Some preparations for directly computing the ICH of crate-metadata.

[michaelwoerister]

This PR contains some small fixes in preparation for direct metadata hashing. It mostly just moves stuff into places where it will be needed (making the module structure slightly cleaner along the way) and it fixes some omissions in the MIR region eraser.

r? @nikomatsakis

[nikomatsakis]

Nit: can you add a blank line in the {} block? This formatting makes it hard to see that the arms are a distinct group from the line below.

[nikomatsakis]

I feel like this is a classic case where it'd be good to enumerate the Rvalue variants (so that if a new variant is added, or a variant changes, we are likely to notice this case)

[nikomatsakis]

r=me if the match is made exhaustive

[michaelwoerister]

@bors r=nikomatsakis

[bors]

📌 Commit 00fed35 has been approved by nikomatsakis

[bors]

🔒 Merge conflict

[bstrie]

There's a submodule conflict causing some mass PR invalidations, but rebasing reveals many other conflicts which I don't feel comfortable fixing myself (I already feel dirty enough rebasing commits in other people's repos...).

[bstrie]

@bors r=nikomatsakis

[bors]

📌 Commit c9a61b1 has been approved by nikomatsakis

[michaelwoerister]

@bors r=nikomatsakis

Rebased

[bors]

📌 Commit 45deab4 has been approved by nikomatsakis