Create ParameterMirror.type lazily.

runtime/lib/mirrors.cc

Index: runtime/lib/mirrors.cc
diff --git a/runtime/lib/mirrors.cc b/runtime/lib/mirrors.cc
index ebd9517553d3085d1fbd4520d6e79d4ac9b4340c..d56bc320c5ee781c3a1255b44ad1840ca726c0cb 100644
--- a/runtime/lib/mirrors.cc
+++ b/runtime/lib/mirrors.cc
@@ -236,6 +236,7 @@ static Dart_Handle CreateLazyMirror(Dart_Handle target);
 
 
 static Dart_Handle CreateParameterMirrorList(Dart_Handle func) {
+  ASSERT(Dart_IsFunction(func));
   int64_t fixed_param_count;
   int64_t opt_param_count;
   Dart_Handle result = Dart_FunctionParameterCounts(func,
@@ -258,12 +259,9 @@ static Dart_Handle CreateParameterMirrorList(Dart_Handle func) {
   }
 
   for (int64_t i = 0; i < param_count; i++) {
-    Dart_Handle arg_type = Dart_FunctionParameterType(func, i);
-    if (Dart_IsError(arg_type)) {
-      return arg_type;
-    }
     Dart_Handle args[] = {
-      CreateLazyMirror(arg_type),
+      CreateMirrorReference(func),
+      Dart_NewInteger(i),
       Dart_NewBoolean(i >= fixed_param_count),  // optional param?
     };
     Dart_Handle param =
@@ -1918,4 +1916,14 @@ DEFINE_NATIVE_ENTRY(MethodMirror_return_type, 1) {
   return CreateTypeMirror(return_type);
 }
 
+
+DEFINE_NATIVE_ENTRY(ParameterMirror_type, 2) {
+  GET_NON_NULL_NATIVE_ARGUMENT(MirrorReference, ref, arguments->NativeArgAt(0));
+  GET_NON_NULL_NATIVE_ARGUMENT(Smi, pos, arguments->NativeArgAt(1));
+  const Function& func = Function::Handle(ref.GetFunctionReferent());
+  const AbstractType& param_type = AbstractType::Handle(func.ParameterTypeAt(
+      func.NumImplicitParameters() + pos.Value()));
+  return CreateTypeMirror(param_type);
+}
+
 }  // namespace dart