Rollup merge of #149664 - Kivooeo:infallible-type-unreachable-code, r=davidtwco

attempt to fix unreachable code regression

For some reason it works, it checks function output type and suppress warning if type is uninhabited

~~This double negations in code breaks my mind actually~~

I'd love to revisit this part in future and try to find a proper solution maybe, but for now I feel like it's enough before release to fix the issue? I really wonder what team does think, especially `@cjgillot` and other people who are more confident in this part of compiler than I do

I tried a lot of things here, it's only approach that pass all tests included new regression one

fixes rust-lang/rust#149571

r? compiler

Author: matthiaskrgr