+        {
+            Debug.Assert(context != null);
+            Debug.Assert(literal != null);
+
+            if (literal.IndexOf(QuestionMark) != -1)
+            {
+                context.Error = Resources.FormatTemplateRoute_InvalidLiteral(literal);
+                return false;
+            }
+
+            return true;
+        }
+
+        private static string TrimPrefix(string routePattern)
+        {
+            if (routePattern.StartsWith("~/", StringComparison.Ordinal))
+            {
+                return routePattern.Substring(2);
+            }
+            else if (routePattern.StartsWith("/", StringComparison.Ordinal))
+            {
+                return routePattern.Substring(1);
+            }
+            else if (routePattern.StartsWith("~", StringComparison.Ordinal))
+            {
+                throw new RoutePatternException(routePattern, Resources.TemplateRoute_InvalidRouteTemplate);
+            }
+            return routePattern;
+        }
+
+        [DebuggerDisplay("{DebuggerToString()}")]
+        private class Context
+        {
+            private readonly string _template;
+            private int _index;
+            private int? _mark;
+
+            private readonly HashSet<string> _parameterNames = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
+            public Context(string template)
+            {
+                Debug.Assert(template != null);
+                _template = template;
+
+                _index = -1;
+            }
+
+            public char Current
+            {
+                get { return (_index < _template.Length && _index >= 0) ? _template[_index] : (char)0; }
+            }
+
+            public int Index => _index;
+
+            public string Error
+            {
+                get;
+                set;
+            }
+
+            public HashSet<string> ParameterNames
+            {
+                get { return _parameterNames; }
+            }
+
+            public bool Back()
+            {
+                return --_index >= 0;
+            }
+
+            public bool AtEnd()
+            {
+                return _index >= _template.Length;
+            }
+
+            public bool MoveNext()
+            {
+                return ++_index < _template.Length;
+            }
+
+            public void Mark()
+            {
+                Debug.Assert(_index >= 0);
+
+                // Index is always the index of the character *past* Current - we want to 'mark' Current.
+                _mark = _index;
+            }
+
+            public string Capture()
+            {
+                if (_mark.HasValue)
+                {
+                    var value = _template.Substring(_mark.Value, _index - _mark.Value);
+                    _mark = null;
+                    return value;
+                }
+                else
+                {
+                    return null;
+                }
+            }
+
+            private string DebuggerToString()
+            {
+                if (_index == -1)
+                {
+                    return _template;
+                }
+                else if (_mark.HasValue)
+                {
+                    return _template.Substring(0, _mark.Value) +
+                        "|" +
+                        _template.Substring(_mark.Value, _index - _mark.Value) +
+                        "|" +
+                        _template.Substring(_index);
+                }
+                else
+                {
+                    return _template.Substring(0, _index) + "|" + _template.Substring(_index);
+                }
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternPart.cs

@@ -0,0 +1,27 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    public abstract class RoutePatternPart
+    {
+        // This class is **not** an extensibility point - every part of the routing system
+        // needs to be aware of what kind of parts we support.
+        //
+        // It is abstract so we can add semantics later inside the library.
+        private protected RoutePatternPart(RoutePatternPartKind partKind)
+        {
+            PartKind = partKind;
+        }
+
+        public RoutePatternPartKind PartKind { get; }
+
+        public bool IsLiteral => PartKind == RoutePatternPartKind.Literal;
+
+        public bool IsParameter => PartKind == RoutePatternPartKind.Parameter;
+
+        public bool IsSeparator => PartKind == RoutePatternPartKind.Separator;
+
+        internal abstract string DebuggerToString();
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternPartKind.cs

@@ -0,0 +1,12 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    public enum RoutePatternPartKind
+    {
+        Literal,
+        Parameter,
+        Separator,
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternPathSegment.cs

@@ -0,0 +1,32 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    [DebuggerDisplay("{DebuggerToString()}")]
+    public sealed class RoutePatternPathSegment
+    {
+        internal RoutePatternPathSegment(RoutePatternPart[] parts)
+        {
+            Parts = parts;
+        }
+
+        public bool IsSimple => Parts.Count == 1;
+
+        public IReadOnlyList<RoutePatternPart> Parts { get; }
+
+        internal string DebuggerToString()
+        {
+            return DebuggerToString(Parts);
+        }
+
+        internal static string DebuggerToString(IReadOnlyList<RoutePatternPart> parts)
+        {
+            return string.Join(string.Empty, parts.Select(p => p.DebuggerToString()));
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Patterns/RoutePatternSeparatorPart.cs

@@ -0,0 +1,26 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Diagnostics;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    [DebuggerDisplay("{DebuggerToString()}")]
+    public sealed class RoutePatternSeparatorPart : RoutePatternPart
+    {
+        internal RoutePatternSeparatorPart(string content)
+            : base(RoutePatternPartKind.Separator)
+        {
+            Debug.Assert(!string.IsNullOrEmpty(content));
+
+            Content = content;
+        }
+
+        public string Content { get; }
+
+        internal override string DebuggerToString()
+        {
+            return Content;
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Properties/Resources.Designer.cs

@@ -416,6 +416,48 @@ namespace Microsoft.AspNetCore.Routing
         internal static string FormatAmbiguousEndpoints(object p0, object p1)
             => string.Format(CultureInfo.CurrentCulture, GetString("AmbiguousEndpoints"), p0, p1);
 
+        /// <summary>
+        /// Value cannot be null or empty.
+        /// </summary>
+        internal static string Argument_NullOrEmpty
+        {
+            get => GetString("Argument_NullOrEmpty");
+        }
+
+        /// <summary>
+        /// Value cannot be null or empty.
+        /// </summary>
+        internal static string FormatArgument_NullOrEmpty()
+            => GetString("Argument_NullOrEmpty");
+
+        /// <summary>
+        /// The collection cannot be empty.
+        /// </summary>
+        internal static string RoutePatternBuilder_CollectionCannotBeEmpty
+        {
+            get => GetString("RoutePatternBuilder_CollectionCannotBeEmpty");
+        }
+
+        /// <summary>
+        /// The collection cannot be empty.
+        /// </summary>
+        internal static string FormatRoutePatternBuilder_CollectionCannotBeEmpty()
+            => GetString("RoutePatternBuilder_CollectionCannotBeEmpty");
+
+        /// <summary>
+        /// The constraint entry '{0}' - '{1}' must have a string value or be of a type which implements '{2}'.
+        /// </summary>
+        internal static string ConstraintMustBeStringOrConstraint
+        {
+            get => GetString("ConstraintMustBeStringOrConstraint");
+        }
+
+        /// <summary>
+        /// The constraint entry '{0}' - '{1}' must have a string value or be of a type which implements '{2}'.
+        /// </summary>
+        internal static string FormatConstraintMustBeStringOrConstraint(object p0, object p1, object p2)
+            => string.Format(CultureInfo.CurrentCulture, GetString("ConstraintMustBeStringOrConstraint"), p0, p1, p2);
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

src/Microsoft.AspNetCore.Routing/Resources.resx

@@ -204,4 +204,13 @@
   <data name="AmbiguousEndpoints" xml:space="preserve">
     <value>The request matched multiple endpoints. Matches: {0}{0}{1}</value>
   </data>
+  <data name="Argument_NullOrEmpty" xml:space="preserve">
+    <value>Value cannot be null or empty.</value>
+  </data>
+  <data name="RoutePatternBuilder_CollectionCannotBeEmpty" xml:space="preserve">
+    <value>The collection cannot be empty.</value>
+  </data>
+  <data name="ConstraintMustBeStringOrConstraint" xml:space="preserve">
+    <value>The constraint entry '{0}' - '{1}' must have a string value or be of a type which implements '{2}'.</value>
+  </data>
 </root>

src/Microsoft.AspNetCore.Routing/RouteCollection.cs

@@ -161,7 +161,7 @@ namespace Microsoft.AspNetCore.Routing
                     queryString = queryString.ToLowerInvariant();
                 }
 
-                if (_options.AppendTrailingSlash && !urlWithoutQueryString.EndsWith("/"))
+                if (_options.AppendTrailingSlash && !urlWithoutQueryString.EndsWith("/", StringComparison.Ordinal))
                 {
                     urlWithoutQueryString += "/";
                 }

src/Microsoft.AspNetCore.Routing/Template/InlineConstraint.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using Microsoft.AspNetCore.Routing.Patterns;
 
 namespace Microsoft.AspNetCore.Routing.Template
 {
@@ -24,6 +25,16 @@ namespace Microsoft.AspNetCore.Routing.Template
             Constraint = constraint;
         }
 
+        public InlineConstraint(RoutePatternConstraintReference other)
+        {
+            if (other == null)
+            {
+                throw new ArgumentNullException(nameof(other));
+            }
+
+            Constraint = other.Content;
+        }
+
         /// <summary>
         /// Gets the constraint text.
         /// </summary>

src/Microsoft.AspNetCore.Routing/Template/RouteTemplate.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using Microsoft.AspNetCore.Routing.Patterns;
 
 namespace Microsoft.AspNetCore.Routing.Template
 {
@@ -13,6 +14,25 @@ namespace Microsoft.AspNetCore.Routing.Template
     {
         private const string SeparatorString = "/";
 
+        public RouteTemplate(RoutePattern other)
+        {
+            TemplateText = other.RawText;
+            Segments = new List<TemplateSegment>(other.PathSegments.Select(p => new TemplateSegment(p)));
+            Parameters = new List<TemplatePart>();
+            for (var i = 0; i < Segments.Count; i++)
+            {
+                var segment = Segments[i];
+                for (var j = 0; j < segment.Parts.Count; j++)
+                {
+                    var part = segment.Parts[j];
+                    if (part.IsParameter)
+                    {
+                        Parameters.Add(part);
+                    }
+                }
+            }
+        }
+
         public RouteTemplate(string template, List<TemplateSegment> segments)
         {
             if (segments == null)
@@ -78,5 +98,16 @@ namespace Microsoft.AspNetCore.Routing.Template
 
             return null;
         }
+
+        /// <summary>
+        /// Converts the <see cref="RouteTemplate"/> to the equivalent 
+        /// <see cref="RoutePattern"/>
+        /// </summary>
+        /// <returns>A <see cref="RoutePattern"/>.</returns>
+        public RoutePattern ToRoutePattern()
+        {
+            var segments = Segments.Select(s => s.ToRoutePatternPathSegment());
+            return RoutePatternFactory.Pattern(TemplateText, segments);
+        }
     }
 }

src/Microsoft.AspNetCore.Routing/Template/TemplateMatcher.cs

@@ -2,10 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
-using System.Diagnostics;
+using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.Routing.Internal;
 
 namespace Microsoft.AspNetCore.Routing.Template
 {
@@ -19,6 +17,7 @@ namespace Microsoft.AspNetCore.Routing.Template
         private readonly object[] _defaultValues;
 
         private static readonly char[] Delimiters = new char[] { SeparatorChar };
+        private RoutePatternMatcher _routePatternMatcher;
 
         public TemplateMatcher(
             RouteTemplate template,
@@ -57,6 +56,9 @@ namespace Microsoft.AspNetCore.Routing.Template
                     _defaultValues[i] = value;
                 }
             }
+
+            var routePattern = Template.ToRoutePattern();
+            _routePatternMatcher = new RoutePatternMatcher(routePattern, Defaults);
         }
 
         public RouteValueDictionary Defaults { get; }
@@ -70,387 +72,7 @@ namespace Microsoft.AspNetCore.Routing.Template
                 throw new ArgumentNullException(nameof(values));
             }
 
