Cleanup some EarlyBinder::skip_binder() -> EarlyBinder::subst_identity()

[kylematsuda]

fix some incorrect skip_binder()'s as identified in #112006 (review)

r? @compiler-errors @lcnr @jackh726

(hope it's alright to just tag everyone who commented 😅)

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[kylematsuda]

There are some skip_binder lower down in this function too. Should those be subst_identity as well?

[compiler-errors]

Yeah I believe so

[kylematsuda]

thanks, just updated the commit to add those 👍

[kylematsuda]

I remember a similar pattern in Instance::subst_mir that I used skip_binder for previously:

rust/compiler/rustc_middle/src/ty/instance.rs

Lines 581 to 591 in a9baa16

	pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: EarlyBinder<&T>) -> T
	where
	T: TypeFoldable<TyCtxt<'tcx>> + Copy,
	{
	let v = v.map_bound(|v| *v);
	if let Some(substs) = self.substs_for_mir_body() {
	v.subst(tcx, substs)
	} else {
	v.skip_binder()
	}
	}

Should that one also be subst_identity()?

[compiler-errors]

Yes, probably

[compiler-errors]

@rustbot author

[compiler-errors]

@bors r+ rollup

[bors]

📌 Commit 57cbe25 has been approved by compiler-errors

It is now in the queue for this repository.