fixes #27586, prefer context type in generic inference

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

Index: pkg/dev_compiler/lib/src/compiler/code_generator.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/code_generator.dart b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
index 0bbe9eda8bd685d6c47e487e2875426a733a2048..d3501bdadad28f1694ba23cce0b8bc3809e76fcf 100644
--- a/pkg/dev_compiler/lib/src/compiler/code_generator.dart
+++ b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
@@ -5362,7 +5362,8 @@ class CodeGenerator extends GeneralizingAstVisitor
     return result is JS.Node ? annotate(result, node) : result;
   }
 
-  List/*<T>*/ _visitList/*<T extends AstNode>*/(Iterable/*<T>*/ nodes) {
+  // TODO(jmesserly): we should make sure this only returns JS AST nodes.
+  List/*<T>*/ _visitList/*<T>*/(Iterable nodes) {

[vsm, 2016/11/30 04:05:33]

Why was this change needed?

[Jennifer Messerly, 2016/11/30 04:35:04]

the type was completely wrong before. It's mixing up Dart AST nodes and JS AST
nodes. The return type definitely is not the same as the input type. Possibly we
could have two generic types T and R.

To be honest, DDC has some typing sloppiness in what its visit methods do, it
would be great to clean up at some point.

     if (nodes == null) return null;
     var result = /*<T>*/ [];
     for (var node in nodes) result.add(_visit(node) as dynamic/*=T*/);