ensure we intern all promoteds as InternKind::Promoted

Author: RalfJung

compiler/rustc_mir/src/const_eval/eval_queries.rs

@@ -59,16 +59,13 @@ fn eval_body_using_ecx<'mir, 'tcx>(
     ecx.run()?;
 
     // Intern the result
-    // FIXME: since the DefId of a promoted is the DefId of its owner, this
-    // means that promoteds in statics are actually interned like statics!
-    // However, this is also currently crucial because we promote mutable
-    // non-empty slices in statics to extend their lifetime, and this
-    // ensures that they are put into a mutable allocation.
-    // For other kinds of promoteds in statics (like array initializers), this is rather silly.
-    let intern_kind = match tcx.static_mutability(cid.instance.def_id()) {
-        Some(m) => InternKind::Static(m),
-        None if cid.promoted.is_some() => InternKind::Promoted,
-        _ => InternKind::Constant,
+    let intern_kind = if cid.promoted.is_some() {
+        InternKind::Promoted
+    } else {
+        match tcx.static_mutability(cid.instance.def_id()) {
+            Some(m) => InternKind::Static(m),
+            None => InternKind::Constant,
+        }
     };
     intern_const_alloc_recursive(
         ecx,