-            var i = 0;
-            var pathTokenizer = new PathTokenizer(path);
-
-            // Perf: We do a traversal of the request-segments + route-segments twice.
-            //
-            // For most segment-types, we only really need to any work on one of the two passes.
-            //
-            // On the first pass, we're just looking to see if there's anything that would disqualify us from matching.
-            // The most common case would be a literal segment that doesn't match.
-            //
-            // On the second pass, we're almost certainly going to match the URL, so go ahead and allocate the 'values'
-            // and start capturing strings. 
-            foreach (var pathSegment in pathTokenizer)
-            {
-                if (pathSegment.Length == 0)
-                {
-                    return false;
-                }
-
-                var routeSegment = Template.GetSegment(i++);
-                if (routeSegment == null && pathSegment.Length > 0)
-                {
-                    // If routeSegment is null, then we're out of route segments. All we can match is the empty
-                    // string.
-                    return false;
-                }
-                else if (routeSegment.IsSimple && routeSegment.Parts[0].IsLiteral)
-                {
-                    // This is a literal segment, so we need to match the text, or the route isn't a match.
-                    var part = routeSegment.Parts[0];
-                    if (!pathSegment.Equals(part.Text, StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-                }
-                else if (routeSegment.IsSimple && routeSegment.Parts[0].IsCatchAll)
-                {
-                    // Nothing to validate for a catch-all - it can match any string, including the empty string.
-                    //
-                    // Also, a catch-all has to be the last part, so we're done.
-                    break;
-                }
-                else if (routeSegment.IsSimple && routeSegment.Parts[0].IsParameter)
-                {
-                    // For a parameter, validate that it's a has some length, or we have a default, or it's optional.
-                    var part = routeSegment.Parts[0];
-                    if (pathSegment.Length == 0 &&
-                        !_hasDefaultValue[i] &&
-                        !part.IsOptional)
-                    {
-                        // There's no value for this parameter, the route can't match.
-                        return false;
-                    }
-                }
-                else
-                {
-                    Debug.Assert(!routeSegment.IsSimple);
-
-                    // Don't attempt to validate a complex segment at this point other than being non-emtpy,
-                    // do it in the second pass.
-                }
-            }
-
-            for (; i < Template.Segments.Count; i++)
-            {
-                // We've matched the request path so far, but still have remaining route segments. These need
-                // to be all single-part parameter segments with default values or else they won't match.
-                var routeSegment = Template.GetSegment(i);
-                Debug.Assert(routeSegment != null);
-
-                if (!routeSegment.IsSimple)
-                {
-                    // If the segment is a complex segment, it MUST contain literals, and we've parsed the full
-                    // path so far, so it can't match.
-                    return false;
-                }
-
-                var part = routeSegment.Parts[0];
-                if (part.IsLiteral)
-                {
-                    // If the segment is a simple literal - which need the URL to provide a value, so we don't match.
-                    return false;
-                }
-
-                if (part.IsCatchAll)
-                {
-                    // Nothing to validate for a catch-all - it can match any string, including the empty string.
-                    //
-                    // Also, a catch-all has to be the last part, so we're done.
-                    break;
-                }
-
-                // If we get here, this is a simple segment with a parameter. We need it to be optional, or for the
-                // defaults to have a value.
-                Debug.Assert(routeSegment.IsSimple && part.IsParameter);
-                if (!_hasDefaultValue[i] && !part.IsOptional)
-                {
-                    // There's no default for this (non-optional) parameter so it can't match.
-                    return false;
-                }
-            }
-
-            // At this point we've very likely got a match, so start capturing values for real.
-
-            i = 0;
-            foreach (var requestSegment in pathTokenizer)
-            {
-                var routeSegment = Template.GetSegment(i++);
-
-                if (routeSegment.IsSimple && routeSegment.Parts[0].IsCatchAll)
-                {
-                    // A catch-all captures til the end of the string.
-                    var part = routeSegment.Parts[0];
-                    var captured = requestSegment.Buffer.Substring(requestSegment.Offset);
-                    if (captured.Length > 0)
-                    {
-                        values[part.Name] = captured;
-                    }
-                    else
-                    {
-                        // It's ok for a catch-all to produce a null value, so we don't check _hasDefaultValue.
-                        values[part.Name] = _defaultValues[i];
-                    }
-
-                    // A catch-all has to be the last part, so we're done.
-                    break;
-                }
-                else if (routeSegment.IsSimple && routeSegment.Parts[0].IsParameter)
-                {
-                    // A simple parameter captures the whole segment, or a default value if nothing was
-                    // provided.
-                    var part = routeSegment.Parts[0];
-                    if (requestSegment.Length > 0)
-                    {
-                        values[part.Name] = requestSegment.ToString();
-                    }
-                    else
-                    {
-                        if (_hasDefaultValue[i])
-                        {
-                            values[part.Name] = _defaultValues[i];
-                        }
-                    }
-                }
-                else if (!routeSegment.IsSimple)
-                {
-                    if (!MatchComplexSegment(routeSegment, requestSegment.ToString(), Defaults, values))
-                    {
-                        return false;
-                    }
-                }
-            }
-
-            for (; i < Template.Segments.Count; i++)
-            {
-                // We've matched the request path so far, but still have remaining route segments. We already know these
-                // are simple parameters that either have a default, or don't need to produce a value.
-                var routeSegment = Template.GetSegment(i);
-                Debug.Assert(routeSegment != null);
-                Debug.Assert(routeSegment.IsSimple);
-
-                var part = routeSegment.Parts[0];
-                Debug.Assert(part.IsParameter);
-
-                // It's ok for a catch-all to produce a null value
-                if (_hasDefaultValue[i] || part.IsCatchAll)
-                {
-                    // Don't replace an existing value with a null.
-                    var defaultValue = _defaultValues[i];
-                    if (defaultValue != null || !values.ContainsKey(part.Name))
-                    {
-                        values[part.Name] = defaultValue;
-                    }
-                }
-            }
-
-            // Copy all remaining default values to the route data
-            foreach (var kvp in Defaults)
-            {
-                if (!values.ContainsKey(kvp.Key))
-                {
-                    values.Add(kvp.Key, kvp.Value);
-                }
-            }
-
-            return true;
-        }
-
-        private bool MatchComplexSegment(
-            TemplateSegment routeSegment,
-            string requestSegment,
-            IReadOnlyDictionary<string, object> defaults,
-            RouteValueDictionary values)
-        {
-            var indexOfLastSegment = routeSegment.Parts.Count - 1;
-
-            // We match the request to the template starting at the rightmost parameter
-            // If the last segment of template is optional, then request can match the 
-            // template with or without the last parameter. So we start with regular matching,
-            // but if it doesn't match, we start with next to last parameter. Example:
-            // Template: {p1}/{p2}.{p3?}. If the request is one/two.three it will match right away
-            // giving p3 value of three. But if the request is one/two, we start matching from the
-            // rightmost giving p3 the value of two, then we end up not matching the segment.
-            // In this case we start again from p2 to match the request and we succeed giving
-            // the value two to p2
-            if (routeSegment.Parts[indexOfLastSegment].IsOptional &&
-                routeSegment.Parts[indexOfLastSegment - 1].IsOptionalSeperator)
-            {
-                if (MatchComplexSegmentCore(routeSegment, requestSegment, Defaults, values, indexOfLastSegment))
-                {
-                    return true;
-                }
-                else
-                {
-                    if (requestSegment.EndsWith(
-                        routeSegment.Parts[indexOfLastSegment - 1].Text,
-                        StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-
-                    return MatchComplexSegmentCore(
-                        routeSegment,
-                        requestSegment,
-                        Defaults,
-                        values,
-                        indexOfLastSegment - 2);
-                }
-            }
-            else
-            {
-                return MatchComplexSegmentCore(routeSegment, requestSegment, Defaults, values, indexOfLastSegment);
-            }
-        }
-
-        private bool MatchComplexSegmentCore(
-            TemplateSegment routeSegment,
-            string requestSegment,
-            IReadOnlyDictionary<string, object> defaults,
-            RouteValueDictionary values,
-            int indexOfLastSegmentUsed)
-        {
-            Debug.Assert(routeSegment != null);
-            Debug.Assert(routeSegment.Parts.Count > 1);
-
-            // Find last literal segment and get its last index in the string
-            var lastIndex = requestSegment.Length;
-
-            TemplatePart parameterNeedsValue = null; // Keeps track of a parameter segment that is pending a value
-            TemplatePart lastLiteral = null; // Keeps track of the left-most literal we've encountered
-
-            var outValues = new RouteValueDictionary();
-
-            while (indexOfLastSegmentUsed >= 0)
-            {
-                var newLastIndex = lastIndex;
-
-                var part = routeSegment.Parts[indexOfLastSegmentUsed];
-                if (part.IsParameter)
-                {
-                    // Hold on to the parameter so that we can fill it in when we locate the next literal
-                    parameterNeedsValue = part;
-                }
-                else
-                {
-                    Debug.Assert(part.IsLiteral);
-                    lastLiteral = part;
-
-                    var startIndex = lastIndex - 1;
-                    // If we have a pending parameter subsegment, we must leave at least one character for that
-                    if (parameterNeedsValue != null)
-                    {
-                        startIndex--;
-                    }
-
-                    if (startIndex < 0)
-                    {
-                        return false;
-                    }
-
-                    var indexOfLiteral = requestSegment.LastIndexOf(
-                        part.Text,
-                        startIndex,
-                        StringComparison.OrdinalIgnoreCase);
-                    if (indexOfLiteral == -1)
-                    {
-                        // If we couldn't find this literal index, this segment cannot match
-                        return false;
-                    }
-
-                    // If the first subsegment is a literal, it must match at the right-most extent of the request URI.
-                    // Without this check if your route had "/Foo/" we'd match the request URI "/somethingFoo/".
-                    // This check is related to the check we do at the very end of this function.
-                    if (indexOfLastSegmentUsed == (routeSegment.Parts.Count - 1))
-                    {
-                        if ((indexOfLiteral + part.Text.Length) != requestSegment.Length)
-                        {
-                            return false;
-                        }
-                    }
-
-                    newLastIndex = indexOfLiteral;
-                }
-
-                if ((parameterNeedsValue != null) &&
-                    (((lastLiteral != null) && (part.IsLiteral)) || (indexOfLastSegmentUsed == 0)))
-                {
-                    // If we have a pending parameter that needs a value, grab that value
-
-                    int parameterStartIndex;
-                    int parameterTextLength;
-
-                    if (lastLiteral == null)
-                    {
-                        if (indexOfLastSegmentUsed == 0)
-                        {
-                            parameterStartIndex = 0;
-                        }
-                        else
-                        {
-                            parameterStartIndex = newLastIndex;
-                            Debug.Assert(false, "indexOfLastSegementUsed should always be 0 from the check above");
-                        }
-                        parameterTextLength = lastIndex;
-                    }
-                    else
-                    {
-                        // If we're getting a value for a parameter that is somewhere in the middle of the segment
-                        if ((indexOfLastSegmentUsed == 0) && (part.IsParameter))
-                        {
-                            parameterStartIndex = 0;
-                            parameterTextLength = lastIndex;
-                        }
-                        else
-                        {
-                            parameterStartIndex = newLastIndex + lastLiteral.Text.Length;
-                            parameterTextLength = lastIndex - parameterStartIndex;
-                        }
-                    }
-
-                    var parameterValueString = requestSegment.Substring(parameterStartIndex, parameterTextLength);
-
-                    if (string.IsNullOrEmpty(parameterValueString))
-                    {
-                        // If we're here that means we have a segment that contains multiple sub-segments.
-                        // For these segments all parameters must have non-empty values. If the parameter
-                        // has an empty value it's not a match.                        
-                        return false;
-
-                    }
-                    else
-                    {
-                        // If there's a value in the segment for this parameter, use the subsegment value
-                        outValues.Add(parameterNeedsValue.Name, parameterValueString);
-                    }
-
-                    parameterNeedsValue = null;
-                    lastLiteral = null;
-                }
-
-                lastIndex = newLastIndex;
-                indexOfLastSegmentUsed--;
-            }
-
-            // If the last subsegment is a parameter, it's OK that we didn't parse all the way to the left extent of
-            // the string since the parameter will have consumed all the remaining text anyway. If the last subsegment
-            // is a literal then we *must* have consumed the entire text in that literal. Otherwise we end up matching
-            // the route "Foo" to the request URI "somethingFoo". Thus we have to check that we parsed the *entire*
-            // request URI in order for it to be a match.
-            // This check is related to the check we do earlier in this function for LiteralSubsegments.
-            if (lastIndex == 0 || routeSegment.Parts[0].IsParameter)
-            {
-                foreach (var item in outValues)
-                {
-                    values.Add(item.Key, item.Value);
-                }
-
-                return true;
-            }
-
-            return false;
+            return _routePatternMatcher.TryMatch(path, values);
         }
     }
 }

