Remove NullPointerException.

sdk/lib/_internal/compiler/implementation/ssa/optimize.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.
 
 part of ssa;
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
@@ skipping 733 matching lines @@
 class SsaDeadCodeEliminator extends HGraphVisitor implements OptimizationPhase {
   final HTypeMap types;
   final String name = "SsaDeadCodeEliminator";
 
   SsaDeadCodeEliminator(this.types);
 
   bool isDeadCode(HInstruction instruction) {
     return !instruction.hasSideEffects(types)
            && instruction.usedBy.isEmpty
            // A dynamic getter that has no side effect can still throw
-           // a NoSuchMethodError or a NullPointerException.
+           // a NoSuchMethodError.
            && instruction is !HInvokeDynamicGetter
            && instruction is !HCheck
            && instruction is !HTypeGuard
            && instruction is !HParameterValue
            && !instruction.isControlFlow();
   }
 
   void visitGraph(HGraph graph) {
     visitPostDominatorTree(graph);
   }
@@ skipping 589 matching lines @@
     }
 
     // For other fields having setters in the generative constructor body, set
     // the type to UNKNOWN to avoid relying on the type set in the initializer
     // list.
     allSetters.forEach((Element element) {
       backend.registerFieldConstructor(element, HType.UNKNOWN);
     });
   }
 }