remove it

compiler/rustc_borrowck/src/invalidation.rs

@@ -289,11 +289,6 @@ impl<'cx, 'tcx> InvalidationGenerator<'cx, 'tcx> {
             | Rvalue::ShallowInitBox(ref operand, _ /*ty*/) => {
                 self.consume_operand(location, operand)
             }
-            Rvalue::CopyForDeref(ref place) => {
-                let op = &Operand::Copy(*place);
-                self.consume_operand(location, op);
-            }
-
             Rvalue::Len(place) | Rvalue::Discriminant(place) => {
                 let af = match *rvalue {
                     Rvalue::Len(..) => Some(ArtificialField::ArrayLength),

compiler/rustc_borrowck/src/lib.rs

@@ -1236,24 +1236,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             | Rvalue::ShallowInitBox(ref operand, _ /*ty*/) => {
                 self.consume_operand(location, (operand, span), flow_state)
             }
-            Rvalue::CopyForDeref(place) => {
-                self.access_place(
-                    location,
-                    (place, span),
-                    (Deep, Read(ReadKind::Copy)),
-                    LocalMutationIsAllowed::No,
-                    flow_state,
-                );
-
-                // Finally, check if path was already moved.
-                self.check_if_path_or_subpath_is_moved(
-                    location,
-                    InitializationRequiringAction::Use,
-                    (place.as_ref(), span),
-                    flow_state,
-                );
-            }
-
             Rvalue::Len(place) | Rvalue::Discriminant(place) => {
                 let af = match *rvalue {
                     Rvalue::Len(..) => Some(ArtificialField::ArrayLength),

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -2283,10 +2283,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             Rvalue::Use(operand) | Rvalue::UnaryOp(_, operand) => {
                 self.check_operand(operand, location);
             }
-            Rvalue::CopyForDeref(place) => {
-                let op = &Operand::Copy(*place);
-                self.check_operand(op, location);
-            }
 
             Rvalue::BinaryOp(_, box (left, right))
             | Rvalue::CheckedBinaryOp(_, box (left, right)) => {
@@ -2317,7 +2313,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             | Rvalue::BinaryOp(..)
             | Rvalue::CheckedBinaryOp(..)
             | Rvalue::NullaryOp(..)
-            | Rvalue::CopyForDeref(..)
             | Rvalue::UnaryOp(..)
             | Rvalue::Discriminant(..) => None,
 

compiler/rustc_codegen_cranelift/src/base.rs

@@ -503,11 +503,6 @@ fn codegen_stmt<'tcx>(
                     let val = codegen_operand(fx, operand);
                     lval.write_cvalue(fx, val);
                 }
-                Rvalue::CopyForDeref(place) => {
-                    let cplace = codegen_place(fx, place);
-                    let val = cplace.to_cvalue(fx);
-                    lval.write_cvalue(fx, val)
-                }
                 Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
                     let place = codegen_place(fx, place);
                     let ref_ = place.place_ref(fx, lval.layout());

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -8,7 +8,6 @@ use crate::traits::*;
 use crate::MemFlags;
 
 use rustc_middle::mir;
-use rustc_middle::mir::Operand;
 use rustc_middle::ty::cast::{CastTy, IntTy};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
 use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
@@ -345,10 +344,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 self.codegen_place_to_pointer(bx, place, mk_ref)
             }
 
-            mir::Rvalue::CopyForDeref(place) => {
-                let operand = self.codegen_operand(&mut bx, &Operand::Copy(place));
-                (bx, operand)
-            }
             mir::Rvalue::AddressOf(mutability, place) => {
                 let mk_ptr = move |tcx: TyCtxt<'tcx>, ty: Ty<'tcx>| {
                     tcx.mk_ptr(ty::TypeAndMut { ty, mutbl: mutability })
@@ -703,7 +698,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>, span: Span) -> bool {
         match *rvalue {
             mir::Rvalue::Ref(..) |
-            mir::Rvalue::CopyForDeref(..) |
             mir::Rvalue::AddressOf(..) |
             mir::Rvalue::Len(..) |
             mir::Rvalue::Cast(..) | // (*)

compiler/rustc_const_eval/src/interpret/step.rs

@@ -172,11 +172,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.copy_op(&op, &dest, /*allow_transmute*/ false)?;
             }
 
-            CopyForDeref(ref place) => {
-                let op = self.eval_place_to_op(*place, Some(dest.layout))?;
-                self.copy_op(&op, &dest, /* allow_transmute*/ false)?;
-            }
-
             BinaryOp(bin_op, box (ref left, ref right)) => {
                 let layout = binop_left_homogeneous(bin_op).then_some(dest.layout);
                 let left = self.read_immediate(&self.eval_operand(left, layout)?)?;