src/Microsoft.AspNetCore.Routing/Template/TemplateParser.cs

@@ -1,539 +1,29 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
-using System.Diagnostics;
-using System.Globalization;
+using Microsoft.AspNetCore.Routing.Patterns;
 
 namespace Microsoft.AspNetCore.Routing.Template
 {
     public static class TemplateParser
     {
-        private const char Separator = '/';
-        private const char OpenBrace = '{';
-        private const char CloseBrace = '}';
-        private const char EqualsSign = '=';
-        private const char QuestionMark = '?';
-        private const char Asterisk = '*';
-        private const string PeriodString = ".";
-
         public static RouteTemplate Parse(string routeTemplate)
         {
             if (routeTemplate == null)
             {
-                routeTemplate = String.Empty;
+                throw new ArgumentNullException(routeTemplate);
             }
 
-            var trimmedRouteTemplate = TrimPrefix(routeTemplate);
-
-            var context = new TemplateParserContext(trimmedRouteTemplate);
-            var segments = new List<TemplateSegment>();
-
-            while (context.Next())
+            try
             {
-                if (context.Current == Separator)
-                {
-                    // If we get here is means that there's a consecutive '/' character.
-                    // Templates don't start with a '/' and parsing a segment consumes the separator.
-                    throw new ArgumentException(Resources.TemplateRoute_CannotHaveConsecutiveSeparators,
-                                                nameof(routeTemplate));
-                }
-                else
-                {
-                    if (!ParseSegment(context, segments))
-                    {
-                        throw new ArgumentException(context.Error, nameof(routeTemplate));
-                    }
-                }
+                var inner = RoutePatternFactory.Parse(routeTemplate);
+                return new RouteTemplate(inner);
             }
-
-            if (IsAllValid(context, segments))
+            catch (RoutePatternException ex)
             {
-                return new RouteTemplate(routeTemplate, segments);
-            }
-            else
-            {
-                throw new ArgumentException(context.Error, nameof(routeTemplate));
-            }
-        }
-
-        private static string TrimPrefix(string routeTemplate)
-        {
-            if (routeTemplate.StartsWith("~/", StringComparison.Ordinal))
-            {
-                return routeTemplate.Substring(2);
-            }
-            else if (routeTemplate.StartsWith("/", StringComparison.Ordinal))
-            {
-                return routeTemplate.Substring(1);
-            }
-            else if (routeTemplate.StartsWith("~", StringComparison.Ordinal))
-            {
-                throw new ArgumentException(Resources.TemplateRoute_InvalidRouteTemplate, nameof(routeTemplate));
-            }
-            return routeTemplate;
-        }
-
-        private static bool ParseSegment(TemplateParserContext context, List<TemplateSegment> segments)
-        {
-            Debug.Assert(context != null);
-            Debug.Assert(segments != null);
-
-            var segment = new TemplateSegment();
-
-            while (true)
-            {
-                if (context.Current == OpenBrace)
-                {
-                    if (!context.Next())
-                    {
-                        // This is a dangling open-brace, which is not allowed
-                        context.Error = Resources.TemplateRoute_MismatchedParameter;
-                        return false;
-                    }
-
-                    if (context.Current == OpenBrace)
-                    {
-                        // This is an 'escaped' brace in a literal, like "{{foo"
-                        context.Back();
-                        if (!ParseLiteral(context, segment))
-                        {
-                            return false;
-                        }
-                    }
-                    else
-                    {
-                        // This is the inside of a parameter
-                        if (!ParseParameter(context, segment))
-                        {
-                            return false;
-                        }
-                    }
-                }
-                else if (context.Current == Separator)
-                {
-                    // We've reached the end of the segment
-                    break;
-                }
-                else
-                {
-                    if (!ParseLiteral(context, segment))
-                    {
-                        return false;
-                    }
-                }
-
-                if (!context.Next())
-                {
-                    // We've reached the end of the string
-                    break;
-                }
-            }
-
-            if (IsSegmentValid(context, segment))
-            {
-                segments.Add(segment);
-                return true;
-            }
-            else
-            {
-                return false;
-            }
-        }
-
-        private static bool ParseParameter(TemplateParserContext context, TemplateSegment segment)
-        {
-            context.Mark();
-
-            while (true)
-            {
-                if (context.Current == OpenBrace)
-                {
-                    // This is an open brace inside of a parameter, it has to be escaped
-                    if (context.Next())
-                    {
-                        if (context.Current != OpenBrace)
-                        {
-                            // If we see something like "{p1:regex(^\d{3", we will come here.
-                            context.Error = Resources.TemplateRoute_UnescapedBrace;
-                            return false;
-                        }
-                    }
-                    else
-                    {
-                        // This is a dangling open-brace, which is not allowed
-                        // Example: "{p1:regex(^\d{"
-                        context.Error = Resources.TemplateRoute_MismatchedParameter;
-                        return false;
-                    }
-                }
-                else if (context.Current == CloseBrace)
-                {
-                    // When we encounter Closed brace here, it either means end of the parameter or it is a closed 
-                    // brace in the parameter, in that case it needs to be escaped.
-                    // Example: {p1:regex(([}}])\w+}. First pair is escaped one and last marks end of the parameter
-                    if (!context.Next())
-                    {
-                        // This is the end of the string -and we have a valid parameter
-                        context.Back();
-                        break;
-                    }
-
-                    if (context.Current == CloseBrace)
-                    {
-                        // This is an 'escaped' brace in a parameter name
-                    }
-                    else
-                    {
-                        // This is the end of the parameter
-                        context.Back();
-                        break;
-                    }
-                }
-
-                if (!context.Next())
-                {
-                    // This is a dangling open-brace, which is not allowed
-                    context.Error = Resources.TemplateRoute_MismatchedParameter;
-                    return false;
-                }
-            }
-
-            var rawParameter = context.Capture();
-            var decoded = rawParameter.Replace("}}", "}").Replace("{{", "{");
-
-            // At this point, we need to parse the raw name for inline constraint,
-            // default values and optional parameters.
-            var templatePart = InlineRouteParameterParser.ParseRouteParameter(decoded);
-
-            if (templatePart.IsCatchAll && templatePart.IsOptional)
-            {
-                context.Error = Resources.TemplateRoute_CatchAllCannotBeOptional;
-                return false;
-            }
-
-            if (templatePart.IsOptional && templatePart.DefaultValue != null)
-            {
-                // Cannot be optional and have a default value.
-                // The only way to declare an optional parameter is to have a ? at the end,
-                // hence we cannot have both default value and optional parameter within the template.
-                // A workaround is to add it as a separate entry in the defaults argument.
-                context.Error = Resources.TemplateRoute_OptionalCannotHaveDefaultValue;
-                return false;
-            }
-
-            var parameterName = templatePart.Name;
-            if (IsValidParameterName(context, parameterName))
-            {
-                segment.Parts.Add(templatePart);
-                return true;
-            }
-            else
-            {
-                return false;
-            }
-        }
-
-        private static bool ParseLiteral(TemplateParserContext context, TemplateSegment segment)
-        {
-            context.Mark();
-
-            string encoded;
-            while (true)
-            {
-                if (context.Current == Separator)
-                {
-                    encoded = context.Capture();
-                    context.Back();
-                    break;
-                }
-                else if (context.Current == OpenBrace)
-                {
-                    if (!context.Next())
-                    {
-                        // This is a dangling open-brace, which is not allowed
-                        context.Error = Resources.TemplateRoute_MismatchedParameter;
-                        return false;
-                    }
-
-                    if (context.Current == OpenBrace)
-                    {
-                        // This is an 'escaped' brace in a literal, like "{{foo" - keep going.
-                    }
-                    else
-                    {
-                        // We've just seen the start of a parameter, so back up and return
-                        context.Back();
-                        encoded = context.Capture();
-                        context.Back();
-                        break;
-                    }
-                }
-                else if (context.Current == CloseBrace)
-                {
-                    if (!context.Next())
-                    {
-                        // This is a dangling close-brace, which is not allowed
-                        context.Error = Resources.TemplateRoute_MismatchedParameter;
-                        return false;
-                    }
-
-                    if (context.Current == CloseBrace)
-                    {
-                        // This is an 'escaped' brace in a literal, like "{{foo" - keep going.
-                    }
-                    else
-                    {
-                        // This is an unbalanced close-brace, which is not allowed
-                        context.Error = Resources.TemplateRoute_MismatchedParameter;
-                        return false;
-                    }
-                }
-
-                if (!context.Next())
-                {
-                    encoded = context.Capture();
-                    break;
-                }
-            }
-
-            var decoded = encoded.Replace("}}", "}").Replace("{{", "{");
-            if (IsValidLiteral(context, decoded))
-            {
-                segment.Parts.Add(TemplatePart.CreateLiteral(decoded));
-                return true;
-            }
-            else
-            {
-                return false;
-            }
-        }
-
-        private static bool IsAllValid(TemplateParserContext context, List<TemplateSegment> segments)
-        {
-            // A catch-all parameter must be the last part of the last segment
-            for (var i = 0; i < segments.Count; i++)
-            {
-                var segment = segments[i];
-                for (var j = 0; j < segment.Parts.Count; j++)
-                {
-                    var part = segment.Parts[j];
-                    if (part.IsParameter &&
-                        part.IsCatchAll &&
-                        (i != segments.Count - 1 || j != segment.Parts.Count - 1))
-                    {
-                        context.Error = Resources.TemplateRoute_CatchAllMustBeLast;
-                        return false;
-                    }
-                }
-            }
-
-            return true;
-        }
-
-        private static bool IsSegmentValid(TemplateParserContext context, TemplateSegment segment)
-        {
-            // If a segment has multiple parts, then it can't contain a catch all.
-            for (var i = 0; i < segment.Parts.Count; i++)
-            {
-                var part = segment.Parts[i];
-                if (part.IsParameter && part.IsCatchAll && segment.Parts.Count > 1)
-                {
-                    context.Error = Resources.TemplateRoute_CannotHaveCatchAllInMultiSegment;
-                    return false;
-                }
-            }
-
-            // if a segment has multiple parts, then only the last one parameter can be optional 
-            // if it is following a optional seperator. 
-            for (var i = 0; i < segment.Parts.Count; i++)
-            {
-                var part = segment.Parts[i];
-
-                if (part.IsParameter && part.IsOptional && segment.Parts.Count > 1)
-                {
-                    // This optional parameter is the last part in the segment
-                    if (i == segment.Parts.Count - 1)
-                    {
-                        if (!segment.Parts[i - 1].IsLiteral)
-                        {
-                            // The optional parameter is preceded by something that is not a literal.
-                            // Example of error message:
-                            // "In the segment '{RouteValue}{param?}', the optional parameter 'param' is preceded
-                            // by an invalid segment '{RouteValue}'. Only a period (.) can precede an optional parameter.
-                            context.Error = string.Format(
-                                Resources.TemplateRoute_OptionalParameterCanbBePrecededByPeriod,
-                                segment.DebuggerToString(),
-                                part.Name,
-                                segment.Parts[i - 1].DebuggerToString());
-
-                            return false;
-                        }
-                        else if (segment.Parts[i - 1].Text != PeriodString)
-                        {
-                            // The optional parameter is preceded by a literal other than period.
-                            // Example of error message:
-                            // "In the segment '{RouteValue}-{param?}', the optional parameter 'param' is preceded
-                            // by an invalid segment '-'. Only a period (.) can precede an optional parameter.
-                            context.Error = string.Format(
-                                Resources.TemplateRoute_OptionalParameterCanbBePrecededByPeriod,
-                                segment.DebuggerToString(),
-                                part.Name,
-                                segment.Parts[i - 1].Text);
-
-                            return false;
-                        }
-
-                        segment.Parts[i - 1].IsOptionalSeperator = true;
-                    }
-                    else
-                    {
-                        // This optional parameter is not the last one in the segment
-                        // Example:
-                        // An optional parameter must be at the end of the segment.In the segment '{RouteValue?})', 
-                        // optional parameter 'RouteValue' is followed by ')'
-                        var nextPart = segment.Parts[i + 1];
-                        var invalidPartText = nextPart.IsParameter ? nextPart.Name : nextPart.Text;
-
-                        context.Error = string.Format(
-                            Resources.TemplateRoute_OptionalParameterHasTobeTheLast,
-                            segment.DebuggerToString(),
-                            segment.Parts[i].Name,
-                            invalidPartText);
-
-                        return false;
-                    }
-                }
-            }
-
-            // A segment cannot contain two consecutive parameters
-            var isLastSegmentParameter = false;
-            for (var i = 0; i < segment.Parts.Count; i++)
-            {
-                var part = segment.Parts[i];
-                if (part.IsParameter && isLastSegmentParameter)
-                {
-                    context.Error = Resources.TemplateRoute_CannotHaveConsecutiveParameters;
-                    return false;
-                }
-
-                isLastSegmentParameter = part.IsParameter;
-            }
-
-            return true;
-        }
-
-        private static bool IsValidParameterName(TemplateParserContext context, string parameterName)
-        {
-            if (parameterName.Length == 0)
-            {
-                context.Error = String.Format(CultureInfo.CurrentCulture,
-                                              Resources.TemplateRoute_InvalidParameterName, parameterName);
-                return false;
-            }
-
-            for (var i = 0; i < parameterName.Length; i++)
-            {
-                var c = parameterName[i];
-                if (c == Separator || c == OpenBrace || c == CloseBrace || c == QuestionMark || c == Asterisk)
-                {
-                    context.Error = String.Format(CultureInfo.CurrentCulture,
-                                                  Resources.TemplateRoute_InvalidParameterName, parameterName);
-                    return false;
-                }
-            }
-
-            if (!context.ParameterNames.Add(parameterName))
-            {
-                context.Error = String.Format(CultureInfo.CurrentCulture,
-                                              Resources.TemplateRoute_RepeatedParameter, parameterName);
-                return false;
-            }
-
-            return true;
-        }
-
-        private static bool IsValidLiteral(TemplateParserContext context, string literal)
-        {
-            Debug.Assert(context != null);
-            Debug.Assert(literal != null);
-
-            if (literal.IndexOf(QuestionMark) != -1)
-            {
-                context.Error = String.Format(CultureInfo.CurrentCulture,
-                                              Resources.TemplateRoute_InvalidLiteral, literal);
-                return false;
-            }
-
-            return true;
-        }
-
-        private static bool IsInvalidRouteTemplate(string routeTemplate)
-        {
-            return routeTemplate.StartsWith("~", StringComparison.Ordinal) ||
-                   routeTemplate.StartsWith("/", StringComparison.Ordinal);
-        }
-
-        private class TemplateParserContext
-        {
-            private readonly string _template;
-            private int _index;
-            private int? _mark;
-
-            private HashSet<string> _parameterNames = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
-
-            public TemplateParserContext(string template)
-            {
-                Debug.Assert(template != null);
-                _template = template;
-
-                _index = -1;
-            }
-
-            public char Current
-            {
-                get { return (_index < _template.Length && _index >= 0) ? _template[_index] : (char)0; }
-            }
-
-            public string Error
-            {
-                get;
-                set;
-            }
-
-            public HashSet<string> ParameterNames
-            {
-                get { return _parameterNames; }
-            }
-
-            public bool Back()
-            {
-                return --_index >= 0;
-            }
-
-            public bool Next()
-            {
-                return ++_index < _template.Length;
-            }
-
-            public void Mark()
-            {
-                _mark = _index;
-            }
-
-            public string Capture()
-            {
-                if (_mark.HasValue)
-                {
-                    var value = _template.Substring(_mark.Value, _index - _mark.Value);
-                    _mark = null;
-                    return value;
-                }
-                else
-                {
-                    return null;
-                }
+                // Preserving the existing behavior of this API even though the logic moved.
+                throw new ArgumentException(ex.Message, nameof(routeTemplate), ex);
             }
         }
     }

src/Microsoft.AspNetCore.Routing/Template/TemplatePart.cs

@@ -5,12 +5,47 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using Microsoft.AspNetCore.Routing.Patterns;
 
 namespace Microsoft.AspNetCore.Routing.Template
 {
     [DebuggerDisplay("{DebuggerToString()}")]
     public class TemplatePart
     {
+        public TemplatePart()
+        {
+        }
+
+        public TemplatePart(RoutePatternPart other)
+        {
+            IsLiteral = other.IsLiteral || other.IsSeparator;
+            IsParameter = other.IsParameter;
+
+            if (other.IsLiteral && other is RoutePatternLiteralPart literal)
+            {
+                Text = literal.Content;
+            }
+            else if (other.IsParameter && other is RoutePatternParameterPart parameter)
+            {
+                // Text is unused by TemplatePart and assumed to be null when the part is a parameter.
+                Name = parameter.Name;
+                IsCatchAll = parameter.IsCatchAll;
+                IsOptional = parameter.IsOptional;
+                DefaultValue = parameter.Default;
+                InlineConstraints = parameter.Constraints?.Select(p => new InlineConstraint(p));
+            }
+            else if (other.IsSeparator && other is RoutePatternSeparatorPart separator)
+            {
+                Text = separator.Content;
+                IsOptionalSeperator = true;
+            }
+            else
+            {
+                // Unreachable
+                throw new NotSupportedException();
+            }
+        }
+
         public static TemplatePart CreateLiteral(string text)
         {
             return new TemplatePart()
@@ -20,11 +55,12 @@ namespace Microsoft.AspNetCore.Routing.Template
             };
         }
 
