Introduce a flag --limit-ints-to-64-bits in the VM in order to investigate the

runtime/lib/integers.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/bootstrap_natives.h"
 
 #include "include/dart_api.h"
 #include "vm/dart_entry.h"
 #include "vm/dart_api_impl.h"
 #include "vm/exceptions.h"
@@ skipping 391 matching lines @@
 }
 
 
 DEFINE_NATIVE_ENTRY(Bigint_getDigits, 1) {
   const Bigint& bigint = Bigint::CheckedHandle(arguments->NativeArgAt(0));
   return bigint.digits();
 }
 
 
 DEFINE_NATIVE_ENTRY(Bigint_allocate, 4) {
+  if (FLAG_limit_ints_to_64_bits) {
+    // The allocated Bigint value is not necessarily out of range, but it may
+    // be used as an operand in an operation resulting in a Bigint.
+    Exceptions::ThrowRangeErrorMsg(
+        "Integer operand requires conversion to Bigint");
+  }
   // First arg is null type arguments, since class Bigint is not parameterized.
   const Bool& neg = Bool::CheckedHandle(arguments->NativeArgAt(1));
   const Smi& used = Smi::CheckedHandle(arguments->NativeArgAt(2));
   const TypedData& digits = TypedData::CheckedHandle(arguments->NativeArgAt(3));
   ASSERT(!digits.IsNull());
   return Bigint::New(neg.value(), used.Value(), digits);
 }
 
 }  // namespace dart