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -446,7 +446,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             Rvalue::ThreadLocalRef(_) => self.check_op(ops::ThreadLocalAccess),
 
             Rvalue::Use(_)
-            | Rvalue::CopyForDeref(..)
             | Rvalue::Repeat(..)
             | Rvalue::Discriminant(..)
             | Rvalue::Len(_)

compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -260,8 +260,6 @@ where
             in_place::<Q, _>(cx, in_local, place.as_ref())
         }
 
-        Rvalue::CopyForDeref(place) => in_place::<Q, _>(cx, in_local, place.as_ref()),
-
         Rvalue::Use(operand)
         | Rvalue::Repeat(operand, _)
         | Rvalue::UnaryOp(_, operand)

compiler/rustc_const_eval/src/transform/check_consts/resolver.rs

@@ -199,7 +199,6 @@ where
             mir::Rvalue::Cast(..)
             | mir::Rvalue::ShallowInitBox(..)
             | mir::Rvalue::Use(..)
-            | mir::Rvalue::CopyForDeref(..)
             | mir::Rvalue::ThreadLocalRef(..)
             | mir::Rvalue::Repeat(..)
             | mir::Rvalue::Len(..)

compiler/rustc_const_eval/src/transform/promote_consts.rs

@@ -494,11 +494,6 @@ impl<'tcx> Validator<'_, 'tcx> {
             Rvalue::Use(operand) | Rvalue::Repeat(operand, _) => {
                 self.validate_operand(operand)?;
             }
-            Rvalue::CopyForDeref(place) => {
-                let op = &Operand::Copy(*place);
-                self.validate_operand(op)?
-            }
-
             Rvalue::Discriminant(place) | Rvalue::Len(place) => {
                 self.validate_place(place.as_ref())?
             }

compiler/rustc_const_eval/src/transform/validate.rs

@@ -227,11 +227,24 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
         {
             // `Operand::Copy` is only supposed to be used with `Copy` types.
             if let Operand::Copy(place) = operand {
-                let ty = place.ty(&self.body.local_decls, self.tcx).ty;
-                let span = self.body.source_info(location).span;
+                // We skip `DerefTemp` values
+                let mut check = true;
+                if let Some(stmt) = self.body.stmt_at(location).left() {
+                    if let StatementKind::Assign(box (dest, Rvalue::Use(Operand::Copy(_)))) =
+                        stmt.kind
+                    {
+                        if self.body.local_decls[dest.local].is_deref_temp() {
+                            check = false;
+                        }
+                    }
+                }
+                if check {
+                    let ty = place.ty(&self.body.local_decls, self.tcx).ty;
+                    let span = self.body.source_info(location).span;
 
-                if !ty.is_copy_modulo_regions(self.tcx.at(span), self.param_env) {
-                    self.fail(location, format!("`Operand::Copy` with non-`Copy` type {}", ty));
+                    if !ty.is_copy_modulo_regions(self.tcx.at(span), self.param_env) {
+                        self.fail(location, format!("`Operand::Copy` with non-`Copy` type {}", ty));
+                    }
                 }
             }
         }
@@ -382,7 +395,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             };
         }
         match rvalue {
-            Rvalue::Use(_) | Rvalue::CopyForDeref(_) => {}
+            Rvalue::Use(_) => {}
             Rvalue::Aggregate(agg_kind, _) => {
                 let disallowed = match **agg_kind {
                     AggregateKind::Array(..) => false,
@@ -592,17 +605,9 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         ),
                     );
                 }
-                if let Rvalue::CopyForDeref(place) = rvalue {
-                    if !place.ty(&self.body.local_decls, self.tcx).ty.builtin_deref(true).is_some()
-                    {
-                        self.fail(
-                            location,
-                            "`CopyForDeref` should only be used for dereferenceable types",
-                        )
-                    }
-                }
                 // FIXME(JakobDegen): Check this for all rvalues, not just this one.
                 if let Rvalue::Use(Operand::Copy(src) | Operand::Move(src)) = rvalue {
+                    if !src.ty(&self.body.local_decls, self.tcx).ty.builtin_deref(true).is_some() {}
                     // The sides of an assignment must not alias. Currently this just checks whether
                     // the places are identical.
                     if dest == src {

compiler/rustc_middle/src/mir/mod.rs

@@ -1810,7 +1810,6 @@ impl<'tcx> Rvalue<'tcx> {
             Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => false,
 
             Rvalue::Use(_)
-            | Rvalue::CopyForDeref(_)
             | Rvalue::Repeat(_, _)
             | Rvalue::Ref(_, _, _)
             | Rvalue::ThreadLocalRef(_)
@@ -1905,8 +1904,6 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                 write!(fmt, "&{}{}{:?}", region, kind_str, place)
             }
 
