fix #30912, record scope dependencies on unused typedef type arguments

Change-Id: Ic859620fb4ff7f9965b46849aa96eb74dfe59ccb
Reviewed-on: https://dart-review.googlesource.com/9125
Reviewed-by: Vijay Menon <[email protected]>

Author: Jennifer Messerly

pkg/dev_compiler/lib/src/compiler/type_utilities.dart

@@ -16,6 +16,11 @@ Set<TypeParameterElement> freeTypeParameters(DartType t) {
     if (t is TypeParameterType) {
       result.add(t.element);
     } else if (t is FunctionType) {
+      // Visit type arguments of typedefs, because we use these when we're
+      // emitting the type.
+      if (t.name != '' && t.name != null) {
+        t.typeArguments.forEach(find);
+      }
       find(t.returnType);
       t.parameters.forEach((p) => find(p.type));
       t.typeFormals.forEach((p) => find(p.bound));

tests/language_strong/function_type_alias10_test.dart

@@ -0,0 +1,23 @@
+// Copyright (c) 2017, 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 {}
+
+class Bar {}
+
+typedef Type Func<S extends Foo, T>(T s);
+
+class Baz<S extends Foo, T extends Bar> {
+  Func<S, Bar> func;
+}
+
+/// Regression test for https://github.com/dart-lang/sdk/issues/30912
+void main() {
+  dynamic baz = new Baz();
+  Expect.isNull(baz.func);
+  baz.func = (Bar b) => b.runtimeType;
+  Expect.equals(baz.func(new Bar()), Bar);
+}