-        public static TemplatePart CreateParameter(string name,
-                                                   bool isCatchAll,
-                                                   bool isOptional,
-                                                   object defaultValue,
-                                                   IEnumerable<InlineConstraint> inlineConstraints)
+        public static TemplatePart CreateParameter(
+            string name,
+            bool isCatchAll,
+            bool isOptional,
+            object defaultValue,
+            IEnumerable<InlineConstraint> inlineConstraints)
         {
             if (name == null)
             {
@@ -63,5 +99,28 @@ namespace Microsoft.AspNetCore.Routing.Template
                 return Text;
             }
         }
+
+        public RoutePatternPart ToRoutePatternPart()
+        {
+            if (IsLiteral && IsOptionalSeperator)
+            {
+                return RoutePatternFactory.SeparatorPart(Text);
+            }
+            else if (IsLiteral)
+            {
+                return RoutePatternFactory.LiteralPart(Text);
+            }
+            else
+            {
+                var kind = IsCatchAll ?
+                    RoutePatternParameterKind.CatchAll :
+                    IsOptional ?
+                        RoutePatternParameterKind.Optional :
+                        RoutePatternParameterKind.Standard;
+
+                var constraints = InlineConstraints.Select(c => new RoutePatternConstraintReference(Name, c.Constraint));
+                return RoutePatternFactory.ParameterPart(Name, DefaultValue, kind, constraints);
+            }
+        }
     }
 }

src/Microsoft.AspNetCore.Routing/Template/TemplateSegment.cs

@@ -4,19 +4,36 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using Microsoft.AspNetCore.Routing.Patterns;
 
 namespace Microsoft.AspNetCore.Routing.Template
 {
     [DebuggerDisplay("{DebuggerToString()}")]
     public class TemplateSegment
     {
+        public TemplateSegment()
+        {
+            Parts = new List<TemplatePart>();
+        }
+
+        public TemplateSegment(RoutePatternPathSegment other)
+        {
+            Parts = new List<TemplatePart>(other.Parts.Select(s => new TemplatePart(s)));
+        }
+
         public bool IsSimple => Parts.Count == 1;
 
-        public List<TemplatePart> Parts { get; } = new List<TemplatePart>();
+        public List<TemplatePart> Parts { get; }
 
         internal string DebuggerToString()
         {
             return string.Join(string.Empty, Parts.Select(p => p.DebuggerToString()));
         }
+
+        public RoutePatternPathSegment ToRoutePatternPathSegment()
+        {
+            var parts = Parts.Select(p => p.ToRoutePatternPart());
+            return RoutePatternFactory.Segment(parts);
+        }
     }
 }

test/Microsoft.AspNetCore.Routing.Tests/Patterns/InlineRouteParameterParserTest.cs

@@ -0,0 +1,946 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Linq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    public class InlineRouteParameterParserTest
+    {
+        [Theory]
+        [InlineData("=")]
+        [InlineData(":")]
+        public void ParseRouteParameter_WithoutADefaultValue(string parameterName)
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(parameterName);
+
+            // Assert
+            Assert.Equal(parameterName, templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.Empty(templatePart.Constraints);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_WithEmptyDefaultValue()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter("param=");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("", templatePart.Default);
+            Assert.Empty(templatePart.Constraints);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_WithoutAConstraintName()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter("param:");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.Empty(templatePart.Constraints);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_WithoutAConstraintNameOrParameterName()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter("param:=");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("", templatePart.Default);
+            Assert.Empty(templatePart.Constraints);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_WithADefaultValueContainingConstraintSeparator()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter("param=:");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal(":", templatePart.Default);
+            Assert.Empty(templatePart.Constraints);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintAndDefault_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter("param:int=111111");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("111111", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("int", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithArgumentsAndDefault_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\d+)=111111");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("111111", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\d+)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintAndOptional_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:int?");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.True(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("int", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintAndOptional_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:int=12?");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("12", templatePart.Default);
+            Assert.True(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("int", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintAndOptional_WithDefaultValueWithQuestionMark_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:int=12??");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("12?", templatePart.Default);
+            Assert.True(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("int", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithArgumentsAndOptional_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\d+)?");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.True(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\d+)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithArgumentsAndOptional_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\d+)=abc?");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.True(templatePart.IsOptional);
+
+            Assert.Equal("abc", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\d+)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ChainedConstraints_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(d+):test(w+)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Collection(templatePart.Constraints,
+                constraint => Assert.Equal(@"test(d+)", constraint.Content),
+                constraint => Assert.Equal(@"test(w+)", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ChainedConstraints_DoubleDelimiters_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param::test(d+)::test(w+)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Collection(
+                templatePart.Constraints,
+                constraint => Assert.Equal(@"test(d+)", constraint.Content),
+                constraint => Assert.Equal(@"test(w+)", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ChainedConstraints_ColonInPattern_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\d+):test(\w:+)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Collection(templatePart.Constraints,
+                constraint => Assert.Equal(@"test(\d+)", constraint.Content),
+                constraint => Assert.Equal(@"test(\w:+)", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ChainedConstraints_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\d+):test(\w+)=qwer");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Equal("qwer", templatePart.Default);
+
+            Assert.Collection(templatePart.Constraints,
+                constraint => Assert.Equal(@"test(\d+)", constraint.Content),
+                constraint => Assert.Equal(@"test(\w+)", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ChainedConstraints_WithDefaultValue_DoubleDelimiters_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\d+)::test(\w+)==qwer");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Equal("=qwer", templatePart.Default);
+
+            Assert.Collection(
+                templatePart.Constraints,
+                constraint => Assert.Equal(@"test(\d+)", constraint.Content),
+                constraint => Assert.Equal(@"test(\w+)", constraint.Content));
+        }
+
+        [Theory]
+        [InlineData("=")]
+        [InlineData("+=")]
+        [InlineData(">= || <= || ==")]
+        public void ParseRouteParameter_WithDefaultValue_ContainingDelimiter(string defaultValue)
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter($"comparison-operator:length(6)={defaultValue}");
+
+            // Assert
+            Assert.Equal("comparison-operator", templatePart.Name);
+            Assert.Equal(defaultValue, templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("length(6)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteTemplate_ConstraintsDefaultsAndOptionalsInMultipleSections_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var routePattern = RoutePatternFactory.Parse(@"some/url-{p1:int:test(3)=hello}/{p2=abc}/{p3?}");
+
+            // Assert
+            var parameters = routePattern.Parameters.ToArray();
+
+            var param1 = parameters[0];
+            Assert.Equal("p1", param1.Name);
+            Assert.Equal("hello", param1.Default);
+            Assert.False(param1.IsOptional);
+
+            Assert.Collection(param1.Constraints,
+                constraint => Assert.Equal("int", constraint.Content),
+                constraint => Assert.Equal("test(3)", constraint.Content)
+            );
+
+            var param2 = parameters[1];
+            Assert.Equal("p2", param2.Name);
+            Assert.Equal("abc", param2.Default);
+            Assert.False(param2.IsOptional);
+
+            var param3 = parameters[2];
+            Assert.Equal("p3", param3.Name);
+            Assert.True(param3.IsOptional);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_NoTokens_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter("world");
+
+            // Assert
+            Assert.Equal("world", templatePart.Name);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ParamDefault_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter("param=world");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("world", templatePart.Default);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithClosingBraceInPattern_ClosingBraceIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\})");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\})", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithClosingBraceInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\})=wer");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Equal("wer", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\})", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithClosingParenInPattern_ClosingParenIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\))");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\))", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithClosingParenInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\))=fsd");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Equal("fsd", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\))", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithColonInPattern_ColonIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(:)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(:)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithColonInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(:)=mnf");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Equal("mnf", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(:)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithColonsInPattern_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(a:b:c)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(a:b:c)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithColonInParamName_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@":param:test=12");
+
+            // Assert
+            Assert.Equal(":param", templatePart.Name);
+
+            Assert.Equal("12", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("test", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithTwoColonInParamName_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@":param::test=12");
+
+            // Assert
+            Assert.Equal(":param", templatePart.Name);
+
+            Assert.Equal("12", templatePart.Default);
+
+            Assert.Collection(
+                templatePart.Constraints,
+                constraint => Assert.Equal("test", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_EmptyConstraint_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@":param:test:");
+
+            // Assert
+            Assert.Equal(":param", templatePart.Name);
+
+            Assert.Collection(
+                templatePart.Constraints,
+                constraint => Assert.Equal("test", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithCommaInPattern_PatternIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\w,\w)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\w,\w)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithCommaInName_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"par,am:test(\w)");
+
+            // Assert
+            Assert.Equal("par,am", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\w)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithCommaInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\w,\w)=jsd");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Equal("jsd", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\w,\w)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithEqualsFollowedByQuestionMark_PatternIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:int=?");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("", templatePart.Default);
+
+            Assert.True(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("int", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithEqualsSignInPattern_PatternIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(=)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Null(templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("test(=)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_EqualsSignInDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param=test=bar");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("test=bar", templatePart.Default);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithEqualEqualSignInPattern_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(a==b)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Null(templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("test(a==b)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithEqualEqualSignInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(a==b)=dvds");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("dvds", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("test(a==b)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_EqualEqualSignInName_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"par==am:test=dvds");
+
+            // Assert
+            Assert.Equal("par", templatePart.Name);
+            Assert.Equal("=am:test=dvds", templatePart.Default);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_EqualEqualSignInDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test==dvds");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("=dvds", templatePart.Default);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_DefaultValueWithColonAndParens_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"par=am:test(asd)");
+
+            // Assert
+            Assert.Equal("par", templatePart.Name);
+            Assert.Equal("am:test(asd)", templatePart.Default);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_DefaultValueWithEqualsSignIn_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"par=test(am):est=asd");
+
+            // Assert
+            Assert.Equal("par", templatePart.Name);
+            Assert.Equal("test(am):est=asd", templatePart.Default);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithEqualsSignInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(=)=sds");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("sds", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("test(=)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenBraceInPattern_PatternIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\{)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\{)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenBraceInName_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"par{am:test(\sd)");
+
+            // Assert
+            Assert.Equal("par{am", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\sd)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenBraceInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\{)=xvc");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Equal("xvc", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\{)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenParenInName_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"par(am:test(\()");
+
+            // Assert
+            Assert.Equal("par(am", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\()", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenParenInPattern_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\()");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\()", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenParenNoCloseParen_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(#$%");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal("test(#$%", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenParenAndColon_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(#:test1");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Collection(templatePart.Constraints,
+                constraint => Assert.Equal(@"test(#", constraint.Content),
+                constraint => Assert.Equal(@"test1", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenParenAndColonWithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(abc:somevalue):name(test1:differentname=default-value");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("default-value", templatePart.Default);
+
+            Assert.Collection(templatePart.Constraints,
+                constraint => Assert.Equal(@"test(abc:somevalue)", constraint.Content),
+                constraint => Assert.Equal(@"name(test1", constraint.Content),
+                constraint => Assert.Equal(@"differentname", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenParenAndDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(constraintvalue=test1");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("test1", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(constraintvalue", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithOpenParenInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\()=djk");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+
+            Assert.Equal("djk", templatePart.Default);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\()", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithQuestionMarkInPattern_PatternIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\?)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.False(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\?)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithQuestionMarkInPattern_Optional_PatternIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\?)?");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.True(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\?)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithQuestionMarkInPattern_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\?)=sdf");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("sdf", templatePart.Default);
+            Assert.False(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\?)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithQuestionMarkInPattern_Optional_WithDefaultValue_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(\?)=sdf?");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Equal("sdf", templatePart.Default);
+            Assert.True(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\?)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithQuestionMarkInName_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"par?am:test(\?)");
+
+            // Assert
+            Assert.Equal("par?am", templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.False(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(\?)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithClosedParenAndColonInPattern_ParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(#):$)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.False(templatePart.IsOptional);
+
+            Assert.Collection(templatePart.Constraints,
+                constraint => Assert.Equal(@"test(#)", constraint.Content),
+                constraint => Assert.Equal(@"$)", constraint.Content));
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithColonAndClosedParenInPattern_PatternIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"param:test(#:)$)");
+
+            // Assert
+            Assert.Equal("param", templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.False(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"test(#:)$)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ContainingMultipleUnclosedParenthesisInConstraint()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"foo:regex(\\(\\(\\(\\()");
+
+            // Assert
+            Assert.Equal("foo", templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.False(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"regex(\\(\\(\\(\\()", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithBraces_PatternIsParsedCorrectly()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"p1:regex(^\d{{3}}-\d{{3}}-\d{{4}}$)"); // ssn
+
+            // Assert
+            Assert.Equal("p1", templatePart.Name);
+            Assert.Null(templatePart.Default);
+            Assert.False(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"regex(^\d{{3}}-\d{{3}}-\d{{4}}$)", constraint.Content);
+        }
+
+        [Fact]
+        public void ParseRouteParameter_ConstraintWithBraces_WithDefaultValue()
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(@"p1:regex(^\d{{3}}-\d{{3}}-\d{{4}}$)=123-456-7890"); // ssn
+
+            // Assert
+            Assert.Equal("p1", templatePart.Name);
+            Assert.Equal("123-456-7890", templatePart.Default);
+            Assert.False(templatePart.IsOptional);
+
+            var constraint = Assert.Single(templatePart.Constraints);
+            Assert.Equal(@"regex(^\d{{3}}-\d{{3}}-\d{{4}}$)", constraint.Content);
+        }
+
+        [Theory]
+        [InlineData("", "")]
+        [InlineData("?", "")]
+        [InlineData("*", "")]
+        [InlineData(" ", " ")]
+        [InlineData("\t", "\t")]
+        [InlineData("#!@#$%Q@#@%", "#!@#$%Q@#@%")]
+        [InlineData(",,,", ",,,")]
+        public void ParseRouteParameter_ParameterWithoutInlineConstraint_ReturnsTemplatePartWithEmptyInlineValues(
+                                                                                        string parameter,
+                                                                                        string expectedParameterName)
+        {
+            // Arrange & Act
+            var templatePart = ParseParameter(parameter);
+
+            // Assert
+            Assert.Equal(expectedParameterName, templatePart.Name);
+            Assert.Empty(templatePart.Constraints);
+            Assert.Null(templatePart.Default);
+        }
+
+        private RoutePatternParameterPart ParseParameter(string routeParameter)
+        {
+            // See: #475 - these tests don't pass the 'whole' text.
+            var templatePart = RouteParameterParser.ParseRouteParameter(routeParameter);
+            return templatePart;
+        }
+    }
+}

