If the projection is InProgress on the projection cache while normalizing, return that same type.

[ereslibre]

This avoids an overflow under certain conditions on the compiler.

Fixes: #34260
Fixes: #47032

[rust-highfive]

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[eddyb]

r? @nikomatsakis

[ereslibre]

I don't know if other work was ongoing to fix this in a different way (or more structurally) than this patch. I will nevertheless have a look at the failing tests.

[nikomatsakis]

@ereslibre thanks for the PR; it does seem this is triggering an ICE for some reason. That said, we are currently engaged in an effort to basically rewrite this code and our approach to normalization as part of the Traits Working Group. To be honest, I am inclined to avoid changing the projection code for now and instead pursue "lazy normalization", unless this fixes a dire issue for you. Would you be interested in helping with that effort instead?

[ereslibre]

@nikomatsakis it's fine, not a dire issue :) Thank you so much for the great pointers, will have a look at them!