Refactor/idx as fun

[leissa]

.Idx is now a constant of type .Nat -> *.

Unfortunately, the prec-magic in the output is pretty broken. For this reason, I needed to port a lot of tests from (.Idx 123) to .Idx 123.

Rmark: We should really fix the prec magic before adding more and more test cases Oo
(see #97)

[leissa]

Maybe this fixes #95

[leissa]

I also finally refactored:

• type_int_ -> type_int
• lit_int_ -> lit_int

So, I hope you have ported your branches in the meantime :)

[NeuralCoder3]

I needed to port a lot of tests from (.Idx 123) to .Idx 123.

This seems odd. Additional parentheses should not make a program invalid.
Especially since these parentheses are usually needed in other contexts in thorin (as opposed to other functional languages (Haskell, coq, OCaml, ...) where they are commonly omitted).

[leissa]

I needed to port a lot of tests from (.Idx 123) to .Idx 123.

This seems odd. Additional parentheses should not make a program invalid. Especially since these parentheses are usually needed in other contexts in thorin (as opposed to other functional languages (Haskell, coq, OCaml, ...) where they are commonly omitted).

No, I needed to port the CHECK-DAG part not the actual test case.

[NeuralCoder3]

Looks good.