test/Microsoft.AspNetCore.Routing.Tests/Patterns/RoutePatternFactoryTest.cs

@@ -0,0 +1,247 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq;
+using Microsoft.AspNetCore.Routing.Constraints;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    public class RoutePatternFactoryTest
+    {
+        [Fact]
+        public void Pattern_MergesDefaultValues()
+        {
+            // Arrange
+            var template = "{a}/{b}/{c=19}";
+            var defaults = new { a = "15", b = 17 };
+            var constraints = new { };
+
+            var original = RoutePatternFactory.Parse(template);
+
+            // Act
+            var actual = RoutePatternFactory.Pattern(
+                original.RawText,
+                defaults,
+                constraints,
+                original.PathSegments);
+
+            // Assert
+            Assert.Equal("15", actual.GetParameter("a").Default);
+            Assert.Equal(17, actual.GetParameter("b").Default);
+            Assert.Equal("19", actual.GetParameter("c").Default);
+
+            Assert.Collection(
+                actual.Defaults.OrderBy(kvp => kvp.Key),
+                kvp => { Assert.Equal("a", kvp.Key); Assert.Equal("15", kvp.Value); },
+                kvp => { Assert.Equal("b", kvp.Key); Assert.Equal(17, kvp.Value); },
+                kvp => { Assert.Equal("c", kvp.Key); Assert.Equal("19", kvp.Value); });
+        }
+
+        [Fact]
+        public void Pattern_ExtraDefaultValues()
+        {
+            // Arrange
+            var template = "{a}/{b}/{c}";
+            var defaults = new { d = "15", e = 17 };
+            var constraints = new { };
+
+            var original = RoutePatternFactory.Parse(template);
+
+            // Act
+            var actual = RoutePatternFactory.Pattern(
+                original.RawText,
+                defaults,
+                constraints,
+                original.PathSegments);
+
+            // Assert
+            Assert.Collection(
+                actual.Defaults.OrderBy(kvp => kvp.Key),
+                kvp => { Assert.Equal("d", kvp.Key); Assert.Equal("15", kvp.Value); },
+                kvp => { Assert.Equal("e", kvp.Key); Assert.Equal(17, kvp.Value); });
+        }
+
+        [Fact]
+        public void Pattern_DuplicateDefaultValue_Throws()
+        {
+            // Arrange
+            var template = "{a=13}/{b}/{c}";
+            var defaults = new { a = "15", };
+            var constraints = new { };
+
+            var original = RoutePatternFactory.Parse(template);
+
+            // Act
+            var ex = Assert.Throws<InvalidOperationException>(() => RoutePatternFactory.Pattern(
+                original.RawText,
+                defaults,
+                constraints,
+                original.PathSegments));
+
+            // Assert
+            Assert.Equal(
+                "The route parameter 'a' has both an inline default value and an explicit default " +
+                "value specified. A route parameter cannot contain an inline default value when a " +
+                "default value is specified explicitly. Consider removing one of them.",
+                ex.Message);
+        }
+
+        [Fact]
+        public void Pattern_OptionalParameterDefaultValue_Throws()
+        {
+            // Arrange
+            var template = "{a}/{b}/{c?}";
+            var defaults = new { c = "15", };
+            var constraints = new { };
+
+            var original = RoutePatternFactory.Parse(template);
+
+            // Act
+            var ex = Assert.Throws<InvalidOperationException>(() => RoutePatternFactory.Pattern(
+                original.RawText,
+                defaults,
+                constraints,
+                original.PathSegments));
+
+            // Assert
+            Assert.Equal(
+                "An optional parameter cannot have default value.",
+                ex.Message);
+        }
+
+        [Fact]
+        public void Pattern_MergesConstraints()
+        {
+            // Arrange
+            var template = "{a:int}/{b}/{c}";
+            var defaults = new { };
+            var constraints = new { a = new RegexRouteConstraint("foo"), b = new RegexRouteConstraint("bar") };
+
+            var original = RoutePatternFactory.Parse(template);
+
+            // Act
+            var actual = RoutePatternFactory.Pattern(
+                original.RawText,
+                defaults,
+                constraints,
+                original.PathSegments);
+
+            // Assert
+            Assert.Collection(
+                actual.GetParameter("a").Constraints,
+                c => Assert.IsType<RegexRouteConstraint>(c.Constraint),
+                c => Assert.Equal("int", c.Content));
+            Assert.Collection(
+                actual.GetParameter("b").Constraints,
+                c => Assert.IsType<RegexRouteConstraint>(c.Constraint));
+
+            Assert.Collection(
+                actual.Constraints.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Equal("a", kvp.Key);
+                    Assert.Collection(
+                        kvp.Value,
+                        c => Assert.IsType<RegexRouteConstraint>(c.Constraint),
+                        c => Assert.Equal("int", c.Content));
+                },
+                kvp =>
+                {
+                    Assert.Equal("b", kvp.Key);
+                    Assert.Collection(
+                        kvp.Value,
+                        c => Assert.IsType<RegexRouteConstraint>(c.Constraint));
+                });
+        }
+
+        [Fact]
+        public void Pattern_ExtraConstraints()
+        {
+            // Arrange
+            var template = "{a}/{b}/{c}";
+            var defaults = new { };
+            var constraints = new { d = new RegexRouteConstraint("foo"), e = new RegexRouteConstraint("bar") };
+
+            var original = RoutePatternFactory.Parse(template);
+
+            // Act
+            var actual = RoutePatternFactory.Pattern(
+                original.RawText,
+                defaults,
+                constraints,
+                original.PathSegments);
+
+            // Assert
+            Assert.Collection(
+                actual.Constraints.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Equal("d", kvp.Key);
+                    Assert.Collection(
+                        kvp.Value,
+                        c => Assert.IsType<RegexRouteConstraint>(c.Constraint));
+                },
+                kvp =>
+                {
+                    Assert.Equal("e", kvp.Key);
+                    Assert.Collection(
+                        kvp.Value,
+                        c => Assert.IsType<RegexRouteConstraint>(c.Constraint));
+                });
+        }
+
+        [Fact]
+        public void Pattern_CreatesConstraintFromString()
+        {
+            // Arrange
+            var template = "{a}/{b}/{c}";
+            var defaults = new { };
+            var constraints = new { d = "foo", };
+
+            var original = RoutePatternFactory.Parse(template);
+
+            // Act
+            var actual = RoutePatternFactory.Pattern(
+                original.RawText,
+                defaults,
+                constraints,
+                original.PathSegments);
+
+            // Assert
+            Assert.Collection(
+                actual.Constraints.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Equal("d", kvp.Key);
+                    var regex = Assert.IsType<RegexRouteConstraint>(Assert.Single(kvp.Value).Constraint);
+                    Assert.Equal("^(foo)$", regex.Constraint.ToString());
+                });
+        }
+
+        [Fact]
+        public void Pattern_InvalidConstraintTypeThrows()
+        {
+            // Arrange
+            var template = "{a}/{b}/{c}";
+            var defaults = new { };
+            var constraints = new { d = 17, };
+
+            var original = RoutePatternFactory.Parse(template);
+
+            // Act
+            var ex = Assert.Throws<InvalidOperationException>(() => RoutePatternFactory.Pattern(
+                original.RawText,
+                defaults,
+                constraints,
+                original.PathSegments));
+
+            // Assert
+            Assert.Equal(
+                "The constraint entry 'd' - '17' must have a string value or be of a type " +
+                "which implements 'Microsoft.AspNetCore.Routing.IRouteConstraint'.",
+                ex.Message);
+        }
+    }
+}

