Introduce {ConstantElementsPair} struct for type safety.

src/compiler/types.cc

 // 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.
 
 #include <iomanip>
 
 #include "src/compiler/types.h"
 
 #include "src/handles-inl.h"
 #include "src/ostreams.h"
@@ skipping 309 matching lines @@
     case PROMISE_RESOLVE_THENABLE_JOB_INFO_TYPE:
     case PROMISE_REACTION_JOB_INFO_TYPE:
     case DEBUG_INFO_TYPE:
     case BREAK_POINT_INFO_TYPE:
     case CELL_TYPE:
     case WEAK_CELL_TYPE:
     case PROTOTYPE_INFO_TYPE:
     case TUPLE2_TYPE:
     case TUPLE3_TYPE:
     case CONTEXT_EXTENSION_TYPE:
+    case CONSTANT_ELEMENTS_PAIR_TYPE:
       UNREACHABLE();
       return kNone;
   }
   UNREACHABLE();
   return kNone;
 }
 
 Type::bitset BitsetType::Lub(i::Object* value) {
   DisallowHeapAllocation no_allocation;
   if (value->IsNumber()) {
@@ skipping 722 matching lines @@
   return i::SmiValuesAre31Bits() ? kSigned31 : kSigned32;
 }
 
 BitsetType::bitset BitsetType::UnsignedSmall() {
   return i::SmiValuesAre31Bits() ? kUnsigned30 : kUnsigned31;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8