[dart2js] Assign the correct type to super tearoffs.

Bug: dart-lang/sdk#40902
Fixes: dart-lang/sdk#40902
Change-Id: Ie2c58e5dab9902cbabd7c2ef9aae5b6c1773c7e7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138663
Reviewed-by: Stephen Adams <[email protected]>

Author: fishythefish

pkg/compiler/lib/src/ssa/builder_kernel.dart

@@ -5248,7 +5248,8 @@ class KernelSsaGraphBuilder extends ir.Visitor {
     inputs.addAll(arguments);
 
     AbstractValue typeMask;
-    if (target is FunctionEntity) {
+    if (selector.isGetter && target.isGetter ||
+        !selector.isGetter && target is FunctionEntity) {
       typeMask = _typeInferenceMap.getReturnTypeOf(target);
     } else {
       typeMask = _abstractValueDomain.dynamicType;

tests/compiler/dart2js_extra/40902_test.dart

@@ -0,0 +1,19 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "package:expect/expect.dart";
+
+class Foo {
+  int f() => 42;
+}
+
+class Bar extends Foo {
+  void test() {
+    Expect.isFalse(super.f is int);
+  }
+}
+
+void main() {
+  Bar().test();
+}