test/Microsoft.AspNetCore.Routing.Tests/Patterns/RoutePatternParserTest.cs

@@ -0,0 +1,765 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using Microsoft.AspNetCore.Testing;
+using Xunit;
+using static Microsoft.AspNetCore.Routing.Patterns.RoutePatternFactory;
+
+namespace Microsoft.AspNetCore.Routing.Patterns
+{
+    public class RoutePatternParameterParserTest
+    {
+        [Fact]
+        public void Parse_SingleLiteral()
+        {
+            // Arrange
+            var template = "cool";
+
+            var expected = Pattern(
+                template,
+                Segment(LiteralPart("cool")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_SingleParameter()
+        {
+            // Arrange
+            var template = "{p}";
+
+            var expected = Pattern(template, Segment(ParameterPart("p")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_OptionalParameter()
+        {
+            // Arrange
+            var template = "{p?}";
+
+            var expected = Pattern(template, Segment(ParameterPart("p", null, RoutePatternParameterKind.Optional)));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_MultipleLiterals()
+        {
+            // Arrange
+            var template = "cool/awesome/super";
+
+            var expected = Pattern(
+                template,
+                Segment(LiteralPart("cool")),
+                Segment(LiteralPart("awesome")),
+                Segment(LiteralPart("super")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_MultipleParameters()
+        {
+            // Arrange
+            var template = "{p1}/{p2}/{*p3}";
+
+            var expected = Pattern(
+                template,
+                Segment(ParameterPart("p1")),
+                Segment(ParameterPart("p2")),
+                Segment(ParameterPart("p3", null, RoutePatternParameterKind.CatchAll)));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_LP()
+        {
+            // Arrange
+            var template = "cool-{p1}";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    LiteralPart("cool-"),
+                    ParameterPart("p1")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_PL()
+        {
+            // Arrange
+            var template = "{p1}-cool";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart("p1"),
+                    LiteralPart("-cool")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_PLP()
+        {
+            // Arrange
+            var template = "{p1}-cool-{p2}";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart("p1"),
+                    LiteralPart("-cool-"),
+                    ParameterPart("p2")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_LPL()
+        {
+            // Arrange
+            var template = "cool-{p1}-awesome";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    LiteralPart("cool-"),
+                    ParameterPart("p1"),
+                    LiteralPart("-awesome")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_OptionalParameterFollowingPeriod()
+        {
+            // Arrange
+            var template = "{p1}.{p2?}";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart("p1"),
+                    SeparatorPart("."),
+                    ParameterPart("p2", null, RoutePatternParameterKind.Optional)));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_ParametersFollowingPeriod()
+        {
+            // Arrange
+            var template = "{p1}.{p2}";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart("p1"),
+                    LiteralPart("."),
+                    ParameterPart("p2")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_OptionalParameterFollowingPeriod_ThreeParameters()
+        {
+            // Arrange
+            var template = "{p1}.{p2}.{p3?}";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart("p1"),
+                    LiteralPart("."),
+                    ParameterPart("p2"),
+                    SeparatorPart("."),
+                    ParameterPart("p3", null, RoutePatternParameterKind.Optional)));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_ThreeParametersSeperatedByPeriod()
+        {
+            // Arrange
+            var template = "{p1}.{p2}.{p3}";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart("p1"),
+                    LiteralPart("."),
+                    ParameterPart("p2"),
+                    LiteralPart("."),
+                    ParameterPart("p3")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_OptionalParameterFollowingPeriod_MiddleSegment()
+        {
+            // Arrange
+            var template = "{p1}.{p2?}/{p3}";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart("p1"),
+                    SeparatorPart("."),
+                    ParameterPart("p2", null, RoutePatternParameterKind.Optional)),
+                Segment(
+                    ParameterPart("p3")));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_OptionalParameterFollowingPeriod_LastSegment()
+        {
+            // Arrange
+            var template = "{p1}/{p2}.{p3?}";
+
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart("p1")),
+                Segment(
+                    ParameterPart("p2"),
+                    SeparatorPart("."),
+                    ParameterPart("p3", null, RoutePatternParameterKind.Optional)));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Fact]
+        public void Parse_ComplexSegment_OptionalParameterFollowingPeriod_PeriodAfterSlash()
+        {
+            // Arrange
+            var template = "{p2}/.{p3?}";
+
+            var expected = Pattern(
+                template,
+                Segment(ParameterPart("p2")),
+                Segment(
+                    SeparatorPart("."),
+                    ParameterPart("p3", null, RoutePatternParameterKind.Optional)));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Theory]
+        [InlineData(@"{p1:regex(^\d{{3}}-\d{{3}}-\d{{4}}$)}", @"regex(^\d{3}-\d{3}-\d{4}$)")] // ssn
+        [InlineData(@"{p1:regex(^\d{{1,2}}\/\d{{1,2}}\/\d{{4}}$)}", @"regex(^\d{1,2}\/\d{1,2}\/\d{4}$)")] // date
+        [InlineData(@"{p1:regex(^\w+\@\w+\.\w+)}", @"regex(^\w+\@\w+\.\w+)")] // email
+        [InlineData(@"{p1:regex(([}}])\w+)}", @"regex(([}])\w+)")] // Not balanced }
+        [InlineData(@"{p1:regex(([{{(])\w+)}", @"regex(([{(])\w+)")] // Not balanced {
+        public void Parse_RegularExpressions(string template, string constraint)
+        {
+            // Arrange
+            var expected = Pattern(
+                template,
+                Segment(
+                    ParameterPart(
+                        "p1",
+                        null,
+                        RoutePatternParameterKind.Standard,
+                        Constraint("p1", constraint))));
+
+            // Act
+            var actual = RoutePatternParser.Parse(template);
+
+            // Assert
+            Assert.Equal<RoutePattern>(expected, actual, new RoutePatternEqualityComparer());
+        }
+
+        [Theory]
+        [InlineData(@"{p1:regex(^\d{{3}}-\d{{3}}-\d{{4}}}$)}")] // extra }
+        [InlineData(@"{p1:regex(^\d{{3}}-\d{{3}}-\d{{4}}$)}}")] // extra } at the end
+        [InlineData(@"{{p1:regex(^\d{{3}}-\d{{3}}-\d{{4}}$)}")] // extra { at the begining
+        [InlineData(@"{p1:regex(([}])\w+}")] // Not escaped }
+        [InlineData(@"{p1:regex(^\d{{3}}-\d{{3}}-\d{{4}$)}")] // Not escaped }
+        [InlineData(@"{p1:regex(abc)")]
+        public void Parse_RegularExpressions_Invalid(string template)
+        {
+            // Act and Assert
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse(template),
+                "There is an incomplete parameter in the route template. Check that each '{' character has a matching " +
+                "'}' character.");
+        }
+
+        [Theory]
+        [InlineData(@"{p1:regex(^\d{{3}}-\d{{3}}-\d{{{4}}$)}")] // extra {
+        [InlineData(@"{p1:regex(^\d{{3}}-\d{{3}}-\d{4}}$)}")] // Not escaped {
+        public void Parse_RegularExpressions_Unescaped(string template)
+        {
+            // Act and Assert
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse(template),
+                "In a route parameter, '{' and '}' must be escaped with '{{' and '}}'.");
+        }
+
+        [Theory]
+        [InlineData("{p1}.{p2?}.{p3}", "p2", ".")]
+        [InlineData("{p1?}{p2}", "p1", "{p2}")]
+        [InlineData("{p1?}{p2?}", "p1", "{p2?}")]
+        [InlineData("{p1}.{p2?})", "p2", ")")]
+        [InlineData("{foorb?}-bar-{z}", "foorb", "-bar-")]
+        public void Parse_ComplexSegment_OptionalParameter_NotTheLastPart(
+            string template,
+            string parameter,
+            string invalid)
+        {
+            // Act and Assert
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse(template),
+                "An optional parameter must be at the end of the segment. In the segment '" + template +
+                "', optional parameter '" + parameter + "' is followed by '" + invalid + "'.");
+        }
+
+        [Theory]
+        [InlineData("{p1}-{p2?}", "-")]
+        [InlineData("{p1}..{p2?}", "..")]
+        [InlineData("..{p2?}", "..")]
+        [InlineData("{p1}.abc.{p2?}", ".abc.")]
+        [InlineData("{p1}{p2?}", "{p1}")]
+        public void Parse_ComplexSegment_OptionalParametersSeperatedByPeriod_Invalid(string template, string parameter)
+        {
+            // Act and Assert
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse(template),
+                "In the segment '" + template + "', the optional parameter 'p2' is preceded by an invalid " +
+                "segment '" + parameter + "'. Only a period (.) can precede an optional parameter.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_WithRepeatedParameter()
+        {
+            var ex = ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{Controller}.mvc/{id}/{controller}"),
+                "The route parameter name 'controller' appears more than one time in the route template.");
+        }
+
+        [Theory]
+        [InlineData("123{a}abc{")]
+        [InlineData("123{a}abc}")]
+        [InlineData("xyz}123{a}abc}")]
+        [InlineData("{{p1}")]
+        [InlineData("{p1}}")]
+        [InlineData("p1}}p2{")]
+        public void InvalidTemplate_WithMismatchedBraces(string template)
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse(template),
+                @"There is an incomplete parameter in the route template. Check that each '{' character has a " +
+                "matching '}' character.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_CannotHaveCatchAllInMultiSegment()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("123{a}abc{*moo}"),
+                "A path segment that contains more than one section, such as a literal section or a parameter, " +
+                "cannot contain a catch-all parameter.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_CannotHaveMoreThanOneCatchAll()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{*p1}/{*p2}"),
+                "A catch-all parameter can only appear as the last segment of the route template.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_CannotHaveMoreThanOneCatchAllInMultiSegment()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{*p1}abc{*p2}"),
+                "A path segment that contains more than one section, such as a literal section or a parameter, " +
