Handle local variable declarations without immediate assignment.

tests/compiler/dart2js/cpa_inference_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 "package:expect/expect.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/scanner/scannerlib.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/source_file.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/types/types.dart';
 
 import "parser_helper.dart";
@@ skipping 175 matching lines @@
   final String source = r"""
     main () {
       var x = "__dynamic_for_test";
       x;
     }
     """;
   AnalysisResult result = analyze(source);
   result.checkNodeHasUnknownType('x');
 }
 
+testVariableDeclaration() {
+  final String source = r"""
+      main() {
+        var v1;
+        var v2;
+        v2 = 1;
+        v1; v2;
+      }
+      """;
+  AnalysisResult result = analyze(source);
+  result.checkNodeHasType('v1', [result.nullType]);
+  result.checkNodeHasType('v2', [result.int]);
+}
+
 testLiterals() {
   final String source = r"""
       main() {
         var v1 = 42;
         var v2 = 42.0;
         var v3 = 'abc';
         var v4 = true;
         var v5 = null;
         v1; v2; v3; v4; v5;
       }
@@ skipping 1128 matching lines @@
           xy.rawType, foo)).simplify(result.compiler),
       new TypeMask.nonNullSubclass(bc.rawType));
 
   Selector bar = new Selector.call(buildSourceString("bar"), null, 0);
 
   Expect.isNull(inferredType(bar));
 }
 
 void main() {
   testDynamicBackDoor();
+  testVariableDeclaration();
   testLiterals();
   testRedefinition();
   testIfThenElse();
   testTernaryIf();
   testWhile();
   testFor1();
   testFor2();
   testFor3();
   testToplevelVariable();
   testNonRecusiveFunction();
@@ skipping 30 matching lines @@
   testListWithCapacity();
   testEmptyList();
   testJsCall();
   testIsCheck();
   testSeenClasses();
   testGoodGuys();
   testIntDoubleNum();
   testConcreteTypeToTypeMask();
   testSelectors();
 }