handle safety lubbing correctly

Author: BoxyUwU

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1062,7 +1062,10 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
 
             Rvalue::Cast(cast_kind, op, ty) => {
                 match *cast_kind {
-                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, coercion_source) => {
+                    CastKind::PointerCoercion(
+                        PointerCoercion::ReifyFnPointer(target_safety),
+                        coercion_source,
+                    ) => {
                         let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
                         let src_ty = op.ty(self.body, tcx);
                         let mut src_sig = src_ty.fn_sig(tcx);
@@ -1079,6 +1082,10 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             src_sig = safe_sig;
                         }
 
+                        if src_sig.safety().is_safe() && target_safety.is_unsafe() {
+                            src_sig = tcx.safe_to_unsafe_sig(src_sig);
+                        }
+
                         // HACK: This shouldn't be necessary... We can remove this when we actually
                         // get binders with where clauses, then elaborate implied bounds into that
                         // binder, and implement a higher-ranked subtyping algorithm that actually

compiler/rustc_codegen_cranelift/src/base.rs

@@ -665,7 +665,7 @@ fn codegen_stmt<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, cur_block: Block, stmt:
                     lval.write_cvalue(fx, res);
                 }
                 Rvalue::Cast(
-                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _),
+                    CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer(_), _),
                     ref operand,
                     to_ty,
                 ) => {

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -399,7 +399,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         let lladdr = bx.ptrtoint(llptr, llcast_ty);
                         OperandValue::Immediate(lladdr)
                     }
-                    mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer(_), _) => {
                         match *operand.layout.ty.kind() {
                             ty::FnDef(def_id, args) => {
                                 let instance = ty::Instance::resolve_for_fn_ptr(

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -627,7 +627,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     | PointerCoercion::ArrayToPointer
                     | PointerCoercion::UnsafeFnPointer
                     | PointerCoercion::ClosureFnPointer(_)
-                    | PointerCoercion::ReifyFnPointer,
+                    | PointerCoercion::ReifyFnPointer(_),
                     _,
                 ),
                 _,

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -74,7 +74,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 bug!("{cast_kind:?} casts are for borrowck only, not runtime MIR");
             }
 
-            CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, _) => {
+            CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer(_), _) => {
                 // All reifications must be monomorphic, bail out otherwise.
                 ensure_monomorphic_enough(*self.tcx, src.layout.ty)?;