properly fill a promoted's required_consts

then we can also make all_required_consts_are_checked a constant instead of a function

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -1179,9 +1179,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     ) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
         M::eval_mir_constant(self, *val, span, layout, |ecx, val, span, layout| {
             let const_val = val.eval(*ecx.tcx, ecx.param_env, span).map_err(|err| {
-                if M::all_required_consts_are_checked(self)
-                    && !matches!(err, ErrorHandled::TooGeneric(..))
-                {
+                if M::ALL_CONSTS_ARE_PRECHECKED && !matches!(err, ErrorHandled::TooGeneric(..)) {
                     // Looks like the const is not captued by `required_consts`, that's bad.
                     bug!("interpret const eval failure of {val:?} which is not in required_consts");
                 }

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -142,7 +142,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
 
     /// Determines whether `eval_mir_constant` can never fail because all required consts have
     /// already been checked before.
-    fn all_required_consts_are_checked(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
+    const ALL_CONSTS_ARE_PRECHECKED: bool = true;
 
     /// Whether memory accesses should be alignment-checked.
     fn enforce_alignment(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;