Rascal: get-annotation not supported on value, when clearly, there's a corresponding @lab annotation

Question

Here's the output from the console,

Debug print..
exprNode(
  assign(
    var(name(name("alpha")))[
      @at=|file:///Users/apil/Dropbox/Scripts/Class_Based_Analysis/SimpleClass_CopyObject.php|(56,6,<9,0>,<9,0>),
      @scope="scope"("","","",""),
      @decl=|php+variable:///alpha|,
      @phpdoc="",
      @lab=lab(3)
    ],
    new(
      name(name("MyClass")[
          @at=|file:///Users/apil/Dropbox/Scripts/Class_Based_Analysis/SimpleClass_CopyObject.php|(67,7,<9,0>,<9,0>),
          @scope="scope"("","","",""),
          @phpdoc=""
        ]),
      [])[
      @at=|file:///Users/apil/Dropbox/Scripts/Class_Based_Analysis/SimpleClass_CopyObject.php|(63,13,<9,0>,<9,0>),
      @scope="scope"("","","",""),
      @phpdoc="",
      @lab=lab(4)
    ])[
    @at=|file:///Users/apil/Dropbox/Scripts/Class_Based_Analysis/SimpleClass_CopyObject.php|(56,20,<9,0>,<9,0>),
    @scope="scope"("","","",""),
    @phpdoc="",
    @lab=lab(5)
  ],
  lab(5))[
  @lab=lab(5)
]
var(name(name("alpha")))[
  @at=|file:///Users/apil/Dropbox/Scripts/Class_Based_Analysis/SimpleClass_CopyObject.php|(56,6,<9,0>,<9,0>),
  @scope="scope"("","","",""),
  @decl=|php+variable:///alpha|,
  @phpdoc="",
  @lab=lab(3)
]
|rascal://soft::typing::php::elements::Identifier|(1678,6,<54,10>,<54,16>): get-annotation not supported on value at |rascal://soft::typing::php::elements::Identifier|(1678,6,<54,10>,<54,16>)
☞ Advice

and here's the script responsible for generating the content:

LabelToIdentifierMap mapp=( );
println("Debug print..");
iprintln(cfgNode);
result=[e | /assign(e,_):=cfgNode];

if(isEmpty(result))
    return mapp;

result=getElementFromSingletonList(result);
iprintln(result);
if(var(name(name(str x))):=result)
    mapp +=(result@lab:var(x));
else if(propertyFetch(var(name(name(str x))),name(name(str y))):=result)
    mapp +=(result@lab:propertySet(var(x),var(y)));
else
    throw "Unsupported expression encountered at left hand side of an assignment node.\n"+
    "Got: <result>. Error loc: 510142847";   
return mapp;

My concern is that the output of variable "result": var(name(name("alpha")))[ @at=... ] shows that there is an annotation @lab in the attached with the variable. Why am I unable to retrieve it? Also, how may I retrieve it if that's possible at all!

score 0 · Answer 1 · answered Jan 29 '15 at 19:55

The reason can be several things.

At least the language must know the type of the value you want to address the annotation on. Currently that type is value, which is not specific enough. I don't know why this is happening in your example because not all details are given. It could very well be that getElementFromSingletonList returns a value? I'd use result[0] or write a type parameterized function which returns the type of the element: &T get([&T elem]) = elem;
Annotations must be declared before they can be used, as in anno int MyExpressionType@lab; or anno int node@label;. This can only be done for the node type or defined data types.

So when the receiver of @ is typed well and the label of the annotation is declared, then it will work as expected:

 data MyExp = bla();
 anno int MyExp@label;
 MyExp example = bla()[@label=1];
 println(example@label); // prints 1

Thanks.. it makes sense. However, I do use a parameterized function to return the element from "getElementFromSingletonList(..)". This function ensures that the passed argument is a list with only a single element and throws an exception otherwise. I think this may fix the problem.. result=[e | /assign(Expr e,_):=cfgNode], as now the pattern is explicitly matched to an Expr type, for which the annotations are rightfully declared. Any thoughts?? — apil.tamang, Jan 29 '15 at 21:40
It would help to see the function signature, but if it's something like `value getElementFromSingletonList(list[value] l)` it would be better to have `&T getElementFromSingletonList(list[&T] l)` so it would maintain the type of the element. — Mark Hills, Jan 30 '15 at 12:24

Rascal: get-annotation not supported on value, when clearly, there's a corresponding @lab annotation

1 Answers1