Auto merge of #74802 - Mark-Simulacrum:reland-74069, r=nnethercote

Reland #74069

Investigation in #74716 has concluded that this PR is indeed not a regression (and in fact the rollup itself is not either).

This reverts the revert in #74611.

r? @nnethercote cc @eddyb

diff --cc src/librustc_middle/lib.rs
Simple merge

diff --cc src/librustc_middle/ty/layout.rs
Simple merge