Work around clippy bug in const-checking

I really hate having to do this, since I don't think unstable compiler
APIs should have to work around misuse by external crates. However, this
is the only way this change will pass CI without a ton of modifications
to clippy and/or involvement of the clippy team.

compiler/rustc_mir/src/transform/check_consts/qualifs.rs

@@ -244,8 +244,11 @@ where
     };
 
     // Check the qualifs of the value of `const` items.
-    if let ty::ConstKind::Unevaluated(def, _, promoted) = constant.literal.val {
-        assert!(promoted.is_none());
+    if let ty::ConstKind::Unevaluated(def, _, _promoted) = constant.literal.val {
+        // FIXME(rust-lang/rust-clippy#6080): Const-checking should never see promoteds, but clippy
+        // is broken.
+        // assert!(promoted.is_none());
+
         // Don't peek inside trait associated constants.
         if cx.tcx.trait_of_item(def.did).is_none() {
             let qualifs = if let Some((did, param_did)) = def.as_const_arg() {