With the change on how we allocate names on HCheck instructions, I need to adjust slightly how we r…

dart/lib/compiler/implementation/ssa/codegen.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.
 
 class SsaCodeGeneratorTask extends CompilerTask {
   final JavaScriptBackend backend;
   SsaCodeGeneratorTask(JavaScriptBackend backend)
       : this.backend = backend,
         super(backend.compiler);
   String get name() => 'SSA code generator';
@@ skipping 2500 matching lines @@
     addIndented('}\n');  // Close 'switch'.
     setup.add('  }\n');
   }
 
   bool visitAndOrInfo(HAndOrBlockInformation info) => false;
   bool visitIfInfo(HIfBlockInformation info) => false;
   bool visitLoopInfo(HLoopBlockInformation info) => false;
   bool visitTryInfo(HTryBlockInformation info) => false;
   bool visitSequenceInfo(HStatementSequenceInformation info) => false;
 
-  // For instructions that reference a guard or a check, we change that 
-  // reference to the instruction they guard against. Therefore, we must        
-  // use that instruction when restoring the environment.       
+  // If argument is a [HCheck] and it does not have a name, we try to
+  // find the name of its checked input. Note that there must be a
+  // name, otherwise the instruction would not be in the live
+  // environment.
   HInstruction unwrap(argument) {       
-    while (argument is HCheck) argument = argument.checkedInput;        
+    while (argument is HCheck && !variableNames.hasName(argument)) {
+      argument = argument.checkedInput;
+    }
+    assert(variableNames.hasName(argument));
     return argument;    
   }
 
   void visitTypeGuard(HTypeGuard node) {
     indent--;
     addIndented('case ${node.state}:\n');
     indent++;
     addIndented('state = 0;\n');
 
     setup.add('    case ${node.state}:\n');
@@ skipping 152 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
     if (labeledBlockInfo.body.start.hasGuards()) {
       endBailoutSwitch();
     }
   }
 }