Auto merge of #103808 - cjgillot:vec-cache, r=TaKO8Ki

Use an IndexVec to cache queries with index-like key

Revival of an old idea. Let's see if it has more effect.

r? `@ghost`

compiler/rustc_middle/src/query/mod.rs

@@ -7,6 +7,9 @@
 use crate::ty::{self, print::describe_as_module, TyCtxt};
 use rustc_span::def_id::LOCAL_CRATE;
 
+mod keys;
+pub use keys::Key;
+
 // Each of these queries corresponds to a function pointer field in the
 // `Providers` struct for requesting a value of that type, and a method
 // on `tcx: TyCtxt` (and `tcx.at(span)`) for doing that request in a way