Rollup merge of #129969 - GrigorenkoPV:boxed-ty, r=compiler-errors

Make `Ty::boxed_ty` return an `Option`

Looks like a good place to use Rust's type system.

---

Most of https://github.com/rust-lang/rust/blob/4ac7bcbaad8d6fd7a51bdf1b696cbc3ba4c796cf/compiler/rustc_middle/src/ty/sty.rs#L971-L1963 looks like it could be moved to `TyKind` (then I guess  `Ty` should be made to deref to `TyKind`).

1 files changed, 8 insertions, 4 deletions

diff --git a/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs b/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
index 5dd82f40163..66e49d556e2 100644
--- a/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
@@ -62,11 +62,13 @@ impl<'tcx, 'a> MutVisitor<'tcx> for ElaborateBoxDerefVisitor<'tcx, 'a> {
         let base_ty = self.local_decls[place.local].ty;
 
         // Derefer ensures that derefs are always the first projection
-        if place.projection.first() == Some(&PlaceElem::Deref) && base_ty.is_box() {
+        if let Some(PlaceElem::Deref) = place.projection.first()
+            && let Some(boxed_ty) = base_ty.boxed_ty()
+        {
             let source_info = self.local_decls[place.local].source_info;
 
             let (unique_ty, nonnull_ty, ptr_ty) =
-                build_ptr_tys(tcx, base_ty.boxed_ty(), self.unique_did, self.nonnull_did);
+                build_ptr_tys(tcx, boxed_ty, self.unique_did, self.nonnull_did);
 
             let ptr_local = self.patch.new_temp(ptr_ty, source_info.span);
 
@@ -120,13 +122,15 @@ impl<'tcx> crate::MirPass<'tcx> for ElaborateBoxDerefs {
                     for (base, elem) in place.iter_projections() {
                         let base_ty = base.ty(&body.local_decls, tcx).ty;
 
-                        if elem == PlaceElem::Deref && base_ty.is_box() {
+                        if let PlaceElem::Deref = elem
+                            && let Some(boxed_ty) = base_ty.boxed_ty()
+                        {
                             // Clone the projections before us, since now we need to mutate them.
                             let new_projections =
                                 new_projections.get_or_insert_with(|| base.projection.to_vec());
 
                             let (unique_ty, nonnull_ty, ptr_ty) =
-                                build_ptr_tys(tcx, base_ty.boxed_ty(), unique_did, nonnull_did);
+                                build_ptr_tys(tcx, boxed_ty, unique_did, nonnull_did);
 
                             new_projections.extend_from_slice(&build_projection(
                                 unique_ty, nonnull_ty, ptr_ty,