restrict generic function type subtyping

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 bf898e0e6a951804cfef9e06697f9c7beceb6c1c..32a12a59ae540f02077b3229773710ac3fe008d0 100644
--- a/pkg/analyzer/lib/src/dart/element/type.dart
+++ b/pkg/analyzer/lib/src/dart/element/type.dart
@@ -1026,16 +1026,12 @@ class FunctionTypeImpl extends TypeImpl implements FunctionType {
     // This type cast is safe, because we checked it above.
     FunctionType s = other as FunctionType;
     if (t.typeFormals.isNotEmpty) {
-      if (s.typeFormals.isEmpty) {
-        t = instantiateToBounds(t);
-      } else {
-        List<DartType> freshVariables = relateTypeFormals(t, s, returnRelation);
-        if (freshVariables == null) {
-          return false;
-        }
-        t = t.instantiate(freshVariables);
-        s = s.instantiate(freshVariables);
+      List<DartType> freshVariables = relateTypeFormals(t, s, returnRelation);
+      if (freshVariables == null) {
+        return false;
       }
+      t = t.instantiate(freshVariables);
+      s = s.instantiate(freshVariables);
     } else if (s.typeFormals.isNotEmpty) {
       return false;
     }