Support signed constants.

tests/compiler/dart2js/unparser_test.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.
 
 #import('dart:uri');
 #import('parser_helper.dart');
 #import("../../../lib/compiler/compiler.dart");
 #import("../../../lib/compiler/implementation/tree/tree.dart");
 
 testUnparse(String statement) {
@@ skipping 57 matching lines @@
 
   compile(
       scriptUri,
       fileUri('libraryRoot'),
       fileUri('packageRoot'),
       provider,
       handler,
       const ['--output-type=dart', '--unparse-validation']).then(continuation);
 }
 
+testSignedConstants() {
+  testUnparse('var x=+42;');
+  testUnparse('var x=+.42;');
+  testUnparse('var x=-42;');
+  testUnparse('var x=-.42;');
+  testUnparse('var x=+0;');
+  testUnparse('var x=+0.0;');
+  testUnparse('var x=+.0;');
+  testUnparse('var x=-0;');
+  testUnparse('var x=-0.0;');
+  testUnparse('var x=-.0;');
+}
+
 testGenericTypes() {
   testUnparse('var x=new List<List<int>>();');
   testUnparse('var x=new List<List<List<int>>>();');
   testUnparse('var x=new List<List<List<List<int>>>>();');
   testUnparse('var x=new List<List<List<List<List<int>>>>>();');
 }
 
 testForLoop() {
   testUnparse('for(;i<100;i++){}');
   testUnparse('for(i=0;i<100;i++){}');
@@ skipping 279 matching lines @@
   var expectedResult = @'topfoo(){}$topfoo(){var x=5;}A getA()=> null;'
       @'main(){var a=new A(); a.foo(); var b=new $A.fromFoo(); b.foo(); '
           @'var GREATVAR=b.myliba; b.mylist; a=getA(); $topfoo(); topfoo();}'
       @'class $A{$A.fromFoo(){}List<$A> mylist;num foo(){}A myliba;}'
       @'class A{foo(){}}';
   testDart2DartWithLibrary(mainSrc, librarySrc,
       (String result) { Expect.equals(expectedResult, result); });
 }
 
 main() {
+  testSignedConstants();
   testGenericTypes();
   testForLoop();
   testEmptyList();
   testClosure();
   testIndexedOperatorDecl();
   testNativeMethods();
   testPrefixIncrements();
   testConstModifier();
   testSimpleFileUnparse();
   testSimpleObjectInstantiation();
   testSimpleTopLevelClass();
   testClassWithSynthesizedConstructor();
   testClassWithMethod();
   testVariableDefinitions();
   testGetSet();
   testFactoryConstructor();
   testTopLevelField();
   testAbstractClass();
   testConflictLibraryClassRename();
   testNoConflictSendsRename();
   testConflictSendsRename();
 }