Move `MirPass` to `rustc_mir_transform`.

Because that's now the only crate that uses it.

Moving stuff out of `rustc_middle` is always welcome.

I chose to use `impl crate::MirPass`/`impl crate::MirLint` (with
explicit `crate::`) everywhere because that's the only mention of
`MirPass`/`MirLint` used in all of these files. (Prior to this change,
`MirPass` was mostly imported via `use rustc_middle::mir::*` items.)

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/rustc_mir_transform/src/jump_threading.rs b/compiler/rustc_mir_transform/src/jump_threading.rs
index 435b6a01163..02dd56e1b4f 100644
--- a/compiler/rustc_mir_transform/src/jump_threading.rs
+++ b/compiler/rustc_mir_transform/src/jump_threading.rs
@@ -61,7 +61,7 @@ const MAX_BACKTRACK: usize = 5;
 const MAX_COST: usize = 100;
 const MAX_PLACES: usize = 100;
 
-impl<'tcx> MirPass<'tcx> for JumpThreading {
+impl<'tcx> crate::MirPass<'tcx> for JumpThreading {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
         sess.mir_opt_level() >= 2
     }