interpret: sanity-check that required_consts captures all consts that can fail

compiler/rustc_const_eval/src/const_eval/dummy_machine.rs

@@ -46,6 +46,12 @@ impl<'mir, 'tcx: 'mir> interpret::Machine<'mir, 'tcx> for DummyMachine {
     type MemoryKind = !;
     const PANIC_ON_ALLOC_FAIL: bool = true;
 
+    #[inline(always)]
+    fn all_required_consts_are_checked(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
+        // We want to just eval random consts in the program, so `eval_mir_const` can fail.
+        false
+    }
+
     #[inline(always)]
     fn enforce_alignment(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
         false // no reason to enforce alignment

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -375,6 +375,20 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
 
     const PANIC_ON_ALLOC_FAIL: bool = false; // will be raised as a proper error
 
+    #[inline]
+    fn all_required_consts_are_checked(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
+        // Generally we expect required_consts to be properly filled, except for promoteds where
+        // storing these consts shows up negatively in benchmarks. A promoted can only be relevant
+        // if its parent MIR is relevant, and the consts in the promoted will be in the parent's
+        // `required_consts`, so we are still sure to catch any const-eval bugs, just a bit less
+        // directly.
+        if ecx.frame_idx() == 0 && ecx.frame().body.source.promoted.is_some() {
+            false
+        } else {
+            true
+        }
+    }
+
     #[inline(always)]
     fn enforce_alignment(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
         matches!(ecx.machine.check_alignment, CheckAlignment::Error)