TC does not properly resolve parse function

[PaulKlint]

import Exception;
import ParseTree;

syntax A = a: "a";

test bool tstA(){
    pt = parse(#A, "a");
    return a() := pt && pt is a;
}

gives

error("Could not instantiate type variables in type fun &T \<: Tree(type[&T \<: Tree], loc) with argument types (type[A],str)",|rascal:///experiments/Compiler/Examples/Tst.rsc|(327,14,<17,9>,<17,23>))
error("Function of type fun &T \<: Tree(type[&T \<: Tree], map[Production robust, list[CharRange] lookaheads], str, loc) cannot be called with argument types (type[A],str)",|rascal:///experiments/Compiler/Examples/Tst.rsc|(327,14,<17,9>,<17,23>))
error("Could not instantiate type variables in type fun &T \<: Tree(type[&T \<: Tree], str) with argument types (type[A],str)",|rascal:///experiments/Compiler/Examples/Tst.rsc|(327,14,<17,9>,<17,23>))
error("Name pt is not in scope",|rascal:///experiments/Compiler/Examples/Tst.rsc|(367,2,<18,24>,<18,26>))
error("Name pt is not in scope",|rascal:///experiments/Compiler/Examples/Tst.rsc|(361,2,<18,18>,<18,20>))
error("Function of type fun &T \<: Tree(type[&T \<: Tree], str, loc) cannot be called with argument types (type[A],str)",|rascal:///experiments/Compiler/Examples/Tst.rsc|(327,14,<17,9>,<17,23>))
|rascal://experiments::Compiler::Rascal2muRascal::RascalModule|(2652,25,<80,12>,<80,37>): "Module contains errors!"

[mahills]

This is most likely because Tree has a special status in the type system -- it is a normal ADT that also happens to be the supertype of all concrete syntax types.

[PaulKlint]

Do you see a solution for this?

[mahills]

I think I just need to call my own subtype function which checks this case first and then dispatches to the normal subtype function. I will work on it today.

[mahills]

This is now working. I added support for making Tree a supertype of all concrete syntax nonterminal types -- this was actually a fairly straightforward addition to ParseTree.rsc. Getting the rest of it working wasn't so straight-forward...