Remove constraints from Regex source generator partial class declaration (#63637)

Author: stephentoub

src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.Emitter.cs

@@ -1,7 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System;
 using System.Buffers.Binary;
 using System.CodeDom.Compiler;
 using System.Collections;
@@ -11,10 +10,7 @@
 using System.Globalization;
 using System.IO;
 using System.Linq;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using System.Security.Cryptography;
-using System.Text;
 using System.Threading;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
@@ -59,7 +55,7 @@ private static (string, ImmutableArray<Diagnostic>) EmitRegexType(RegexType rege
             var parentClasses = new Stack<string>();
             while (parent is not null)
             {
-                parentClasses.Push($"partial {parent.Keyword} {parent.Name} {parent.Constraints}");
+                parentClasses.Push($"partial {parent.Keyword} {parent.Name}");
                 parent = parent.ParentClass;
             }
             while (parentClasses.Count != 0)
@@ -70,7 +66,7 @@ private static (string, ImmutableArray<Diagnostic>) EmitRegexType(RegexType rege
             }
 
             // Emit the direct parent type
-            writer.WriteLine($"partial {regexClass.Keyword} {regexClass.Name} {regexClass.Constraints}");
+            writer.WriteLine($"partial {regexClass.Keyword} {regexClass.Name}");
             writer.WriteLine("{");
             writer.Indent++;
 

src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.Parser.cs

@@ -202,8 +202,7 @@ private static bool IsSyntaxTargetForGeneration(SyntaxNode node) =>
                 regexMethod,
                 typeDec is RecordDeclarationSyntax rds ? $"{typeDec.Keyword.ValueText} {rds.ClassOrStructKeyword}" : typeDec.Keyword.ValueText,
                 ns ?? string.Empty,
-                $"{typeDec.Identifier}{typeDec.TypeParameterList}",
-                typeDec.ConstraintClauses.ToString());
+                $"{typeDec.Identifier}{typeDec.TypeParameterList}");
 
             RegexType current = regexType;
             var parent = typeDec.Parent as TypeDeclarationSyntax;
@@ -214,8 +213,7 @@ private static bool IsSyntaxTargetForGeneration(SyntaxNode node) =>
                     null,
                     parent is RecordDeclarationSyntax rds2 ? $"{parent.Keyword.ValueText} {rds2.ClassOrStructKeyword}" : parent.Keyword.ValueText,
                     ns ?? string.Empty,
-                    $"{parent.Identifier}{parent.TypeParameterList}",
-                    parent.ConstraintClauses.ToString());
+                    $"{parent.Identifier}{parent.TypeParameterList}");
 
                 current = current.ParentClass;
                 parent = parent.Parent as TypeDeclarationSyntax;
@@ -235,7 +233,7 @@ static bool IsAllowedKind(SyntaxKind kind) =>
         internal sealed record RegexMethod(MethodDeclarationSyntax MethodSyntax, string MethodName, string Modifiers, string Pattern, RegexOptions Options, int MatchTimeout, RegexCode Code);
 
         /// <summary>A type holding a regex method.</summary>
-        internal sealed record RegexType(RegexMethod? Method, string Keyword, string Namespace, string Name, string Constraints)
+        internal sealed record RegexType(RegexMethod? Method, string Keyword, string Namespace, string Name)
         {
             public RegexType? ParentClass { get; set; }
         }

src/libraries/System.Text.RegularExpressions/tests/System.Text.RegularExpressions.Generators.Tests/RegexGeneratorParserTests.cs

@@ -442,6 +442,30 @@ partial class C
             ", compile: true));
         }
 
+        [Fact]
+        public async Task Valid_ClassWithGenericConstraints()
+        {
+            Assert.Empty(await RunGenerator(@"
+                using D;
+                using System.Text.RegularExpressions;
+                namespace A
+                {
+                    public partial class B<U>
+                    {
+                        private partial class C<T> where T : IBlah
+                        {
+                            [RegexGenerator(""ab"")]
+                            private static partial Regex Valid();
+                        }
+                    }
+                }
+                namespace D
+                {
+                    internal interface IBlah { }
+                }
+            ", compile: true));
+        }
+
         public static IEnumerable<object[]> Valid_Modifiers_MemberData()
         {
             foreach (string type in new[] { "class", "struct", "record", "record struct", "record class", "interface" })