+
+#[track_caller]
+pub(crate) fn assert_assignable<'tcx>(
+ fx: &FunctionCx<'_, 'tcx, impl Module>,
+ from_ty: Ty<'tcx>,
+ to_ty: Ty<'tcx>,
+) {
+ match (from_ty.kind(), to_ty.kind()) {
+ (ty::Ref(_, a, _), ty::Ref(_, b, _))
+ | (
+ ty::RawPtr(TypeAndMut { ty: a, mutbl: _ }),
+ ty::RawPtr(TypeAndMut { ty: b, mutbl: _ }),
+ ) => {
+ assert_assignable(fx, a, b);
+ }
+ (ty::Ref(_, a, _), ty::RawPtr(TypeAndMut { ty: b, mutbl: _ }))
+ | (ty::RawPtr(TypeAndMut { ty: a, mutbl: _ }), ty::Ref(_, b, _)) => {
+ assert_assignable(fx, a, b);
+ }
+ (ty::FnPtr(_), ty::FnPtr(_)) => {
+ let from_sig = fx.tcx.normalize_erasing_late_bound_regions(
+ ParamEnv::reveal_all(),
+ from_ty.fn_sig(fx.tcx),
+ );
+ let to_sig = fx
+ .tcx
+ .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), to_ty.fn_sig(fx.tcx));
+ assert_eq!(
+ from_sig, to_sig,
+ "Can't write fn ptr with incompatible sig {:?} to place with sig {:?}\n\n{:#?}",
+ from_sig, to_sig, fx,
+ );
+ // fn(&T) -> for<'l> fn(&'l T) is allowed
+ }
+ (&ty::Dynamic(from_traits, _), &ty::Dynamic(to_traits, _)) => {
+ for (from, to) in from_traits.iter().zip(to_traits) {
+ let from = fx
+ .tcx
+ .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), from);
+ let to = fx
+ .tcx
+ .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), to);
+ assert_eq!(
+ from, to,
+ "Can't write trait object of incompatible traits {:?} to place with traits {:?}\n\n{:#?}",
+ from_traits, to_traits, fx,
+ );
+ }
+ // dyn for<'r> Trait<'r> -> dyn Trait<'_> is allowed
+ }
+ _ => {
+ assert_eq!(
+ from_ty, to_ty,
+ "Can't write value with incompatible type {:?} to place with type {:?}\n\n{:#?}",
+ from_ty, to_ty, fx,
+ );
+ }
+ }
+}