Improve the error message on the wrong usage of super in class methods

[e-kayrakli]

Starting simple:

class C {
  proc init() {
    init this;
    writeln(super.x);
  }
}

var c = new C();

results in error: unresolved call 'RootClass.x'. I don't think we should be exposing RootClass (no, we should). A class that doesn't inherit anything explicitly should not be able to use super. If there's some meaning to RootClass that should be exposed to the user, I still think this error message could be better. #26051 looks thematically related.

The related real-world case might be hairier. What's the meaning of super in a method that's implemented in an inner module? Reading the docs, I think, in the context of modules, super can only be used to find other modules and not variables within them. But my real-world attempt was:

module superTest {
  var x = 10;

  module Inner {
    class C {
      var myX: int;

      proc init() {
        this.myX = super.x; // I wanted this to be `superTest.x` 
      }
    }
  }

  import this.Inner;

  proc main() {
    var c = new Inner.C();
  }
}

But looks like I had to use superTest in the inner module first. I kind of wished super to look also into the parent module, but I understand that it can get complicated with actual inheritance at play. This may be a case for --detailed-errors or a hint in the error message that super can only be used to access superclass(es)'s fields/methods and not module-scope variables.

[bradcray]

I don't think we should be exposing RootClass.

We definitely do, and did so intentionally:

• https://chapel-lang.org/docs/language/spec/classes.html#the-root-class
• Rename object root class? #20414
  [sample rationale: I want to write a well-typed routine that specifies that it can take any class, so constrain the argument to : RootClass].

Given that, I don't think the error message is particularly bad, but also wouldn't object to improving it further.

What's the meaning of super in a method that's implemented in an inner module?

I believe that, outside of a class/record/method, super can only be used in import statements (and maybe use, though I'm having trouble coming up with a working example)? E.g., see this example.

(this error message could also stand to be improved since it doesn't mention the potential to use super in import/use).

[e-kayrakli]

Thanks, I wasn't aware (or not remembering) that discussion. I agree with that rationale. I linked to your comment in the OP.

I still wish for a better error message, though.