Fix some editor warnings.

lib/compiler/implementation/ssa/variable_allocator.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.
 
 /**
  * The [LiveRange] class covers a range where an instruction is live.
  */
 class LiveRange {
   final int start;
   // [end] is not final because it can be updated due to loops.
@@ skipping 11 matching lines @@
  */
 class LiveInterval {
   /**
    * The id where there instruction is defined.
    */
   int start;
   final List<LiveRange> ranges;
   LiveInterval() : ranges = <LiveRange>[];
 
   /**
-   * Update all ranges that are contained in [start, end[ to
-   * die at [end].
+   * Update all ranges that are contained in [from, to[ to
+   * die at [to].
    */
-  void loopUpdate(int start, int end) {
+  void loopUpdate(int from, int to) {
     for (LiveRange range in ranges) {
-      if (start <= range.start && range.end < end) {
-        range.end = end;
+      if (from <= range.start && range.end < to) {
+        range.end = to;
       }
     }
   }
 
   /**
    * Add a new range to this interval.
    */
   void add(LiveRange interval) {
     ranges.add(interval);
   }
@@ skipping 385 matching lines @@
   String allocateName(HInstruction instruction) {
     String name;
     if (instruction is HCheck) {
       // Special case the check instruction to use the name of its
       // checked instruction.
       HCheck check = instruction;
       name = names.ownName[check.checkedInput];
       // If the name is null, then the checked input is being
       // generated at use site, and we don't need a name for the check
       // instruction.
-      if (name == null) return;
+      if (name == null) return null;
     } else if (instruction is HParameterValue) {
       HParameterValue parameter = instruction;
       name = parameterNames[parameter.element];
       if (name == null) {
         name = allocateWithHint(parameter.element.name.slowToString());
       }
     } else if (instruction.sourceElement !== null) {
       name = allocateWithHint(instruction.sourceElement.name.slowToString());
     } else {
       // We could not find an element for the instruction. If the
@@ skipping 116 matching lines @@
       if (!needsName(input)) {
         names.addAssignment(predecessor, input, phi);
       } else {
         names.addCopy(predecessor, input, phi);
       }
     }
 
     namer.allocateName(phi);
   }
 }