require Reveal::All in normalize_erasing_regions

[lcnr]

would have caught a bug in mir inlining, see #77568 (comment)

[rust-highfive]

r? @oli-obk

(rust_highfive has picked a reviewer for you, use r? to override)

[oli-obk]

@bors r+ rollup

[bors]

📌 Commit 19e7095 has been approved by oli-obk

[JohnTitor]

Seems failed in #77797 (comment):

thread 'rustc' panicked at 'assertion failed: `(left == right)`
  left: `UserFacing`,
 right: `All`', /checkout/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:30:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.49.0-nightly (db0665ce8 2020-10-10) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z macro-backtrace -Z binary-dep-depinfo -Z force-unstable-if-unmarked -C opt-level=3 -C embed-bitcode=no -C codegen-units=1 -C debuginfo=0 -C debug-assertions=on -C overflow-checks=off -C link-args=-Wl,-rpath,$ORIGIN/../lib -C prefer-dynamic -C embed-bitcode=yes --crate-type lib

note: some of the compiler flags provided by cargo are hidden

[RUSTC-TIMING] core test:false 6.187
error: could not compile `core`

https://github.com/rust-lang-ci/rust/runs/1235982427

@bors r-

[matthewjasper]

There are a few places that should (sometimes) be given user facing param envs:

rust/compiler/rustc_lint/src/types.rs

Line 818 in 12187b7

let field_ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, field_ty);

rust/compiler/rustc_trait_selection/src/traits/structural_match.rs

Line 258 in 3e14b68

let ty = self.tcx().normalize_erasing_regions(ty::ParamEnv::empty(), field_ty);

rust/compiler/rustc_ty/src/needs_drop.rs

Lines 134 to 137 in 3e14b68

	let subst_ty = tcx.normalize_erasing_regions(
	self.param_env,
	required_ty.subst(tcx, substs),
	);

[lcnr]

doesn't normalize_erasing_regions ICE if it fails to normalize?

Will have to look into this a bit more deeply then

[matthewjasper]

It ICEs if an associated type projection isn't well-formed (i.e. the self type doesn't implement the trait that's expected), but doesn't if it does but can't be normalized.