Create an error message for recursive short class definitions

[Martin Sjölund]

{{{class Env

type Env = Real;

end Env;

class A

type Env = Env.Env;
Env e = 1.0;

end A;}}}

Env will lookup itself.

[Martin Sjölund]

Something to have a look at if you're bored. Should be easy to solve.

[AlexeyLebedev]

In Inst.instClassdef2, the cases with SCode.DERIVED start with calls to removeSelfReference. Do I understand correctly that, even though self-reference is possible in CLASS_EXTENDS definitions,

a) DERIVED correspond to short definitions (like in this example), and, thus,

b) there must be no self-reference in them?

[Martin Sjölund]

Yes. There should be no self-references in (any) class definitions. Short or otherwise (else the compiler loops).

[AlexeyLebedev]

Cases like
{{{class A
extends A.A;

class A

Real x;

end A;

end A;}}}

seem to work fine. Should they also be forbidden?

[Martin Sjölund]

That's allowed; it's not referencing itself.

[AlexeyLebedev]

Sorry, what do you mean by self-reference, then?

I used it in the same sense as it is used in the function Inst.removeSelfReference: defining a class className in terms of class className.otherClassName . As I understand, this is OK in extends statements, but not in short class definitions?

[Martin Sjölund]

A self-reference is if lookup of an identifier results in the same class you are trying to instantiate.
For example, class A extends A; end A; results in stack overflow, but should probably generate an error message (or be fixed; one could guard each InstExtends from extending each class more than once by sending it a list). Stack overflow is never acceptable.
Note that type Env = Env.Env; would probably not be possible to fix in this way, as it does not have a class to begin with. So this self-reference needs to be broken.

[AlexeyLebedev]

Added a check and a new error message in revision 7279.