Attach type info to extension method and object method tear-offs

lib/src/codegen/js_codegen.dart

Index: lib/src/codegen/js_codegen.dart
diff --git a/lib/src/codegen/js_codegen.dart b/lib/src/codegen/js_codegen.dart
index bb73a3cb104db8624875837fc86061c2952b312c..80e21de15f17c33ce2ff5dc7e77304955f9cf7cd 100644
--- a/lib/src/codegen/js_codegen.dart
+++ b/lib/src/codegen/js_codegen.dart
@@ -2456,9 +2456,10 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
     String code;
     if (member != null && member is MethodElement && !isStatic) {
       // Tear-off methods: explicitly bind it.
-      // TODO(leafp): Attach runtime types to these static tearoffs
       if (_requiresStaticDispatch(target, memberId.name)) {
-        return js.call('dart.#.bind(#)', [name, _visit(target)]);
+        var type = member.type;
+        var clos = js.call('dart.#.bind(#)', [name, _visit(target)]);
+        return js.call('dart.fn(#, #)', [clos, _emitFunctionTypeParts(type)]);
       }
       code = 'dart.bind(#, #)';
     } else if (_requiresStaticDispatch(target, memberId.name)) {