MirPass: make name more const

compiler/rustc_middle/src/lib.rs

@@ -30,6 +30,7 @@
 #![feature(assert_matches)]
 #![feature(box_patterns)]
 #![feature(core_intrinsics)]
+#![feature(const_type_name)]
 #![feature(discriminant_kind)]
 #![feature(exhaustive_patterns)]
 #![feature(coroutines)]

compiler/rustc_middle/src/mir/mod.rs

@@ -140,8 +140,21 @@ fn to_profiler_name(type_name: &'static str) -> &'static str {
 /// loop that goes over each available MIR and applies `run_pass`.
 pub trait MirPass<'tcx> {
     fn name(&self) -> &'static str {
-        let name = std::any::type_name::<Self>();
-        if let Some((_, tail)) = name.rsplit_once(':') { tail } else { name }
+        // FIXME Simplify the implementation once more `str` methods get const-stable.
+        // See copypaste in `MirLint`
+        const {
+            let name = std::any::type_name::<Self>();
+            let bytes = name.as_bytes();
+            let mut i = bytes.len();
+            while i > 0 && bytes[i - 1] != b':' {
+                i = i - 1;
+            }
+            let (_, bytes) = bytes.split_at(i);
+            match std::str::from_utf8(bytes) {
+                Ok(name) => name,
+                Err(_) => name,
+            }
+        }
     }
 
     fn profiler_name(&self) -> &'static str {

compiler/rustc_mir_transform/src/pass_manager.rs

@@ -8,6 +8,7 @@ use crate::{lint::lint_body, validate, MirPass};
 pub trait MirLint<'tcx> {
     fn name(&self) -> &'static str {
         // FIXME Simplify the implementation once more `str` methods get const-stable.
+        // See copypaste in `MirPass`
         const {
             let name = std::any::type_name::<Self>();
             let bytes = name.as_bytes();