+                "cannot contain a catch-all parameter.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_CannotHaveCatchAllWithNoName()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("foo/{*}"),
+                "The route parameter name '' is invalid. Route parameter names must be non-empty and cannot" +
+                " contain these characters: '{', '}', '/'. The '?' character marks a parameter as optional," +
+                " and can occur only at the end of the parameter. The '*' character marks a parameter as catch-all," +
+                " and can occur only at the start of the parameter.");
+        }
+
+        [Theory]
+        [InlineData("{**}", "*")]
+        [InlineData("{a*}", "a*")]
+        [InlineData("{*a*}", "a*")]
+        [InlineData("{*a*:int}", "a*")]
+        [InlineData("{*a*=5}", "a*")]
+        [InlineData("{*a*b=5}", "a*b")]
+        [InlineData("{p1?}.{p2/}/{p3}", "p2/")]
+        [InlineData("{p{{}", "p{")]
+        [InlineData("{p}}}", "p}")]
+        [InlineData("{p/}", "p/")]
+        public void ParseRouteParameter_ThrowsIf_ParameterContainsSpecialCharacters(
+            string template,
+            string parameterName)
+        {
+            // Arrange
+            var expectedMessage = "The route parameter name '" + parameterName + "' is invalid. Route parameter " +
+                "names must be non-empty and cannot contain these characters: '{', '}', '/'. The '?' character " +
+                "marks a parameter as optional, and can occur only at the end of the parameter. The '*' character " +
+                "marks a parameter as catch-all, and can occur only at the start of the parameter.";
+
+            // Act & Assert
+            ExceptionAssert.Throws<RoutePatternException>(() => RoutePatternParser.Parse(template), expectedMessage);
+        }
+
+        [Fact]
+        public void InvalidTemplate_CannotHaveConsecutiveOpenBrace()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("foo/{{p1}"),
+                "There is an incomplete parameter in the route template. Check that each '{' character has a " +
+                "matching '}' character.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_CannotHaveConsecutiveCloseBrace()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("foo/{p1}}"),
+                "There is an incomplete parameter in the route template. Check that each '{' character has a " +
+                "matching '}' character.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_SameParameterTwiceThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{aaa}/{AAA}"),
+                "The route parameter name 'AAA' appears more than one time in the route template.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_SameParameterTwiceAndOneCatchAllThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{aaa}/{*AAA}"),
+                "The route parameter name 'AAA' appears more than one time in the route template.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_InvalidParameterNameWithCloseBracketThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{a}/{aa}a}/{z}"),
+                "There is an incomplete parameter in the route template. Check that each '{' character has a " +
+                "matching '}' character.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_InvalidParameterNameWithOpenBracketThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{a}/{a{aa}/{z}"),
+                "In a route parameter, '{' and '}' must be escaped with '{{' and '}}'.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_InvalidParameterNameWithEmptyNameThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{a}/{}/{z}"),
+                "The route parameter name '' is invalid. Route parameter names must be non-empty and cannot" +
+                " contain these characters: '{', '}', '/'. The '?' character marks a parameter as optional, and" +
+                " can occur only at the end of the parameter. The '*' character marks a parameter as catch-all," +
+                " and can occur only at the start of the parameter.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_InvalidParameterNameWithQuestionThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{Controller}.mvc/{?}"),
+                "The route parameter name '' is invalid. Route parameter names must be non-empty and cannot" +
+                " contain these characters: '{', '}', '/'. The '?' character marks a parameter as optional, and" +
+                " can occur only at the end of the parameter. The '*' character marks a parameter as catch-all," +
+                " and can occur only at the start of the parameter.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_ConsecutiveSeparatorsSlashSlashThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{a}//{z}"),
+                "The route template separator character '/' cannot appear consecutively. It must be separated by " +
+                "either a parameter or a literal value.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_WithCatchAllNotAtTheEndThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("foo/{p1}/{*p2}/{p3}"),
+                "A catch-all parameter can only appear as the last segment of the route template.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_RepeatedParametersThrows()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("foo/aa{p1}{p2}"),
+                "A path segment cannot contain two consecutive parameters. They must be separated by a '/' or by " +
+                "a literal string.");
+        }
+
+        [Theory]
+        [InlineData("/foo")]
+        [InlineData("~/foo")]
+        public void ValidTemplate_CanStartWithSlashOrTildeSlash(string routePattern)
+        {
+            // Arrange & Act
+            var pattern = RoutePatternParser.Parse(routePattern);
+
+            // Assert
+            Assert.Equal(routePattern, pattern.RawText);
+        }
+
+        [Fact]
+        public void InvalidTemplate_CannotStartWithTilde()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("~foo"),
+                "The route template cannot start with a '~' character unless followed by a '/'.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_CannotContainQuestionMark()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("foor?bar"),
+                "The literal section 'foor?bar' is invalid. Literal sections cannot contain the '?' character.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_ParameterCannotContainQuestionMark_UnlessAtEnd()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{foor?b}"),
+                "The route parameter name 'foor?b' is invalid. Route parameter names must be non-empty and cannot" +
+                " contain these characters: '{', '}', '/'. The '?' character marks a parameter as optional, and" +
+                " can occur only at the end of the parameter. The '*' character marks a parameter as catch-all," +
+                " and can occur only at the start of the parameter.");
+        }
+
+        [Fact]
+        public void InvalidTemplate_CatchAllMarkedOptional()
+        {
+            ExceptionAssert.Throws<RoutePatternException>(
+                () => RoutePatternParser.Parse("{a}/{*b?}"),
+                "A catch-all parameter cannot be marked optional.");
+        }
+
+        private class RoutePatternEqualityComparer :
+            IEqualityComparer<RoutePattern>,
+            IEqualityComparer<RoutePatternConstraintReference>
+        {
+            public bool Equals(RoutePattern x, RoutePattern y)
+            {
+                if (x == null && y == null)
+                {
+                    return true;
+                }
+                else if (x == null || y == null)
+                {
+                    return false;
+                }
+                else
+                {
+                    if (!string.Equals(x.RawText, y.RawText, StringComparison.Ordinal))
+                    {
+                        return false;
+                    }
+
+                    if (x.PathSegments.Count != y.PathSegments.Count)
+                    {
+                        return false;
+                    }
+
+                    for (int i = 0; i < x.PathSegments.Count; i++)
+                    {
+                        if (x.PathSegments[i].Parts.Count != y.PathSegments[i].Parts.Count)
+                        {
+                            return false;
+                        }
+
+                        for (int j = 0; j < x.PathSegments[i].Parts.Count; j++)
+                        {
+                            if (!Equals(x.PathSegments[i].Parts[j], y.PathSegments[i].Parts[j]))
+                            {
+                                return false;
+                            }
+                        }
+                    }
+
+                    if (x.Parameters.Count != y.Parameters.Count)
+                    {
+                        return false;
+                    }
+
+                    for (int i = 0; i < x.Parameters.Count; i++)
+                    {
+                        if (!Equals(x.Parameters[i], y.Parameters[i]))
+                        {
+                            return false;
+                        }
+                    }
+
+                    return true;
+                }
+            }
+
+            private bool Equals(RoutePatternPart x, RoutePatternPart y)
+            {
+                if (x.GetType() != y.GetType())
+                {
+                    return false;
+                }
+
+                if (x.IsLiteral && y.IsLiteral)
+                {
+                    return Equals((RoutePatternLiteralPart)x, (RoutePatternLiteralPart)y);
+                }
+                else if (x.IsParameter && y.IsParameter)
+                {
+                    return Equals((RoutePatternParameterPart)x, (RoutePatternParameterPart)y);
+                }
+                else if (x.IsSeparator && y.IsSeparator)
+                {
+                    return Equals((RoutePatternSeparatorPart)x, (RoutePatternSeparatorPart)y);
+                }
+
+                Debug.Fail("This should not be reachable. Do you need to update the comparison logic?");
+                return false;
+            }
+
+            private bool Equals(RoutePatternLiteralPart x, RoutePatternLiteralPart y)
+            {
+                return x.Content == y.Content;
+            }
+
+            private bool Equals(RoutePatternParameterPart x, RoutePatternParameterPart y)
+            {
+                return
+                    x.Name == y.Name &&
+                    x.Default == y.Default &&
+                    x.ParameterKind == y.ParameterKind &&
+                    Enumerable.SequenceEqual(x.Constraints, y.Constraints, this);
+
+            }
+
+            public bool Equals(RoutePatternConstraintReference x, RoutePatternConstraintReference y)
+            {
+                return
+                    x.ParameterName == y.ParameterName &&
+                    x.Content == y.Content &&
+                    x.Constraint == y.Constraint;
+            }
+
+            private bool Equals(RoutePatternSeparatorPart x, RoutePatternSeparatorPart y)
+            {
+                return x.Content == y.Content;
+            }
+
+            public int GetHashCode(RoutePattern obj)
+            {
+                throw new NotImplementedException();
+            }
+
+            public int GetHashCode(RoutePatternConstraintReference obj)
+            {
+                throw new NotImplementedException();
+            }
+        }
+    }
+}

