Fix override completion inside records.

src/EditorFeatures/CSharpTest/Completion/CompletionProviders/OverrideCompletionProviderTests.cs

@@ -3042,5 +3042,25 @@ public override bool Bar(Baz baz)
 
             await VerifyCustomCommitProviderAsync(markupBeforeCommit, "Bar(NS2.Baz baz)", expectedCodeAfterCommit);
         }
+
+        [WpfFact, Trait(Traits.Feature, Traits.Features.Completion)]
+        public async Task OverrideInRecordWithoutExplicitOverriddenMember()
+        {
+            await VerifyItemExistsAsync(@"record Program
+{
+    override $$
+}", "ToString()");
+        }
+
+        [WpfFact, Trait(Traits.Feature, Traits.Features.Completion)]
+        public async Task OverrideInRecordWithExplicitOverriddenMember()
+        {
+            await VerifyItemIsAbsentAsync(@"record Program
+{
+    public override string ToString() => "";
+
+    override $$
+}", "ToString()");
+        }
     }
 }

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/INamedTypeSymbolExtensions.cs

@@ -584,10 +584,11 @@ private static bool IsOverridable(ISymbol member, INamedTypeSymbol containingTyp
             {
                 cancellationToken.ThrowIfCancellationRequested();
 
-                var overriddenMember = member.OverriddenMember();
-                if (overriddenMember != null)
+                if (!member.IsImplicitlyDeclared)
                 {
-                    result.Remove(overriddenMember);
+                    var overriddenMember = member.OverriddenMember();
+                    if (overriddenMember != null)
+                        result.Remove(overriddenMember);
                 }
             }
         }