Adding a comment

src/Workspaces/CSharp/Portable/LanguageServices/CSharpTypeInferenceService.TypeInferrer.cs

@@ -1777,7 +1777,8 @@ private IEnumerable<TypeInferenceInfo> InferTypeInYieldStatement(YieldStatementS
                 var memberSymbol = GetDeclaredMemberSymbolFromOriginalSemanticModel(declaration);
 
                 var memberType = GetMemberType(memberSymbol, out _);
-
+                // We don't care what the type is, as long as it has 1 type argument. This will work for IEnumerable, IEnumerator,
+                // IAsyncEnumerable, IAsyncEnumerator and it's also good for error recovery in case there is a missing using.
                 return memberType is INamedTypeSymbol namedType && namedType.TypeArguments.Length == 1
                     ? SpecializedCollections.SingletonEnumerable(new TypeInferenceInfo(namedType.TypeArguments[0]))
                     : SpecializedCollections.EmptyEnumerable<TypeInferenceInfo>();