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

runtime/lib/object.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/bootstrap_natives.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/code_patcher.h"
 #include "vm/exceptions.h"
 #include "vm/heap.h"
@@ skipping 342 matching lines @@
 
 
 DEFINE_NATIVE_ENTRY(Internal_inquireIs64Bit, 0) {
 #if defined(ARCH_IS_64_BIT)
   return Bool::True().raw();
 #else
   return Bool::False().raw();
 #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