Add extract method support for ref struct interfaces (#73619)

* Add extract method support for ref struct interfaces

The method extraction code uses ITypeParameterSymbol's constraints to generate the new method's text. This codepath had not yet been modified to support ITypeParameterSymbol.AllowsRefLikeType

This is in support of the "allows ref struct" on interfaces feature outlined here: #72124

This ref structs for interfaces feature was merged via this PR: #73567

src/EditorFeatures/CSharpTest/ExtractMethod/ExtractMethodTests.LanguageInteraction.cs

@@ -58,6 +58,39 @@ class Program
                 await TestExtractMethodAsync(code, expected);
             }
 
+            [Fact]
+            public async Task SelectTypeParameterWithAllowsRefStructAntiConstraint()
+            {
+                var code = """
+                    using System;
+
+                    class Program
+                    {
+                        void MyMethod1<TT>(TT tt) where TT : IDisposable, allows ref struct
+                        {
+                            [|tt.Dispose();|]
+                        }
+                    }
+                    """;
+                var expected = """
+                    using System;
+
+                    class Program
+                    {
+                        void MyMethod1<TT>(TT tt) where TT : IDisposable, allows ref struct
+                        {
+                            NewMethod(tt);
+                        }
+                    
+                        private static void NewMethod<TT>(TT tt) where TT : IDisposable, allows ref struct
+                        {
+                            tt.Dispose();
+                        }
+                    }
+                    """;
+
+                await TestExtractMethodAsync(code, expected);
+            }
             [Fact]
             public async Task SelectTypeParameter()
             {

src/Features/Core/Portable/ExtractMethod/MethodExtractor.CodeGenerator.cs

@@ -344,7 +344,7 @@ protected ImmutableArray<ITypeParameterSymbol> CreateMethodTypeParameters()
                 typeParameters.Add(CodeGenerationSymbolFactory.CreateTypeParameter(
                     parameter.GetAttributes(), parameter.Variance, parameter.Name, [], parameter.NullableAnnotation,
                     parameter.HasConstructorConstraint, parameter.HasReferenceTypeConstraint, parameter.HasUnmanagedTypeConstraint,
-                    parameter.HasValueTypeConstraint, parameter.HasNotNullConstraint, parameter.Ordinal));
+                    parameter.HasValueTypeConstraint, parameter.HasNotNullConstraint, parameter.AllowsRefLikeType, parameter.Ordinal));
             }
 
             return typeParameters.ToImmutableAndFree();

src/Workspaces/Core/Portable/Shared/Extensions/IMethodSymbolExtensions.cs

@@ -137,6 +137,7 @@ private static ImmutableArray<ITypeParameterSymbol> RenameTypeParameters(
                 typeParameter.HasValueTypeConstraint,
                 typeParameter.HasUnmanagedTypeConstraint,
                 typeParameter.HasNotNullConstraint,
+                typeParameter.AllowsRefLikeType,
                 typeParameter.Ordinal);
 
             newTypeParameters.Add(newTypeParameter);

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/Extensions/ITypeParameterSymbolExtensions.cs

@@ -74,6 +74,12 @@ private static void AddConstraintClauses(
             constraints.Add(ConstructorConstraint());
         }
 
+        if (typeParameter.AllowsRefLikeType)
+        {
+            // "allows ref struct" anti-constraint must be last
+            constraints.Add(AllowsConstraintClause([RefStructConstraint()]));
+        }
+
         if (constraints.Count == 0)
         {
             return;

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/CodeGenerationSymbolFactory.cs

@@ -322,7 +322,8 @@ public static ITypeParameterSymbol CreateTypeParameterSymbol(string name, int or
             attributes: default, varianceKind: VarianceKind.None,
             name: name, constraintTypes: [],
             hasConstructorConstraint: false, hasReferenceConstraint: false, hasValueConstraint: false,
-            hasUnmanagedConstraint: false, hasNotNullConstraint: false, ordinal: ordinal);
+            hasUnmanagedConstraint: false, hasNotNullConstraint: false, allowsRefLikeType: false,
+            ordinal: ordinal);
     }
 
     /// <summary>
@@ -338,9 +339,10 @@ public static ITypeParameterSymbol CreateTypeParameter(
         bool hasUnmanagedConstraint = false,
         bool hasValueConstraint = false,
         bool hasNotNullConstraint = false,
+        bool allowsRefLikeType = false,
         int ordinal = 0)
     {
-        return new CodeGenerationTypeParameterSymbol(null, attributes, varianceKind, name, nullableAnnotation, constraintTypes, hasConstructorConstraint, hasReferenceConstraint, hasValueConstraint, hasUnmanagedConstraint, hasNotNullConstraint, ordinal);
+        return new CodeGenerationTypeParameterSymbol(null, attributes, varianceKind, name, nullableAnnotation, constraintTypes, hasConstructorConstraint, hasReferenceConstraint, hasValueConstraint, hasUnmanagedConstraint, hasNotNullConstraint, allowsRefLikeType, ordinal);
     }
 
     /// <summary>

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationTypeParameterSymbol.cs

@@ -20,14 +20,15 @@ internal class CodeGenerationTypeParameterSymbol(
     bool hasValueConstraint,
     bool hasUnmanagedConstraint,
     bool hasNotNullConstraint,
+    bool allowsRefLikeType,
     int ordinal) : CodeGenerationTypeSymbol(containingType?.ContainingAssembly, containingType, attributes, Accessibility.NotApplicable, default, name, SpecialType.None, nullableAnnotation), ITypeParameterSymbol
 {
     public VarianceKind Variance { get; } = varianceKind;
     public ImmutableArray<ITypeSymbol> ConstraintTypes { get; internal set; } = constraintTypes;
     public bool HasConstructorConstraint { get; } = hasConstructorConstraint;
     public bool HasReferenceTypeConstraint { get; } = hasReferenceConstraint;
     public bool HasValueTypeConstraint { get; } = hasValueConstraint;
-    public bool AllowsRefLikeType => false;
+    public bool AllowsRefLikeType { get; } = allowsRefLikeType;
     public bool HasUnmanagedTypeConstraint { get; } = hasUnmanagedConstraint;
     public bool HasNotNullConstraint { get; } = hasNotNullConstraint;
     public int Ordinal { get; } = ordinal;
@@ -37,7 +38,8 @@ protected override CodeGenerationTypeSymbol CloneWithNullableAnnotation(Nullable
         return new CodeGenerationTypeParameterSymbol(
             this.ContainingType, this.GetAttributes(), this.Variance, this.Name, nullableAnnotation,
             this.ConstraintTypes, this.HasConstructorConstraint, this.HasReferenceTypeConstraint,
-            this.HasValueTypeConstraint, this.HasUnmanagedTypeConstraint, this.HasNotNullConstraint, this.Ordinal);
+            this.HasValueTypeConstraint, this.HasUnmanagedTypeConstraint, this.HasNotNullConstraint,
+            this.AllowsRefLikeType, this.Ordinal);
     }
 
     public new ITypeParameterSymbol OriginalDefinition => this;