Remove DropAndReplace terminator

PR 107844 made DropAndReplace unused, let's remove it completely
from the codebase.

compiler/rustc_borrowck/src/invalidation.rs

@@ -118,15 +118,6 @@ fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location
                     LocalMutationIsAllowed::Yes,
                 );
             }
-            TerminatorKind::DropAndReplace {
-                place: drop_place,
-                value: new_value,
-                target: _,
-                unwind: _,
-            } => {
-                self.mutate_place(location, *drop_place, Deep);
-                self.consume_operand(location, new_value);
-            }
             TerminatorKind::Call {
                 func,
                 args,

compiler/rustc_borrowck/src/lib.rs

@@ -744,15 +744,6 @@ fn visit_terminator_before_primary_effect(
                     flow_state,
                 );
             }
-            TerminatorKind::DropAndReplace {
-                place: drop_place,
-                value: new_value,
-                target: _,
-                unwind: _,
-            } => {
-                self.mutate_place(loc, (*drop_place, span), Deep, flow_state);
-                self.consume_operand(loc, (new_value, span), flow_state);
-            }
             TerminatorKind::Call {
                 func,
                 args,
@@ -867,7 +858,6 @@ fn visit_terminator_after_primary_effect(
             | TerminatorKind::Assert { .. }
             | TerminatorKind::Call { .. }
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::FalseEdge { real_target: _, imaginary_target: _ }
             | TerminatorKind::FalseUnwind { real_target: _, unwind: _ }
             | TerminatorKind::Goto { .. }

compiler/rustc_borrowck/src/type_check/liveness/trace.rs

@@ -435,8 +435,7 @@ fn compute_drop_live_points_for_block(&mut self, mpi: MovePathIndex, term_point:
         //
         // What we *actually* generate is a store to a temporary
         // for the call (`TMP = call()...`) and then a
-        // `DropAndReplace` to swap that with `X`
+        // `Drop(X)` followed by `X = TMP`  to swap that with `X`.
-        // (`DropAndReplace` has very particular semantics).
     }
 }
 

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1312,24 +1312,6 @@ fn check_terminator(
                 // no checks needed for these
             }
 
-            TerminatorKind::DropAndReplace { place, value, target: _, unwind: _ } => {
-                let place_ty = place.ty(body, tcx).ty;
-                let rv_ty = value.ty(body, tcx);
-
-                let locations = term_location.to_locations();
-                if let Err(terr) =
-                    self.sub_types(rv_ty, place_ty, locations, ConstraintCategory::Assignment)
-                {
-                    span_mirbug!(
-                        self,
-                        term,
-                        "bad DropAndReplace ({:?} = {:?}): {:?}",
-                        place_ty,
-                        rv_ty,
-                        terr
-                    );
-                }
-            }
             TerminatorKind::SwitchInt { discr, .. } => {
                 self.check_operand(discr, term_location);
 
@@ -1629,7 +1611,6 @@ fn check_iscleanup(&mut self, body: &Body<'tcx>, block_data: &BasicBlockData<'tc
             }
             TerminatorKind::Unreachable => {}
             TerminatorKind::Drop { target, unwind, .. }
-            | TerminatorKind::DropAndReplace { target, unwind, .. }
             | TerminatorKind::Assert { target, cleanup: unwind, .. } => {
                 self.assert_iscleanup(body, block_data, target, is_cleanup);
                 if let Some(unwind) = unwind {

compiler/rustc_borrowck/src/used_muts.rs

@@ -71,9 +71,6 @@ fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location
             TerminatorKind::Call { destination, .. } => {
                 self.remove_never_initialized_mut_locals(*destination);
             }
-            TerminatorKind::DropAndReplace { place, .. } => {
-                self.remove_never_initialized_mut_locals(*place);
-            }
             _ => {}
         }
 

compiler/rustc_codegen_cranelift/src/base.rs

@@ -499,7 +499,6 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
             TerminatorKind::Yield { .. }
             | TerminatorKind::FalseEdge { .. }
             | TerminatorKind::FalseUnwind { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::GeneratorDrop => {
                 bug!("shouldn't exist at codegen {:?}", bb_data.terminator());
             }

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -543,8 +543,7 @@ pub(crate) fn mir_operand_get_const_val<'tcx>(
                     | TerminatorKind::Unreachable
                     | TerminatorKind::Drop { .. }
                     | TerminatorKind::Assert { .. } => {}
-                    TerminatorKind::DropAndReplace { .. }
+                    TerminatorKind::Yield { .. }
-                    | TerminatorKind::Yield { .. }
                     | TerminatorKind::GeneratorDrop
                     | TerminatorKind::FalseEdge { .. }
                     | TerminatorKind::FalseUnwind { .. } => unreachable!(),

compiler/rustc_codegen_ssa/src/mir/analyze.rs

@@ -295,7 +295,6 @@ fn discover_masters<'tcx>(
                 TerminatorKind::Call { cleanup: unwind, .. }
                 | TerminatorKind::InlineAsm { cleanup: unwind, .. }
                 | TerminatorKind::Assert { cleanup: unwind, .. }
-                | TerminatorKind::DropAndReplace { unwind, .. }
                 | TerminatorKind::Drop { unwind, .. } => {
                     if let Some(unwind) = unwind {
                         debug!(

