Support checked mode for return type.

lib/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 380 matching lines @@
   }
 
   HInstruction handleIdentityCheck(HInvokeBinary node) {
     HInstruction left = node.left;
     HInstruction right = node.right;
     HType leftType = types[left];
     HType rightType = types[right];
     assert(!leftType.isConflicting() && !rightType.isConflicting());
 
     // We don't optimize on numbers to preserve the runtime semantics.
-    if (!(left.isNumber(types) && right.isNumber(types)) &&
+    if (!(left.isNumberOrNull(types) && right.isNumberOrNull(types)) &&
         leftType.intersection(rightType, compiler).isConflicting()) {
       return graph.addConstantBool(false, constantSystem);
     }
 
     if (left.isConstantBoolean() && right.isBoolean(types)) {
       HConstant constant = left;
       if (constant.constant.isTrue()) {
         return right;
       } else {
         return new HNot(right);
@@ skipping 201 matching lines @@
     return result;
   }
 
   HInstruction visitInvokeDynamicSetter(HInvokeDynamicSetter node) {
     Element field =
         findConcreteFieldForDynamicAccess(node.receiver, node.selector);
     if (field == null || !field.isAssignable()) return node;
     HInstruction value = node.inputs[1];
     if (compiler.enableTypeAssertions) {
       HInstruction other = value.convertType(
-          compiler, field, HTypeConversion.CHECKED_MODE_CHECK);
+          compiler,
+          field.computeType(compiler),
+          HTypeConversion.CHECKED_MODE_CHECK);
       if (other != value) {
         node.block.addBefore(node, other);
         value = other;
       }
     }
     return new HFieldSet(field, node.inputs[0], value);
   }
 
   HInstruction visitStringConcat(HStringConcat node) {
     DartString folded = const LiteralDartString("");
@@ skipping 711 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);
     });
   }
 }