Prevent MIRI ICE by bubbling up

[ouz-a]

This fixes MIRI ICE which resulted from this work.

r? @oli-obk

[RalfJung]

@bors try

Does this also fix the ICE in a local build with debug assertions? Or just the new ICE that started when #99383 landed?

[bors]

⌛ Trying commit 8b0690a with merge 4ef10657f99de0ed2da88f2ce0114812b9927fbf...

[ouz-a]

Does this also fix the ICE in a local build with debug assertions? Or just the new ICE that started when #99383 landed?

Only the new one, I would like to fix debug assertion one too but I don't know where to even begin with that.

[RalfJung]

Fair.^^

[compiler-errors]

If we end up landing this, I can put up a fix to change the debug assertion in a way that's not as risky as just removing it.

I'm gonna continue to see if we can revert the underlying root cause (the fact we currently don't normalize opaques with escaping bound vars).

[bors]

☀️ Try build successful - checks-actions
Build commit: 4ef10657f99de0ed2da88f2ce0114812b9927fbf (4ef10657f99de0ed2da88f2ce0114812b9927fbf)

[oli-obk]

If we end up landing this, I can put up a fix to change the debug assertion in a way that's not as risky as just removing it.

I'm gonna continue to see if we can revert the underlying root cause (the fact we currently don't normalize opaques with escaping bound vars).

do you want to keep trying or should we merge this PR now and you can work on a revert of it?

[compiler-errors]

Working on it in #100980, but I'm not sure how much of a perf improvement is needed to make it worth landing. If @RalfJung really needs this ICE to go away, then we can land this and I can work on top of a revert of this.

[RalfJung]

Well, a debug assertion that can actually be triggered is always a bug, and makes me worried about which things might break in later parts of the compiler due to the invariant violation. So it should probable at least become a regular assertion to ensure correct execution. And then it's still an ICE, which is a bug -- but it needs a nightly feature to be triggered. I also assume if it can be triggered in Miri there is some way to trigger it with rustc, though I don't know how.

I don't know of any real-life code that runs into this, though.

[compiler-errors]

Superseded by #100980 I think