emit 'this.x' when 'super.x' accesses a field

lib/src/compiler/code_generator.dart

Index: lib/src/compiler/code_generator.dart
diff --git a/lib/src/compiler/code_generator.dart b/lib/src/compiler/code_generator.dart
index ca56b1f7938fadaa362d2916ea0bc13415cc0d81..008a106236b5122ebd93efdf7955e06376bcf4d3 100644
--- a/lib/src/compiler/code_generator.dart
+++ b/lib/src/compiler/code_generator.dart
@@ -3054,6 +3054,15 @@ class CodeGenerator extends GeneralizingAstVisitor
       return js.call('dart.dload(#, #)', [_visit(target), name]);
     }
 
+    if (target is SuperExpression &&
+        member is FieldElement &&
+        member.getter.isSynthetic &&
+        member.setter.isSynthetic) {

[Jennifer Messerly, 2016/04/18 21:10:12]

Oops I didn't reply fast enough to the original thread :)
Here's what I was going to say in reply to Vijay:

I think the idea is that a field will always has an implied getter. We have
read-only fields (final int x = ...) but not write-only fields :). So checking
the getter is safe.

So the old code LGTM but not the new code :). I don't think a setter is
guaranteed to be there if you have a final field? Either way would be good to
add a test for it.

if it helps I can poke around in Analyzer and see if they have a better way of
seeing what is an "actual field". I'm a little worried if the `isSynthetic` bit
is reliable or if the check is necessary. But maybe it is.

[Jennifer Messerly, 2016/04/18 21:20:13]

Ah, so you should be able to just check `!member.isSynthetic` -- in other words,
check that the field itself is not synthetic. My grepping through Analyzer
(specifically pkg/analyzer/lib/src/dart/element/builder.dart) leads me to
believe that should work :)

[Harry Terkelsen, 2016/04/18 21:28:58]

On final fields, setter is null. I'll just check if member is synthetic per your
suggestion. I also added a test.

+      // If super.x is actually a field, then x is an instance property since
+      // subclasses cannot override x.
+      return js.call('this.#', [name]);
+    }
+
     String code;
     if (member != null && member is MethodElement && !isStatic) {
       // Tear-off methods: explicitly bind it.