refactor: remove Adjust::ReborrowPin

Author: frank-king

compiler/rustc_hir_typeck/src/coercion.rs

@@ -853,7 +853,13 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
 
         // To complete the reborrow, we need to make sure we can unify the inner types, and if so we
         // add the adjustments.
-        self.unify_and(a, b, [], Adjust::ReborrowPin(mut_b), ForceLeakCheck::No)
+        self.unify_and(
+            a,
+            b,
+            [Adjustment { kind: Adjust::Deref(DerefAdjustKind::Pin), target: a_ty }],
+            Adjust::Borrow(AutoBorrow::Pin(mut_b)),
+            ForceLeakCheck::No,
+        )
     }
 
     /// Coerce pinned reference to regular reference or vice versa

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -749,16 +749,6 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                 adjustment::Adjust::Borrow(ref autoref) => {
                     self.walk_autoref(expr, &place_with_id, autoref);
                 }
-
-                adjustment::Adjust::ReborrowPin(mutbl) => {
-                    // Reborrowing a Pin is like a combinations of a deref and a borrow, so we do
-                    // both.
-                    let bk = match mutbl {
-                        ty::Mutability::Not => ty::BorrowKind::Immutable,
-                        ty::Mutability::Mut => ty::BorrowKind::Mutable,
-                    };
-                    self.delegate.borrow_mut().borrow(&place_with_id, place_with_id.hir_id, bk);
-                }
             }
             place_with_id = self.cat_expr_adjusted(expr, place_with_id, adjustment)?;
         }
@@ -1301,8 +1291,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
 
             adjustment::Adjust::NeverToAny
             | adjustment::Adjust::Pointer(_)
-            | adjustment::Adjust::Borrow(_)
-            | adjustment::Adjust::ReborrowPin(..) => {
+            | adjustment::Adjust::Borrow(_) => {
                 // Result is an rvalue.
                 Ok(self.cat_rvalue(expr.hir_id, target))
             }

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -285,10 +285,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 Adjust::Pointer(_pointer_coercion) => {
                     // FIXME(const_trait_impl): We should probably enforce these.
                 }
-                Adjust::ReborrowPin(_mutability) => {
-                    // FIXME(const_trait_impl): We could enforce these; they correspond to
-                    // `&mut T: DerefMut` tho, so it's kinda moot.
-                }
                 Adjust::Borrow(_) => {
                     // No effects to enforce here.
                 }

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -18,7 +18,8 @@ use rustc_lint::builtin::{
 };
 use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::adjustment::{
-    Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCoercion,
+    Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, DerefAdjustKind,
+    PointerCoercion,
 };
 use rustc_middle::ty::{
     self, AssocContainer, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TyCtxt,
@@ -243,12 +244,16 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                             ty::Ref(_, ty, _) => *ty,
                             _ => bug!("Expected a reference type for argument to Pin"),
                         };
+                        adjustments.push(Adjustment {
+                            kind: Adjust::Deref(DerefAdjustKind::Pin),
+                            target: inner_ty,
+                        });
                         Ty::new_pinned_ref(self.tcx, region, inner_ty, mutbl)
                     }
                     _ => bug!("Cannot adjust receiver type for reborrowing pin of {target:?}"),
                 };
-
-                adjustments.push(Adjustment { kind: Adjust::ReborrowPin(mutbl), target });
+                adjustments
+                    .push(Adjustment { kind: Adjust::Borrow(AutoBorrow::Pin(mutbl)), target });
             }
             None => {}
         }

compiler/rustc_lint/src/autorefs.rs

@@ -173,7 +173,6 @@ fn has_implicit_borrow(Adjustment { kind, .. }: &Adjustment<'_>) -> Option<(Muta
         &Adjust::Borrow(AutoBorrow::Ref(mutbl)) => Some((mutbl.into(), false)),
         Adjust::NeverToAny
         | Adjust::Pointer(..)
-        | Adjust::ReborrowPin(..)
         | Adjust::Deref(DerefAdjustKind::Builtin | DerefAdjustKind::Pin)
         | Adjust::Borrow(AutoBorrow::RawPtr(..) | AutoBorrow::Pin(..)) => None,
     }

compiler/rustc_middle/src/ty/adjustment.rs

@@ -103,10 +103,6 @@ pub enum Adjust {
     Borrow(AutoBorrow),
 
     Pointer(PointerCoercion),
-
-    /// Take a pinned reference and reborrow as a `Pin<&mut T>` or `Pin<&T>`.
-    // FIXME(pin_ergonomics): This can be replaced with a `Deref(Pin)` followed by a `Borrow(Pin)`
-    ReborrowPin(hir::Mutability),
 }
 
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -219,68 +219,6 @@ impl<'tcx> ThirBuildCx<'tcx> {
                     base: AdtExprBase::None,
                 }));
 
-                debug!(?kind);
-                kind
-            }
-            Adjust::ReborrowPin(mutbl) => {
-                debug!("apply ReborrowPin adjustment");
-                // Rewrite `$expr` as `Pin { __pointer: &(mut)? *($expr).__pointer }`
-
-                // We'll need these types later on
-                let pin_ty_args = match expr.ty.kind() {
-                    ty::Adt(_, args) => args,
-                    _ => bug!("ReborrowPin with non-Pin type"),
-                };
-                let pin_ty = pin_ty_args.iter().next().unwrap().expect_ty();
-                let ptr_target_ty = match pin_ty.kind() {
-                    ty::Ref(_, ty, _) => *ty,
-                    _ => bug!("ReborrowPin with non-Ref type"),
-                };
-
-                // pointer = ($expr).__pointer
-                let pointer_target = ExprKind::Field {
-                    lhs: self.thir.exprs.push(expr),
-                    variant_index: FIRST_VARIANT,
-                    name: FieldIdx::ZERO,
-                };
-                let arg = Expr { temp_scope_id, ty: pin_ty, span, kind: pointer_target };
-                let arg = self.thir.exprs.push(arg);
-
-                // arg = *pointer
-                let expr = ExprKind::Deref { arg };
-                let arg = self.thir.exprs.push(Expr {
-                    temp_scope_id,
-                    ty: ptr_target_ty,
-                    span,
-                    kind: expr,
-                });
-
-                // expr = &mut target
-                let borrow_kind = match mutbl {
-                    hir::Mutability::Mut => BorrowKind::Mut { kind: mir::MutBorrowKind::Default },
-                    hir::Mutability::Not => BorrowKind::Shared,
-                };
-                let new_pin_target =
-                    Ty::new_ref(self.tcx, self.tcx.lifetimes.re_erased, ptr_target_ty, mutbl);
-                let expr = self.thir.exprs.push(Expr {
-                    temp_scope_id,
-                    ty: new_pin_target,
-                    span,
-                    kind: ExprKind::Borrow { borrow_kind, arg },
-                });
-
-                // kind = Pin { __pointer: pointer }
-                let pin_did = self.tcx.require_lang_item(rustc_hir::LangItem::Pin, span);
-                let args = self.tcx.mk_args(&[new_pin_target.into()]);
-                let kind = ExprKind::Adt(Box::new(AdtExpr {
-                    adt_def: self.tcx.adt_def(pin_did),
-                    variant_index: FIRST_VARIANT,
-                    args,
-                    fields: Box::new([FieldExpr { name: FieldIdx::ZERO, expr }]),
-                    user_ty: None,
-                    base: AdtExprBase::None,
-                }));
-
                 debug!(?kind);
                 kind
             }