Handle creating ParameterMirrors for the parameters of forwarding constructors.

runtime/lib/mirrors.cc

Index: runtime/lib/mirrors.cc
diff --git a/runtime/lib/mirrors.cc b/runtime/lib/mirrors.cc
index d2427f9b4122ef421af9c4fe58f9f01cbbbe7ed1..3a3d4dce69ecb2390447e156e8e3f91119573867 100644
--- a/runtime/lib/mirrors.cc
+++ b/runtime/lib/mirrors.cc
@@ -129,11 +129,19 @@ static RawInstance* CreateParameterMirrorList(const Function& func,
   const Array& results = Array::Handle(Array::New(non_implicit_param_count));
   const Array& args = Array::Handle(Array::New(9));
 
-  // Return for synthetic functions and getters.
-  if (func.IsGetterFunction() ||
-      func.IsImplicitConstructor() ||
-      func.IsImplicitGetterFunction() ||
-      func.IsImplicitSetterFunction()) {
+  if (func.IsForwardingConstructor()) {
+    // Forwarding constructors for mixin applications don't have any source to
+    // parse, but they do have parameters. Use the names/types/metadata from
+    // constructor that we are forwarding to. We will probably have to revisit
+    // this when restrictions on constructors in mixins are relaxed.
+    const Function& target = Function::Handle(func.ForwardingTarget());
+    ASSERT(!target.IsNull());
+    return CreateParameterMirrorList(target, owner_mirror);
+  }
+
+  if (func.IsGetterFunction() || func.IsImplicitConstructor()) {
+    // These have no parameters.
+    ASSERT(results.Length() == 0);
     return results.raw();
   }