Avoid use of NonConstantValue in SSA

pkg/compiler/lib/src/ssa/nodes.dart

 // 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.
 
 import '../closure.dart';
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../dart_types.dart';
@@ skipping 180 matching lines @@
     HBasicBlock result = addNewBlock();
     result.loopInformation = new HLoopInformation(result, target, labels);
     return result;
   }
 
   HConstant addConstant(ConstantValue constant, Compiler compiler,
       {SourceInformation sourceInformation}) {
     HConstant result = constants[constant];
     // TODO(johnniwinther): Support source information per constant reference.
     if (result == null) {
+      if (!constant.isConstant) {
+        // We use `null` as the value for invalid constant expressions.
+        constant = const NullConstantValue();
+      }
       TypeMask type = computeTypeMask(compiler, constant);
       result = new HConstant.internal(constant, type)
         ..sourceInformation = sourceInformation;
       entry.addAtExit(result);
       constants[constant] = result;
     } else if (result.block == null) {
       // The constant was not used anymore.
       entry.addAtExit(result);
     }
     return result;
@@ skipping 3061 matching lines @@
 class HDynamicType extends HRuntimeType {
   HDynamicType(DynamicType dartType, TypeMask instructionType)
       : super(const <HInstruction>[], dartType, instructionType);
 
   accept(HVisitor visitor) => visitor.visitDynamicType(this);
 
   int typeCode() => HInstruction.DYNAMIC_TYPE_TYPECODE;
 
   bool typeEquals(HInstruction other) => other is HDynamicType;
 }