Report use of malbounded interface in type test.

runtime/vm/exceptions.cc

Index: runtime/vm/exceptions.cc
===================================================================
--- runtime/vm/exceptions.cc	(revision 28940)
+++ runtime/vm/exceptions.cc	(working copy)
@@ -491,15 +491,17 @@
 
 
 // Allocate, initialize, and throw a TypeError or CastError.
+// If bound_error is not null, throw a TypeError, even for a type cast.
 void Exceptions::CreateAndThrowTypeError(intptr_t location,
                                          const String& src_type_name,
                                          const String& dst_type_name,
                                          const String& dst_name,
-                                         const String& malformed_error) {
+                                         const String& bound_error) {
   const Array& args = Array::Handle(Array::New(7));
 
   ExceptionType exception_type =
-      dst_name.Equals(kCastErrorDstName) ? kCast : kType;
+      (bound_error.IsNull() && dst_name.Equals(kCastErrorDstName)) ?
+          kCast : kType;
 
   DartFrameIterator iterator;
   const Script& script = Script::Handle(GetCallerScript(&iterator));
@@ -510,17 +512,17 @@
   args.SetAt(1, Smi::Handle(Smi::New(line)));
   args.SetAt(2, Smi::Handle(Smi::New(column)));
 
-  // Initialize '_srcType', '_dstType', '_dstName', and '_malformedError'.
+  // Initialize '_srcType', '_dstType', '_dstName', and '_boundError'.
   args.SetAt(3, src_type_name);
   args.SetAt(4, dst_type_name);
   args.SetAt(5, dst_name);
-  args.SetAt(6, malformed_error);
+  args.SetAt(6, bound_error);
 
   // Type errors in the core library may be difficult to diagnose.
   // Print type error information before throwing the error when debugging.
   if (FLAG_print_stacktrace_at_throw) {
-    if (!malformed_error.IsNull()) {
-      OS::Print("%s\n", malformed_error.ToCString());
+    if (!bound_error.IsNull()) {
+      OS::Print("%s\n", bound_error.ToCString());
     }
     intptr_t line, column;
     script.GetTokenLocation(location, &line, &column);
@@ -532,7 +534,7 @@
                 dst_type_name.ToCString(),
                 dst_name.ToCString());
     } else {
-      OS::Print("malformed type used.\n");
+      OS::Print("malbounded type used.\n");
     }
   }
   // Throw TypeError or CastError instance.