Normalize before erasing late-bound regions in `equal_up_to_regions`
Normalize erasing regions **first**, before passing the type through a `BottomUpFolder` which erases late-bound regions too.
The root cause of this issue is due to 96d4137dee, which removes a `normalize_erasing_regions` that happens before this call to `equal_up_to_regions`. While reverting that commit might be a fix, I think it was suspicious to be erasing late-bound regions first _then_ normalizing types in the first place in `equal_up_to_regions`.
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I am tempted to ask the reviewer to review and `r+` this without a UI test, since the existing issues that I think this fixes are all incredibly difficult to minimize (anything hyper/warp related, given the nature of those libraries 😓) or impossible to reproduce locally (the miri test), namely:
* This recently reported issue with tokio + warp: #101430
* This issue from `@RalfJung` about Miri being broken: #101344
* This additional issue reported in a comment by `@tmandry` (issue with fuchsia + hyper): https://github.com/rust-lang/rust/issues/101344#issuecomment-1235974564
I have locally verified that the repro in #101430 is fixed with this PR, but after a couple of hours of attempting to minimize this error and either failing to actually repro the ICE, or being overwhelmed with the number of traits and functions I need to inline into a UI test, I have basically given up. Thoughts are appreciated on how best to handle this.
r? `@oli-obk` who is at the intersection of MIR and types-related stuff who may be able to give advice 😅
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