var should implement function_like directly

[frenchy64]

var should implement callable directly.

TODO is here

jank/compiler+runtime/src/cpp/jank/runtime/behavior/callable.cpp

Line 712 in 7ecc570

/* TODO: Move call fns into var so we can remove these checks. */

function_like is here:

jank/compiler+runtime/include/cpp/jank/runtime/behavior/callable.hpp

Line 201 in 7ecc570

concept function_like = requires(T * const t) {

[jeaye]

We're not using function_like right now. We inherit from callable and override the fns. The main reason is that inheritance grants us default behavior for all arities we don't care about. That default behavior throws an arity exception. By using a concept for this, we'd need to have every callable implement every arity. Most of them would just throw the arity exception anyway.

I have a local TODO that we might be able to use CRTP with callable so that virtual dispatch is not required. This would require some exploration, though.

[frenchy64]

Ah thanks. I wasn't seeing the full picture.