Check for a passed-in type argument vector in the prolog of generic functions.

runtime/lib/object.cc

Index: runtime/lib/object.cc
diff --git a/runtime/lib/object.cc b/runtime/lib/object.cc
index c6490c76f71de81de2bdccae094491046d1ddaa1..139fb4631d1f0bb67b3571e97124a68b2d8654c7 100644
--- a/runtime/lib/object.cc
+++ b/runtime/lib/object.cc
@@ -360,4 +360,35 @@ DEFINE_NATIVE_ENTRY(Internal_inquireIs64Bit, 0) {
 #endif  // defined(ARCH_IS_64_BIT)
 }
 
+
+DEFINE_NATIVE_ENTRY(Internal_prependTypeArguments, 3) {
+  const TypeArguments& function_type_arguments =
+      TypeArguments::CheckedHandle(zone, arguments->NativeArgAt(0));
+  const TypeArguments& parent_type_arguments =
+      TypeArguments::CheckedHandle(zone, arguments->NativeArgAt(1));
+  if (function_type_arguments.IsNull() && parent_type_arguments.IsNull()) {
+    return TypeArguments::null();
+  }
+  GET_NON_NULL_NATIVE_ARGUMENT(Smi, smi_len, arguments->NativeArgAt(2));
+  const intptr_t len = smi_len.Value();
+  const TypeArguments& result =
+      TypeArguments::Handle(zone, TypeArguments::New(len, Heap::kOld));

[rmacnak, 2017/06/20 17:20:46]

Maybe kNew? With repeated calls of the of same generic closure, only the first
type will become the canonical type and the rest will just grow old space.
Similar to what we did for Object.runtimeType.

[regis, 2017/06/21 04:39:03]

Done.

+  AbstractType& type = AbstractType::Handle(zone);
+  const intptr_t split = parent_type_arguments.IsNull()
+                             ? len - function_type_arguments.Length()
+                             : parent_type_arguments.Length();
+  for (intptr_t i = 0; i < split; i++) {
+    type = parent_type_arguments.IsNull() ? Type::DynamicType()
+                                          : parent_type_arguments.TypeAt(i);
+    result.SetTypeAt(i, type);
+  }
+  for (intptr_t i = split; i < len; i++) {
+    type = function_type_arguments.IsNull()
+               ? Type::DynamicType()
+               : function_type_arguments.TypeAt(i - split);
+    result.SetTypeAt(i, type);
+  }
+  return result.Canonicalize();
+}
+
 }  // namespace dart