Fix find refs

Author: CyrusNajmabadi

src/Compilers/CSharp/Portable/Symbols/PublicModel/TypeSymbol.cs

@@ -151,6 +151,8 @@ TypeKind ITypeSymbol.TypeKind
 
         bool ITypeSymbol.IsExtension => UnderlyingTypeSymbol.IsExtension;
 
+        IParameterSymbol ITypeSymbol.ExtensionParameter => UnderlyingTypeSymbol.ExtensionParameter?.GetPublicSymbol();
+
         string ITypeSymbol.ToDisplayString(CodeAnalysis.NullableFlowState topLevelNullability, SymbolDisplayFormat format)
         {
             return SymbolDisplay.ToDisplayString(this, topLevelNullability, format);

src/Compilers/Core/Portable/PublicAPI.Unshipped.txt

@@ -2,7 +2,7 @@ Microsoft.CodeAnalysis.IEventSymbol.IsPartialDefinition.get -> bool
 Microsoft.CodeAnalysis.IEventSymbol.PartialDefinitionPart.get -> Microsoft.CodeAnalysis.IEventSymbol?
 Microsoft.CodeAnalysis.IEventSymbol.PartialImplementationPart.get -> Microsoft.CodeAnalysis.IEventSymbol?
 Microsoft.CodeAnalysis.IncrementalGeneratorPostInitializationContext.AddEmbeddedAttributeDefinition() -> void
+Microsoft.CodeAnalysis.ITypeSymbol.ExtensionParameter.get -> Microsoft.CodeAnalysis.IParameterSymbol?
 override Microsoft.CodeAnalysis.Diagnostics.AnalyzerFileReference.ToString() -> string!
-
 Microsoft.CodeAnalysis.ITypeSymbol.IsExtension.get -> bool
 Microsoft.CodeAnalysis.TypeKind.Extension = 14 -> Microsoft.CodeAnalysis.TypeKind

src/Compilers/Core/Portable/Symbols/ITypeSymbol.cs

@@ -86,6 +86,11 @@ public interface ITypeSymbol : INamespaceOrTypeSymbol
         /// </summary>
         bool IsExtension { get; }
 
+        /// <summary>
+        /// The extension parameter if this is an extension declaration (<see cref="IsExtension"/> is true).
+        /// </summary>
+        IParameterSymbol? ExtensionParameter { get; }
+
         /// <summary>
         /// The original definition of this symbol. If this symbol is constructed from another
         /// symbol by type substitution then <see cref="OriginalDefinition"/> gets the original symbol as it was defined in

src/Compilers/VisualBasic/Portable/Symbols/TypeSymbol.vb

@@ -789,5 +789,10 @@ Done:
             End Get
         End Property
 
+        Public ReadOnly Property ExtensionParameter As IParameterSymbol Implements ITypeSymbol.ExtensionParameter
+            Get
+                Return Nothing
+            End Get
+        End Property
     End Class
 End Namespace

src/Features/Core/Portable/MetadataAsSource/AbstractMetadataAsSourceService.WrappedNamedTypeSymbol.cs

@@ -146,6 +146,8 @@ public ImmutableArray<SymbolDisplayPart> ToMinimalDisplayParts(SemanticModel sem
 
         public bool IsExtension => _symbol.IsExtension;
 
+        public IParameterSymbol ExtensionParameter => _symbol.ExtensionParameter;
+
         public bool IsFileLocal => _symbol.IsFileLocal;
 
         public INamedTypeSymbol NativeIntegerUnderlyingType => _symbol.NativeIntegerUnderlyingType;

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.NamedTypeSymbolKey.cs

@@ -2,9 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections.Immutable;
-using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis;
 
@@ -19,21 +17,16 @@ public sealed override void Create(INamedTypeSymbol symbol, SymbolKeyWriter visi
             visitor.WriteSymbolKey(symbol.ContainingSymbol);
             visitor.WriteString(symbol.Name);
             visitor.WriteInteger(symbol.Arity);
-            visitor.WriteString(symbol.IsFileLocal
-                ? symbol.DeclaringSyntaxReferences[0].SyntaxTree.FilePath
-                : null);
+            // Include the metadata name for extensions.  We need this to uniquely find it when resolving.
+            visitor.WriteString(symbol.IsExtension ? symbol.MetadataName : null);
+            // Include the file path for 'file-local' types.  We need this to uniquely find it when resolving.
+            visitor.WriteString(symbol.IsFileLocal ? symbol.DeclaringSyntaxReferences[0].SyntaxTree.FilePath : null);
             visitor.WriteBoolean(symbol.IsUnboundGenericType);
             visitor.WriteBoolean(symbol.IsNativeIntegerType);
             visitor.WriteBoolean(symbol.SpecialType == SpecialType.System_IntPtr);
 
