fixes #28236, generic methods should not cause warnings in Dart 1

pkg/analyzer/lib/src/dart/element/type.dart

Index: pkg/analyzer/lib/src/dart/element/type.dart
diff --git a/pkg/analyzer/lib/src/dart/element/type.dart b/pkg/analyzer/lib/src/dart/element/type.dart
index 58932c67539f040f586fbae66425e1e7ab8c7e09..968c18fa1a85581e1382e38008800b7220269c93 100644
--- a/pkg/analyzer/lib/src/dart/element/type.dart
+++ b/pkg/analyzer/lib/src/dart/element/type.dart
@@ -833,11 +833,12 @@ class FunctionTypeImpl extends TypeImpl implements FunctionType {
 
   @override
   bool isSubtypeOf(DartType type) {
+    var typeSystem = new TypeSystemImpl(null);
     return relate(
-        this,
-        type,
+        typeSystem.instantiateToBounds(this),
+        typeSystem.instantiateToBounds(type),
         (DartType t, DartType s, _, __) => t.isAssignableTo(s),
-        new TypeSystemImpl(null).instantiateToBounds);
+        typeSystem.instantiateToBounds);
   }
 
   @override