test/Microsoft.AspNetCore.Routing.Tests/Template/TemplateParserTests.cs

@@ -5,9 +5,6 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Testing;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Options;
-using Moq;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Routing.Template.Tests
@@ -528,8 +525,8 @@ namespace Microsoft.AspNetCore.Routing.Template.Tests
 
         [Theory]
         [InlineData("{p1}.{p2?}.{p3}", "p2", ".")]
-        [InlineData("{p1?}{p2}", "p1", "p2")]
-        [InlineData("{p1?}{p2?}", "p1", "p2")]
+        [InlineData("{p1?}{p2}", "p1", "{p2}")]
+        [InlineData("{p1?}{p2?}", "p1", "{p2?}")]
         [InlineData("{p1}.{p2?})", "p2", ")")]
         [InlineData("{foorb?}-bar-{z}", "foorb", "-bar-")]
         public void Parse_ComplexSegment_OptionalParameter_NotTheLastPart(
@@ -655,18 +652,6 @@ namespace Microsoft.AspNetCore.Routing.Template.Tests
                 "Parameter name: routeTemplate");
         }
 
-        [Theory]
-        [InlineData("/foo")]
-        [InlineData("~/foo")]
-        public void ValidTemplate_CanStartWithSlashOrTildeSlash(string routeTemplate)
-        {
-            // Arrange & Act
-            var template = TemplateParser.Parse(routeTemplate);
-
-            // Assert
-            Assert.Equal(routeTemplate, template.TemplateText);
-        }
-
         [Fact]
         public void InvalidTemplate_CannotHaveConsecutiveOpenBrace()
         {
@@ -780,6 +765,18 @@ namespace Microsoft.AspNetCore.Routing.Template.Tests
                 "Parameter name: routeTemplate");
         }
 
+        [Theory]
+        [InlineData("/foo")]
+        [InlineData("~/foo")]
+        public void ValidTemplate_CanStartWithSlashOrTildeSlash(string routeTemplate)
+        {
+            // Arrange & Act
+            var pattern = TemplateParser.Parse(routeTemplate);
+
+            // Assert
+            Assert.Equal(routeTemplate, pattern.TemplateText);
+        }
+
         [Fact]
         public void InvalidTemplate_CannotStartWithTilde()
         {