Extract rustc_hir out of rustc

[Centril]

The new crate contains:

pub mod def;
pub mod def_id;
mod hir;
pub mod hir_id;
pub mod itemlikevisit;
pub mod pat_util;
pub mod print;
mod stable_hash_impls;

pub use hir::*;
pub use hir_id::*;
pub use stable_hash_impls::HashStableContext;

Remains to be done in follow-up PRs:

• Move rustc::hir::map into rustc_hir_map -- this has to be a separate crate due to the dep_graph (blocked on Move the dep_graph construction to a dedicated crate. #67761).

• Move references to rustc::hir to rustc_hir where possible.

cc #65031

r? @Zoxc

[Zoxc]

I think it would be better to have a is_ignored_attr method on syntax::HashStableContext and move the impl to syntax.

[Centril]

This doesn't work out well unfortunately. I'm only able to move one of the impls, but not the impl<AstCtx: crate::HashStableContext> HashStable<AstCtx> for [ast::Attribute] { one because it becomes orphaned (including with specialization). So I would prefer to have those impls in one place and this file is the only way to do that I think.

[Zoxc]

You could add with_node_id_hashing_mode and while_hashing_hir_bodies to rustc_hir::HashStableContext then you wouldn't need to keep all the impls here.

[Zoxc]

@bors r+ p=5 rollup=never

[bors]

📌 Commit cdf32e1 has been approved by Zoxc

[bors]

⌛ Testing commit cdf32e1 with merge 7494250...

[bors]

☀️ Test successful - checks-azure
Approved by: Zoxc
Pushing 7494250 to master...