bounded_unknown_function.chr

:- module(bounded_unknown_function, [result/1]).
:- use_module(library(prelude)).

% A constraint, not a function. The renamer accepts the name in the
% requiring clause (constraints and functions share the symbol
% namespace), but the resolver detects that the bound's target is
% not a function and emits unknown_bound_function.
:- chr_constraint result(any), foo(int, int).

:- function pick(T, T) -> T requiring foo(T, T) -> bool.

pick(X, _) -> X.

result(R) <=> R is pick(1, 2).