Use computeConstantValue instead of constantValue

pkg/dev_compiler/lib/src/compiler/code_generator.dart

 // Copyright (c) 2015, 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 'dart:collection' show HashMap, HashSet;
 import 'dart:math' show min, max;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 4430 matching lines @@
   int _asIntInRange(Expression expr, int low, int high) {
     expr = expr.unParenthesized;
     if (expr is IntegerLiteral) {
       if (expr.value >= low && expr.value <= high) return expr.value;
       return null;
     }
     int finishIdentifier(SimpleIdentifier identifier) {
       Element staticElement = identifier.staticElement;
       if (staticElement is PropertyAccessorElement && staticElement.isGetter) {
         PropertyInducingElement variable = staticElement.variable;
-        int value = variable?.constantValue?.toIntValue();
+        int value = variable?.computeConstantValue()?.toIntValue();
         if (value != null && value >= low && value <= high) return value;
       }
       return null;
     }
 
     if (expr is SimpleIdentifier) {
       return finishIdentifier(expr);
     } else if (expr is PrefixedIdentifier && !expr.isDeferred) {
       return finishIdentifier(expr.identifier);
     }
@@ skipping 1428 matching lines @@
   if (targetIdentifier.staticElement is! PrefixElement) return false;
   var prefix = targetIdentifier.staticElement as PrefixElement;
 
   // The library the prefix is referring to must come from a deferred import.
   var containingLibrary = resolutionMap
       .elementDeclaredByCompilationUnit(target.root as CompilationUnit)
       .library;
   var imports = containingLibrary.getImportsWithPrefix(prefix);
   return imports.length == 1 && imports[0].isDeferred;
 }