Test monotonicity of expression typings.

src/types.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_TYPES_H_
 #define V8_TYPES_H_
 
 #include "src/conversions.h"
 #include "src/factory.h"
 #include "src/handles.h"
@@ skipping 224 matching lines @@
  *
  * Otherwise:
  *
  *   ON         OSS             US         OU32     ON
  * ______[_______________[_______________[_______[_______
  *     -2^31             0              2^31    2^32
  *
  *
  * E.g., OtherUnsigned32 (OU32) covers all integers from 2^31 to 2^32-1.
  *
+ * NOTE: OtherSigned32 (OS32) and OU31 (OtherUnsigned31) are empty if SMIs are
+ *       32-bit wide.  They should thus never be used directly, only indirectly
+ *       via e.g. Number.
  */
 
 #define PROPER_BITSET_TYPE_LIST(V) \
   REPRESENTATION_BITSET_TYPE_LIST(V) \
   SEMANTIC_BITSET_TYPE_LIST(V)
 
 #define BITSET_TYPE_LIST(V) \
   MASK_BITSET_TYPE_LIST(V) \
   PROPER_BITSET_TYPE_LIST(V)
 
@@ skipping 786 matching lines @@
   bool Narrows(BoundsImpl that) {
     return that.lower->Is(this->lower) && this->upper->Is(that.upper);
   }
 };
 
 typedef BoundsImpl<ZoneTypeConfig> Bounds;
 
 } }  // namespace v8::internal
 
 #endif  // V8_TYPES_H_