Support argument definition test operator (issue 4264)

compiler/java/com/google/dart/compiler/parser/DartParser.java

Index: compiler/java/com/google/dart/compiler/parser/DartParser.java
===================================================================
--- compiler/java/com/google/dart/compiler/parser/DartParser.java	(revision 11387)
+++ compiler/java/com/google/dart/compiler/parser/DartParser.java	(working copy)
@@ -3426,12 +3426,22 @@
       case STRING_LAST_SEGMENT:
         throw new StringInterpolationParseError();
 
+      case CONDITIONAL:
+        return parseArgumentDefinitionTest();
+
       default: {
         return parseLiteral();
       }
     }
   }
 
+  private DartExpression parseArgumentDefinitionTest() {
+    beginArgumentDefinitionTest();
+    int operatorOffset = position();
+    expect(Token.CONDITIONAL);
+    return done(new DartUnaryExpression(Token.CONDITIONAL, operatorOffset, parseIdentifier(), true));
+  }
+
   private DartExpression parseConstructorInvocation(boolean isConst) {
     List<DartTypeNode> parts = new ArrayList<DartTypeNode>();
     beginConstructor();