improve the ident names and add comments for cases in pass_names macro

Author: sgasho

compiler/rustc_mir_transform/src/lib.rs

@@ -106,13 +106,15 @@ macro_rules! declare_passes {
 }
 
 macro_rules! pass_names {
-    ($mod_name:ident : $pass_name:ident { $($ident:ident),* $(,)? }) => {
+    // pass groups: only pass names inside are considered pass_names
+    ($mod_name:ident : $pass_group:ident { $($pass_name:ident),* $(,)? }) => {
         [
             $(
-                $mod_name::$pass_name::$ident.name(),
+                $mod_name::$pass_group::$pass_name.name(),
             )*
         ]
     };
+    // lone pass names: stringify the struct or enum name
     ($mod_name:ident : $pass_name:ident) => {
         [stringify!($pass_name)]
     };