-            CopyForDeref(ref place) => write!(fmt, "deref_copy {:#?}", place),
-
             AddressOf(mutability, ref place) => {
                 let kind_str = match mutability {
                     Mutability::Mut => "mut",

compiler/rustc_middle/src/mir/syntax.rs

@@ -1058,16 +1058,6 @@ pub enum Rvalue<'tcx> {
     /// initialized but its content as uninitialized. Like other pointer casts, this in general
     /// affects alias analysis.
     ShallowInitBox(Operand<'tcx>, Ty<'tcx>),
-
-    /// A CopyForDeref is equivalent to a read from a place at the
-    /// codegen level, but is treated specially by drop elaboration. When such a read happens, it
-    /// is guaranteed (via nature of the mir_opt `Derefer` in rustc_mir_transform/src/deref_separator)
-    /// that the only use of the returned value is a deref operation, immediately
-    /// followed by one or more projections. Drop elaboration treats this rvalue as if the
-    /// read never happened and just projects further. This allows simplifying various MIR
-    /// optimizations and codegen backends that previously had to handle deref operations anywhere
-    /// in a place.
-    CopyForDeref(Place<'tcx>),
 }
 
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]

compiler/rustc_middle/src/mir/tcx.rs

@@ -213,7 +213,6 @@ impl<'tcx> Rvalue<'tcx> {
                 }
             },
             Rvalue::ShallowInitBox(_, ty) => tcx.mk_box(ty),
-            Rvalue::CopyForDeref(ref place) => place.ty(local_decls, tcx).ty,
         }
     }
 

compiler/rustc_middle/src/mir/type_foldable.rs

@@ -122,7 +122,6 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
             Ref(region, bk, place) => {
                 Ref(region.try_fold_with(folder)?, bk, place.try_fold_with(folder)?)
             }
-            CopyForDeref(place) => CopyForDeref(place.try_fold_with(folder)?),
             AddressOf(mutability, place) => AddressOf(mutability, place.try_fold_with(folder)?),
             Len(place) => Len(place.try_fold_with(folder)?),
             Cast(kind, op, ty) => Cast(kind, op.try_fold_with(folder)?, ty.try_fold_with(folder)?),

compiler/rustc_middle/src/mir/type_visitable.rs

@@ -78,10 +78,6 @@ impl<'tcx> TypeVisitable<'tcx> for Rvalue<'tcx> {
         use crate::mir::Rvalue::*;
         match *self {
             Use(ref op) => op.visit_with(visitor),
-            CopyForDeref(ref place) => {
-                let op = &Operand::Copy(*place);
-                op.visit_with(visitor)
-            }
             Repeat(ref op, _) => op.visit_with(visitor),
             ThreadLocalRef(did) => did.visit_with(visitor),
             Ref(region, _, ref place) => {

compiler/rustc_middle/src/mir/visit.rs

@@ -711,14 +711,6 @@ macro_rules! make_mir_visitor {
                         };
                         self.visit_place(path, ctx, location);
                     }
-                    Rvalue::CopyForDeref(place) => {
-                        self.visit_place(
-                            place,
-                            PlaceContext::NonMutatingUse(NonMutatingUseContext::Inspect),
-                            location
-                        );
-                    }
-
                     Rvalue::AddressOf(m, path) => {
                         let ctx = match m {
                             Mutability::Mut => PlaceContext::MutatingUse(

compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs

@@ -102,8 +102,7 @@ where
             | mir::Rvalue::NullaryOp(..)
             | mir::Rvalue::UnaryOp(..)
             | mir::Rvalue::Discriminant(..)
-            | mir::Rvalue::Aggregate(..)
-            | mir::Rvalue::CopyForDeref(..) => {}
+            | mir::Rvalue::Aggregate(..) => {}
         }
     }
 

