Merge pull request #45594 from CyrusNajmabadi/gotoDefNullable

Fix issue preventing going to def on a complicated metadata symbol involving nullability and generics

src/EditorFeatures/CSharpTest/SymbolKey/SymbolKeyTests.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// 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.Linq;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.SymbolId
+{
+    [UseExportProvider]
+    public class SymbolKeyTests
+    {
+        [Fact, WorkItem(45437, "https://github.com/dotnet/roslyn/issues/45437")]
+        public async Task TestGenericsAndNullability()
+        {
+            var typeSource = @"
+#nullable enable
+
+    public sealed class ConditionalWeakTableTest<TKey, TValue> /*: IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable*/
+        where TKey : class
+        where TValue : class
+    {
+        public ConditionalWeakTable() { }
+        public void Add(TKey key, TValue value) { }
+        public void AddOrUpdate(TKey key, TValue value) { }
+        public void Clear() { }
+        public TValue GetOrCreateValue(TKey key) => default;
+        public TValue GetValue(TKey key, ConditionalWeakTableTest<TKey, TValue>.CreateValueCallback createValueCallback) => default;
+        public bool Remove(TKey key) => false;
+
+        public delegate TValue CreateValueCallback(TKey key);
+    }".Replace("<", "&lt;").Replace(">", "&gt;");
+
+            var workspaceXml = @$"
+<Workspace>
+    <Project Language=""C#"">
+        <CompilationOptions Nullable=""Enable""/>
+        <Document FilePath=""C.cs"">
+{typeSource}
+        </Document>
+    </Project>
+</Workspace>
+";
+            using var workspace = TestWorkspace.Create(workspaceXml);
+
+            var solution = workspace.CurrentSolution;
+            var project = solution.Projects.Single();
+
+            var compilation = await project.GetCompilationAsync();
+
+            var type = compilation.GetTypeByMetadataName("ConditionalWeakTableTest`2");
+            var method = type.GetMembers("GetValue").OfType<IMethodSymbol>().Single();
+            var callbackParamater = method.Parameters[1];
+            var parameterType = callbackParamater.Type;
+            Assert.Equal("global::ConditionalWeakTableTest<TKey!, TValue!>.CreateValueCallback!", parameterType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat.WithMiscellaneousOptions(SymbolDisplayMiscellaneousOptions.IncludeNotNullableReferenceTypeModifier)));
+
+            var symbolKey = SymbolKey.Create(method);
+            var resolved = symbolKey.Resolve(compilation).Symbol;
+
+            Assert.Equal(method, resolved);
+        }
+    }
+}

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.EquivalenceVisitor.cs

@@ -344,8 +344,7 @@ private bool HandleNamedTypesWorker(INamedTypeSymbol x, INamedTypeSymbol y, Dict
             {
                 Debug.Assert(GetTypeKind(x) == GetTypeKind(y));
 
-                if (x.IsDefinition != y.IsDefinition ||
-                    IsConstructedFromSelf(x) != IsConstructedFromSelf(y) ||
+                if (IsConstructedFromSelf(x) != IsConstructedFromSelf(y) ||
                     x.Arity != y.Arity ||
                     x.Name != y.Name ||
                     x.IsAnonymousType != y.IsAnonymousType ||