Rollup merge of #109435 - oli-obk:🇨🇭🥚_copy_op, r=RalfJung

Detect uninhabited types early in const eval

r? `@RalfJung`

implements https://github.com/rust-lang/rust/pull/108442#discussion_r1143003840

this is a breaking change, as some UB during const eval is now detected instead of silently being ignored. Users can see this and other UB that may cause future breakage with `-Zextra-const-ub-checks` or just by running miri on their code, which sets that flag by default.

compiler/rustc_mir_transform/src/const_prop.rs

@@ -180,7 +180,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx>
     }
 
     #[inline(always)]
-    fn enforce_validity(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
+    fn enforce_validity(_ecx: &InterpCx<'mir, 'tcx, Self>, _layout: TyAndLayout<'tcx>) -> bool {
         false // for now, we don't enforce validity
     }
     fn alignment_check_failed(

compiler/rustc_mir_transform/src/dataflow_const_prop.rs

@@ -8,6 +8,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def::DefKind;
 use rustc_middle::mir::visit::{MutVisitor, Visitor};
 use rustc_middle::mir::*;
+use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_mir_dataflow::value_analysis::{Map, State, TrackElem, ValueAnalysis, ValueOrPlace};
 use rustc_mir_dataflow::{lattice::FlatSet, Analysis, ResultsVisitor, SwitchIntEdgeEffects};
@@ -548,7 +549,7 @@ impl<'mir, 'tcx> rustc_const_eval::interpret::Machine<'mir, 'tcx> for DummyMachi
         unimplemented!()
     }
 
-    fn enforce_validity(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
+    fn enforce_validity(_ecx: &InterpCx<'mir, 'tcx, Self>, _layout: TyAndLayout<'tcx>) -> bool {
         unimplemented!()
     }
     fn alignment_check_failed(