Support reflectClass on parameterized classes

pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart

Index: pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart b/pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart
index cb46e8892fe93206a8c4039082df70af341ce65c..3abbfb173de35fcb0b677fc64b8377bbee859b32 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart
@@ -311,12 +311,22 @@ class JsClosureMirror extends JsInstanceMirror implements ClosureMirror {
   }
 }
 
+// For generic classes, mirrors uses the same representation, [ClassMirror],
+// for the instantiated and uninstantiated type.  Somewhat awkwardly, most APIs
+// (e.g., [newInstance]) treat the uninstantiated type as if instantiated
+// with all dynamic.  The representation below is correspondingly a bit wonky.
+// For an uninstantiated generic class, [_cls] is the instantiated type (with
+// dynamic) and [_raw] is null.  For an instantiated generic class, [_cls] is
+// the instantiated type (with the corresponding type parameters), and [_raw]
+// is the generic factory.
 class JsClassMirror extends JsMirror implements ClassMirror {
   final Type _cls;
   final Symbol simpleName;
-  // Generic class factory
+  // Generic class factory for instantiated types.
   final dynamic _raw;
 
+  ClassMirror _originalDeclaration;
+
   // TODO(vsm): Do this properly
   ClassMirror _mixin = null;
   List<TypeMirror> _typeArguments;
@@ -414,11 +424,8 @@ class JsClassMirror extends JsMirror implements ClassMirror {
     return _declarations;
   }
 
-  JsClassMirror._(Type cls)
-      : _cls = cls,
-        _raw = _getGenericClass(_unwrap(cls)),
-        simpleName = new Symbol(JS('String', '#.name', _unwrap(cls))) {
-    var typeArgs = _getGenericArgs(_unwrap(cls));
+  void _initialize() {
+    var typeArgs = _getGenericArgs(_unwrap(_cls));
     if (typeArgs == null) {
       _typeArguments = const [];
     } else {
@@ -427,6 +434,20 @@ class JsClassMirror extends JsMirror implements ClassMirror {
     }
   }
 
+  JsClassMirror._(Type cls)
+      : _cls = cls,
+        _raw = _getGenericClass(_unwrap(cls)),
+        simpleName = new Symbol(JS('String', '#.name', _unwrap(cls))) {
+    _initialize();
+  }
+
+  JsClassMirror._uninstantiated(Type cls)
+      : _cls = cls,
+        _raw = null,

[Bob Nystrom, 2017/05/25 20:16:05]

There's some duplication between these. Maybe a single constructor like:

JsClassMirror._(Type cls, {bool instantiated = true})
    : _cls = cls,
      _raw = instantiated ? _getGenericClass(_unwrap(cls)) : null,
      simpleName = new Symbol(JS('String', '#.name', _unwrap(cls))) {
  _initialize();
}

[vsm, 2017/05/25 20:26:52]

That is cleaner.  :-)  

Done and re-inlined initialize as well.

+        simpleName = new Symbol(JS('String', '#.name', _unwrap(cls))) {
+    _initialize();
+  }
+
   InstanceMirror newInstance(Symbol constructorName, List args,
       [Map<Symbol, dynamic> namedArgs]) {
     // TODO(vsm): Support factory constructors and named arguments.
@@ -490,8 +511,12 @@ class JsClassMirror extends JsMirror implements ClassMirror {
     if (_raw == null) {
       return this;
     }
-    throw new UnimplementedError(
-        "ClassMirror.originalDeclaration unimplemented");
+    if (_originalDeclaration != null) {
+      return _originalDeclaration;
+    }
+    _originalDeclaration =
+        new JsClassMirror._uninstantiated(_wrap(JS('', '#()', _raw)));
+    return _originalDeclaration;
   }
 
   ClassMirror get superclass {