Fix most warnings and other minor cleanups.

lib/compiler/implementation/ssa/codegen.dart

Index: lib/compiler/implementation/ssa/codegen.dart
diff --git a/lib/compiler/implementation/ssa/codegen.dart b/lib/compiler/implementation/ssa/codegen.dart
index d155f0d0b0691a4f8ac058706af24f8f8c941500..cadc8e80ec5f02faa7274ff90e81c9bbeb647681 100644
--- a/lib/compiler/implementation/ssa/codegen.dart
+++ b/lib/compiler/implementation/ssa/codegen.dart
@@ -501,10 +501,12 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
       return false;
     }
 
+    HBinaryArithmetic binary = instruction;
+    assert(binary.inputs.length == 3);
     // Is it a builtin operation involving constant numbers?
-    if (instruction.builtin && instruction.inputs.length == 3) {
-      var left = instruction.inputs[1];
-      var right = instruction.inputs[2];
+    if (binary.builtin) {
+      var left = binary.left;
+      var right = binary.right;
       if (left.isConstantNumber() && isCommutative) {
         var tmp = right;
         right = left;
@@ -513,18 +515,20 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
         return false;
       }
       // Right is constant number.
-      var value = right.constant.value;
+      HConstant constantRight = right;
+      NumConstant numberConstant = constantRight.constant;
+      num value = numberConstant.value;
       // Check that left has the same name as the definition and emit
       // the short update definition if it is.
       if (variableNames.getName(left) == name) {
-        if (instruction is HAdd && right.constant.value == 1) {
+        if (binary is HAdd && value == 1) {
           buffer.add('++');
           declareVariable(name);
-        } else if (instruction is HSubtract && right.constant.value == 1) {
+        } else if (binary is HSubtract && value == 1) {
           buffer.add('--');
           declareVariable(name);
         } else {
-          var operation = instruction.operation.name;
+          var operation = binary.operation.name;
           declareVariable(name);
           buffer.add(' ${operation}= ${value}');
         }
@@ -2481,8 +2485,8 @@ class SsaOptimizedCodeGenerator extends SsaCodeGenerator {
   void bailout(HTypeGuard guard, String reason) {
     if (maxBailoutParameters === null) {
       maxBailoutParameters = 0;
-      work.guards.forEach((HTypeGuard guard) {
-        int inputLength = guard.inputs.length;
+      work.guards.forEach((HTypeGuard workGuard) {
+        int inputLength = workGuard.inputs.length;
         if (inputLength > maxBailoutParameters) {
           maxBailoutParameters = inputLength;
         }