compiler/rustc_mir_dataflow/src/move_paths/builder.rs

@@ -284,31 +284,30 @@ struct Gatherer<'b, 'a, 'tcx> {
 impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
     fn gather_statement(&mut self, stmt: &Statement<'tcx>) {
         match &stmt.kind {
-            StatementKind::Assign(box (place, Rvalue::CopyForDeref(reffed))) => {
-                assert!(place.projection.is_empty());
-                if self.builder.body.local_decls[place.local].is_deref_temp() {
-                    self.builder.un_derefer.derefer_sidetable.insert(place.local, *reffed);
-                }
-            }
             StatementKind::Assign(box (place, rval)) => {
-                self.create_move_path(*place);
-                if let RvalueInitializationState::Shallow = rval.initialization_state() {
-                    // Box starts out uninitialized - need to create a separate
-                    // move-path for the interior so it will be separate from
-                    // the exterior.
-                    self.create_move_path(self.builder.tcx.mk_place_deref(*place));
-                    self.gather_init(place.as_ref(), InitKind::Shallow);
+                if self.builder.body.local_decls[place.local].is_deref_temp() {
+                    if let Rvalue::Use(Operand::Copy(reffed)) = rval {
+                        self.builder.un_derefer.derefer_sidetable.insert(place.local, *reffed);
+                    }
                 } else {
-                    self.gather_init(place.as_ref(), InitKind::Deep);
+                    self.create_move_path(*place);
+                    if let RvalueInitializationState::Shallow = rval.initialization_state() {
+                        // Box starts out uninitialized - need to create a separate
+                        // move-path for the interior so it will be separate from
+                        // the exterior.
+                        self.create_move_path(self.builder.tcx.mk_place_deref(*place));
+                        self.gather_init(place.as_ref(), InitKind::Shallow);
+                    } else {
+                        self.gather_init(place.as_ref(), InitKind::Deep);
+                    }
+                    self.gather_rvalue(rval);
                 }
-                self.gather_rvalue(rval);
             }
             StatementKind::FakeRead(box (_, place)) => {
                 self.create_move_path(*place);
             }
             StatementKind::StorageLive(_) => {}
             StatementKind::StorageDead(local) => {
-                // DerefTemp locals (results of CopyForDeref) don't actually move anything.
                 if !self.builder.un_derefer.derefer_sidetable.contains_key(&local) {
                     self.gather_move(Place::from(*local));
                 }
@@ -345,7 +344,6 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
                     self.gather_operand(operand);
                 }
             }
-            Rvalue::CopyForDeref(..) => unreachable!(),
             Rvalue::Ref(..)
             | Rvalue::AddressOf(..)
             | Rvalue::Discriminant(..)

compiler/rustc_mir_dataflow/src/un_derefer.rs

@@ -23,7 +23,7 @@ impl<'tcx> UnDerefer<'tcx> {
         for (_bb, data) in body.basic_blocks().iter_enumerated() {
             for stmt in data.statements.iter() {
                 match stmt.kind {
-                    StatementKind::Assign(box (place, Rvalue::CopyForDeref(reffed))) => {
+                    StatementKind::Assign(box (place, Rvalue::Use(Operand::Copy(reffed)))) => {
                         if body.local_decls[place.local].is_deref_temp() {
                             self.derefer_sidetable.insert(place.local, reffed);
                         }

compiler/rustc_mir_transform/src/const_prop.rs

@@ -621,7 +621,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             // There's no other checking to do at this time.
             Rvalue::Aggregate(..)
             | Rvalue::Use(..)
-            | Rvalue::CopyForDeref(..)
             | Rvalue::Repeat(..)
             | Rvalue::Len(..)
             | Rvalue::Cast(..)

compiler/rustc_mir_transform/src/const_prop_lint.rs

@@ -693,7 +693,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             // There's no other checking to do at this time.
             Rvalue::Aggregate(..)
             | Rvalue::Use(..)
-            | Rvalue::CopyForDeref(..)
             | Rvalue::Repeat(..)
             | Rvalue::Len(..)
             | Rvalue::Cast(..)

compiler/rustc_mir_transform/src/deref_separator.rs

@@ -55,7 +55,7 @@ impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> {
                     self.patcher.add_assign(
                         loc,
                         Place::from(temp),
-                        Rvalue::CopyForDeref(deref_place),
+                        Rvalue::Use(Operand::Copy(deref_place)),
                     );
                     place_local = temp;
                     last_len = p_ref.projection.len();

compiler/rustc_mir_transform/src/separate_const_switch.rs

@@ -218,7 +218,6 @@ fn is_likely_const<'tcx>(mut tracked_place: Place<'tcx>, block: &BasicBlockData<
                         // These rvalues move the place to track
                         Rvalue::Cast(_, Operand::Copy(place) | Operand::Move(place), _)
                         | Rvalue::Use(Operand::Copy(place) | Operand::Move(place))
-                        | Rvalue::CopyForDeref(place)
                         | Rvalue::UnaryOp(_, Operand::Copy(place) | Operand::Move(place))
                         | Rvalue::Discriminant(place) => tracked_place = place,
                     }
@@ -280,7 +279,6 @@ fn find_determining_place<'tcx>(
                     // that may be const in the predecessor
                     Rvalue::Use(Operand::Move(new) | Operand::Copy(new))
                     | Rvalue::UnaryOp(_, Operand::Copy(new) | Operand::Move(new))
-                    | Rvalue::CopyForDeref(new)
                     | Rvalue::Cast(_, Operand::Move(new) | Operand::Copy(new), _)
                     | Rvalue::Repeat(Operand::Move(new) | Operand::Copy(new), _)
                     | Rvalue::Discriminant(new)