nll insufficiently checks wf bounds

[lcnr]

#![feature(nll)]

trait Trait {
    const ASSOC: usize;
}

struct Foo<'a, 'b: 'a>(&'a &'b ());
impl<'a, 'b> Trait for Foo<'a, 'b> {
    const ASSOC: usize = 3;
}
fn foo<'a, 'b>() -> usize {
    <Foo<'a, 'b> as Trait>::ASSOC
}

should error because 'b: 'a is not met but needed by Foo<'a, 'b>::ASSOC.
This happens because the predicates of constants are only checked for function definitions
while they have to also get checked for associated constants. I feel like we should really
just check the predicates for all constants instead of trying to safe some work here.

rust/compiler/rustc_borrowck/src/type_check/mod.rs

Lines 466 to 473 in d2df372

	if let ty::FnDef(def_id, substs) = *constant.literal.ty().kind() {
	let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, substs);
	self.cx.normalize_and_prove_instantiated_predicates(
	def_id,
	instantiated_predicates,
	location.to_locations(),
	);
	}

[compiler-errors]

We seem to enforce this now.

[compiler-errors]

Presumably #120019