anchor.diff:  HType potentialArray;
   HType potentialString;
   
  -void testUnion(Compiler compiler) {
  +void testUnion(MockCompiler compiler) {
     Expect.equals(CONFLICTING, 
                   CONFLICTING.union(CONFLICTING, compiler));
     Expect.equals(UNKNOWN, 
  
positive.code: // BSD-style license that can be found in the LICENSE file.
  
  #import("mock_compiler.dart");
  #source("../../../lib/compiler/implementation/ssa/types.dart");
  
  class DartType {
    const DartType(this.str);
    final String str;
  }
  
  const CONFLICTING = HType.CONFLICTING;
  const UNKNOWN = HType.UNKNOWN;
  
negative.code:                 FIXED_ARRAY.union(FIXED_ARRAY, compiler));
  }
  
  void testIntersection(MockCompiler compiler) {
    Expect.equals(CONFLICTING, 
                  CONFLICTING.intersection(CONFLICTING, compiler));
    Expect.equals(CONFLICTING, 
  