Support the optional path operator (?.), which is the replacement

of the optional path operator (->) used in Classic Groovy.
For an example,

  class Person {
      String name
      int age
  }

  Person x = new Person(name:"Foo", age:25)
  assert x.name == "Foo"
  assert x?.name == "Foo"

  x = null
  assert x?.name == null
  // assert x->name == null  for the case of Classic Groovy


git-svn-id: http://svn.codehaus.org/groovy/trunk/groovy/groovy-core@1974 a5544e8c-8a19-0410-ba12-f9af4593a198

src/main/org/codehaus/groovy/antlr/AntlrParserPlugin.java

@@ -876,8 +876,6 @@ protected Expression expressionSwitch(AST node) {
                 return ternaryExpression(node);
 
             case OPTIONAL_ARG:
-                return binaryExpression(Types.NAVIGATE, node);
-
             case DOT:
                 return dotExpression(node);
 
@@ -1292,7 +1290,7 @@ protected Expression dotExpression(AST node) {
                     return new AttributeExpression(leftExpression, field);
                 }
                 String property = identifier(identifierNode);
-                return new PropertyExpression(leftExpression, property);
+                return new PropertyExpression(leftExpression, property, node.getType()==OPTIONAL_ARG);
             }
         }
         return methodCallExpression(node);