Fix for dartbug.com/6036: the intersection of two different types is not always conflicting.

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 381 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)) &&
-        leftType.intersection(rightType).isConflicting()) {
+        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 69 matching lines @@
     // [visitInvokeBinary], which are visited by invoking the [super]'s
     // visit method.
     return super.visitEquals(node);
   }
 
   HInstruction visitTypeGuard(HTypeGuard node) {
     HInstruction value = node.guarded;
     // If the intersection of the types is still the incoming type then
     // the incoming type was a subtype of the guarded type, and no check
     // is required.
-    HType combinedType = types[value].intersection(node.guardedType);
+    HType combinedType = types[value].intersection(node.guardedType, compiler);
     return (combinedType == types[value]) ? value : node;
   }
 
   HInstruction visitIs(HIs node) {
     DartType type = node.typeExpression;
     Element element = type.element;
     if (identical(element.kind, ElementKind.TYPE_VARIABLE)) {
       compiler.unimplemented("visitIs for type variables");
     }
 
@@ skipping 66 matching lines @@
   HInstruction visitTypeConversion(HTypeConversion node) {
     HInstruction value = node.inputs[0];
     DartType type = types[node].computeType(compiler);
     if (identical(type.element, compiler.dynamicClass)
         || identical(type.element, compiler.objectClass)) {
       return value;
     }
     if (types[value].canBeNull() && node.isBooleanConversionCheck) {
       return node;
     }
-    HType combinedType = types[value].intersection(types[node]);
+    HType combinedType = types[value].intersection(types[node], compiler);
     return (combinedType == types[value]) ? value : node;
   }
 
   Element findConcreteFieldForDynamicAccess(HInstruction receiver,
                                             Selector selector) {
     HType receiverType = types[receiver];
     if (!receiverType.isUseful()) return null;
     if (receiverType.canBeNull()) return null;
     DartType type = receiverType.computeType(compiler);
     if (type == null) return null;
@@ skipping 659 matching lines @@
           new Map.from(blockFieldSetters[block.predecessors[0]]);
       // Loop headers are the only nodes with back edges.
       if (!block.isLoopHeader()) {
         for (int i = 1; i < block.predecessors.length; i++) {
           Map<Element, HType> predecessorsFieldSetters =
               blockFieldSetters[block.predecessors[i]];
           Map<Element, HType> newFieldSetters = new Map<Element, HType>();
           predecessorsFieldSetters.forEach((Element element, HType type) {
             HType currentType = currentFieldSetters[element];
             if (currentType != null) {
-              newFieldSetters[element] = currentType.union(type);
+              newFieldSetters[element] =
+                  currentType.union(type, backend.compiler);
             }
           });
           currentFieldSetters = newFieldSetters;
         }
       } else {
         assert(block.predecessors.length <= 2);
       }
     }
     block.forEachPhi((HPhi phi) => phi.accept(this));
     block.forEachInstruction(
@@ skipping 69 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);
     });
   }
 }