-            if (!symbol.Equals(symbol.ConstructedFrom) && !symbol.IsUnboundGenericType)
-            {
-                visitor.WriteSymbolKeyArray(symbol.TypeArguments);
-            }
-            else
-            {
-                visitor.WriteSymbolKeyArray(ImmutableArray<ITypeSymbol>.Empty);
-            }
+            visitor.WriteSymbolKeyArray(
+                symbol.Equals(symbol.ConstructedFrom) || symbol.IsUnboundGenericType ? [] : symbol.TypeArguments);
         }
 
         protected sealed override SymbolKeyResolution Resolve(
@@ -42,6 +35,7 @@ protected sealed override SymbolKeyResolution Resolve(
             var containingSymbolResolution = reader.ReadSymbolKey(contextualSymbol?.ContainingSymbol, out var containingSymbolFailureReason);
             var name = reader.ReadRequiredString();
             var arity = reader.ReadInteger();
+            var extensionMetadataName = reader.ReadString();
             var filePath = reader.ReadString();
             var isUnboundGenericType = reader.ReadBoolean();
             var isNativeIntegerType = reader.ReadBoolean();
@@ -73,7 +67,8 @@ protected sealed override SymbolKeyResolution Resolve(
 
             var normalResolution = ResolveNormalNamedType(
                 containingSymbolResolution, containingSymbolFailureReason,
-                name, arity, filePath, isUnboundGenericType, typeArgumentsArray,
+                name, extensionMetadataName, arity, filePath,
+                isUnboundGenericType, typeArgumentsArray,
                 out failureReason);
 
             if (normalResolution.SymbolCount > 0)
@@ -140,10 +135,11 @@ private static SymbolKeyResolution ResolveNormalNamedType(
             SymbolKeyResolution containingSymbolResolution,
             string? containingSymbolFailureReason,
             string name,
+            string? extensionMetadataName,
             int arity,
             string? filePath,
             bool isUnboundGenericType,
-            ITypeSymbol[] typeArgumentsArray,
+            ITypeSymbol[] typeArguments,
             out string? failureReason)
         {
             if (containingSymbolFailureReason != null)
@@ -154,43 +150,46 @@ private static SymbolKeyResolution ResolveNormalNamedType(
 
             using var result = PooledArrayBuilder<INamedTypeSymbol>.GetInstance();
             foreach (var nsOrType in containingSymbolResolution.OfType<INamespaceOrTypeSymbol>())
-            {
-                Resolve(
-                    result, nsOrType, name, arity, filePath,
-                    isUnboundGenericType, typeArgumentsArray);
-            }
+                Resolve(nsOrType, result);
 
             return CreateResolution(result, $"({nameof(NamedTypeSymbolKey)} failed)", out failureReason);
-        }
 
-        private static void Resolve(
-            PooledArrayBuilder<INamedTypeSymbol> result,
-            INamespaceOrTypeSymbol container,
-            string name,
-            int arity,
-            string? filePath,
-            bool isUnboundGenericType,
-            ITypeSymbol[] typeArguments)
-        {
-            foreach (var type in container.GetTypeMembers(name, arity))
+            void Resolve(
+                INamespaceOrTypeSymbol container,
+                PooledArrayBuilder<INamedTypeSymbol> result)
             {
-                // if this is a file-local type, then only resolve to a file-local type from this same file
-                if (filePath != null)
+                if (extensionMetadataName != null)
                 {
-                    if (!type.IsFileLocal ||
-                        // note: if we found 'IsFile' returned true, we can assume DeclaringSyntaxReferences is non-empty.
-                        type.DeclaringSyntaxReferences[0].SyntaxTree.FilePath != filePath)
+                    // Unfortunately, no fast index from metadata name to type, so we have to iterate all nested types.
+                    foreach (var type in container.GetTypeMembers())
                     {
-                        continue;
+                        if (type.MetadataName == extensionMetadataName)
+                            result.AddIfNotNull(Construct(type, isUnboundGenericType, typeArguments));
                     }
                 }
-                else if (type.IsFileLocal)
+                else
                 {
-                    // since this key lacks a file path it can't match against a file-local type
-                    continue;
+                    foreach (var type in container.GetTypeMembers(name, arity))
+                    {
+                        // if this is a file-local type, then only resolve to a file-local type from this same file
+                        if (filePath != null)
+                        {
+                            if (!type.IsFileLocal ||
+                                // note: if we found 'IsFile' returned true, we can assume DeclaringSyntaxReferences is non-empty.
+                                type.DeclaringSyntaxReferences[0].SyntaxTree.FilePath != filePath)
+                            {
+                                continue;
+                            }
+                        }
+                        else if (type.IsFileLocal)
+                        {
+                            // since this key lacks a file path it can't match against a file-local type
+                            continue;
+                        }
+
+                        result.AddIfNotNull(Construct(type, isUnboundGenericType, typeArguments));
+                    }
                 }
-
-                result.AddIfNotNull(Construct(type, isUnboundGenericType, typeArguments));
             }
         }
 

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.ParameterSymbolKey.cs

@@ -3,7 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
-using System.Diagnostics;
 
 namespace Microsoft.CodeAnalysis;
 
@@ -69,6 +68,9 @@ protected sealed override SymbolKeyResolution Resolve(
                             Resolve(result, reader, metadataName, ordinal, delegateInvoke.Parameters);
                         }
 
+                        break;
+                    case INamedTypeSymbol { IsExtension: true, ExtensionParameter: { } extensionParameter }:
+                        Resolve(result, reader, metadataName, ordinal, [extensionParameter]);
                         break;
                 }
             }

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

@@ -49,6 +49,8 @@ public ImmutableArray<INamedTypeSymbol> AllInterfaces
 
     public bool IsExtension => false;
 
+    public IParameterSymbol ExtensionParameter => null;
+
     public static ImmutableArray<ITypeSymbol> TupleElementTypes => default;
 
     public static ImmutableArray<string> TupleElementNames => default;