Inline type check where type argument that we check against is instantiated.

runtime/vm/code_generator.cc

 // Copyright (c) 2012, 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/code_generator.h"
 
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
@@ skipping 376 matching lines @@
   // inlined assembly.
   if (!type.IsInstantiated()) return;
   // TODO(srdjan): Implement assembly code for checking type arguments then
   // remove this check.
   if (Class::Handle(type.type_class()).HasTypeArguments()) {
     const AbstractTypeArguments& type_arguments =
         AbstractTypeArguments::Handle(type.arguments());
     const bool is_raw_type = type_arguments.IsNull() ||
         type_arguments.IsRaw(type_arguments.Length());
     if (!is_raw_type) {
-      return;
+      // We cannot inline tests for instances with more than one type argument
+      // or if its class has not been resolved (malformed type).
+      if (type_arguments.Length() != 1) {
+        // We can handle only one argument so far.
+        return;
+      }
+      const AbstractType& tp_argument =
+          AbstractType::ZoneHandle(type_arguments.TypeAt(0));
+      if (!tp_argument.IsType()) {
+        // E.g, it is TypeParameter.
+        return;
+      }
+      const Type& list_type =
+          Type::Handle(Isolate::Current()->object_store()->list_interface());
+      Error& malformed_error = Error::Handle();
+      if (!list_type.IsSubtypeOf(type, &malformed_error)) {
+        return;
+      }
+      // The type argument at index 0 must be instantiated and not malformed.
+      // A malformed type would have caused a type error earlier.
+      ASSERT(tp_argument.HasResolvedTypeClass());
     }
   }
   DartFrameIterator iterator;
   StackFrame* caller_frame = iterator.NextFrame();
   ASSERT(caller_frame != NULL);
   const Code& code = Code::Handle(caller_frame->LookupDartCode());
   ASSERT(!code.IsNull());
   uword loc = code.GetTypeTestAtNodeId(node_id);
   if (loc != 0) {
     // Found type test cache.
@@ skipping 1058 matching lines @@
       }
     }
   }
   // The cache is null terminated, therefore the loop above should never
   // terminate by itself.
   UNREACHABLE();
   return Code::null();
 }
 
 }  // namespace dart