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -1305,10 +1305,6 @@ fn codegen_terminator(
                     mergeable_succ(),
                 ),
 
-            mir::TerminatorKind::DropAndReplace { .. } => {
-                bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
-            }
-
             mir::TerminatorKind::Call {
                 ref func,
                 ref args,

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -171,11 +171,7 @@ pub(super) fn eval_terminator(
             Unreachable => throw_ub!(Unreachable),
 
             // These should never occur for MIR we actually run.
-            DropAndReplace { .. }
+            FalseEdge { .. } | FalseUnwind { .. } | Yield { .. } | GeneratorDrop => span_bug!(
-            | FalseEdge { .. }
-            | FalseUnwind { .. }
-            | Yield { .. }
-            | GeneratorDrop => span_bug!(
                 terminator.source_info.span,
                 "{:#?} should have been eliminated by MIR pass",
                 terminator.kind

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

@@ -977,8 +977,7 @@ fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location
 
             // Forbid all `Drop` terminators unless the place being dropped is a local with no
             // projections that cannot be `NeedsNonConstDrop`.
-            TerminatorKind::Drop { place: dropped_place, .. }
+            TerminatorKind::Drop { place: dropped_place, .. } => {
-            | TerminatorKind::DropAndReplace { place: dropped_place, .. } => {
                 // If we are checking live drops after drop-elaboration, don't emit duplicate
                 // errors here.
                 if super::post_drop_elaboration::checking_enabled(self.ccx) {

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

@@ -80,8 +80,7 @@ fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Loc
         trace!("visit_terminator: terminator={:?} location={:?}", terminator, location);
 
         match &terminator.kind {
-            mir::TerminatorKind::Drop { place: dropped_place, .. }
+            mir::TerminatorKind::Drop { place: dropped_place, .. } => {
-            | mir::TerminatorKind::DropAndReplace { place: dropped_place, .. } => {
                 let dropped_ty = dropped_place.ty(self.body, self.tcx).ty;
                 if !NeedsNonConstDrop::in_any_value_of_ty(self.ccx, dropped_ty) {
                     // Instead of throwing a bug, we just return here. This is because we have to

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

@@ -222,18 +222,6 @@ fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Loc
         // The effect of assignment to the return place in `TerminatorKind::Call` is not applied
         // here; that occurs in `apply_call_return_effect`.
 
-        if let mir::TerminatorKind::DropAndReplace { value, place, .. } = &terminator.kind {
-            let qualif = qualifs::in_operand::<Q, _>(
-                self.ccx,
-                &mut |l| self.state.qualif.contains(l),
-                value,
-            );
-
-            if !place.is_indirect() {
-                self.assign_qualif_direct(place, qualif);
-            }
-        }
-
         // We ignore borrow on drop because custom drop impls are not allowed in consts.
         // FIXME: Reconsider if accounting for borrows in drops is necessary for const drop.
 

compiler/rustc_const_eval/src/transform/validate.rs

@@ -835,18 +835,6 @@ fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location
                     self.check_edge(location, *unwind, EdgeKind::Unwind);
                 }
             }
-            TerminatorKind::DropAndReplace { target, unwind, .. } => {
-                if self.mir_phase >= MirPhase::Runtime(RuntimePhase::Initial) {
-                    self.fail(
-                        location,
-                        "`DropAndReplace` should have been removed during drop elaboration",
-                    );
-                }
-                self.check_edge(location, *target, EdgeKind::Normal);
-                if let Some(unwind) = unwind {
-                    self.check_edge(location, *unwind, EdgeKind::Unwind);
-                }
-            }
             TerminatorKind::Call { func, args, destination, target, cleanup, .. } => {
                 let func_ty = func.ty(&self.body.local_decls, self.tcx);
                 match func_ty.kind() {

compiler/rustc_middle/src/mir/spanview.rs

@@ -265,7 +265,6 @@ pub fn terminator_kind_name(term: &Terminator<'_>) -> &'static str {
         Return => "Return",
         Unreachable => "Unreachable",
         Drop { .. } => "Drop",
-        DropAndReplace { .. } => "DropAndReplace",
         Call { .. } => "Call",
         Assert { .. } => "Assert",
         Yield { .. } => "Yield",

compiler/rustc_middle/src/mir/syntax.rs

@@ -133,7 +133,6 @@ pub enum AnalysisPhase {
 pub enum RuntimePhase {
     /// In addition to the semantic changes, beginning with this phase, the following variants are
     /// disallowed:
-    /// * [`TerminatorKind::DropAndReplace`]
     /// * [`TerminatorKind::Yield`]
     /// * [`TerminatorKind::GeneratorDrop`]
     /// * [`Rvalue::Aggregate`] for any `AggregateKind` except `Array`
@@ -596,43 +595,6 @@ pub enum TerminatorKind<'tcx> {
     /// > consider indirect assignments.
     Drop { place: Place<'tcx>, target: BasicBlock, unwind: Option<BasicBlock> },
 
-    /// Drops the place and assigns a new value to it.
-    ///
-    /// This first performs the exact same operation as the pre drop-elaboration `Drop` terminator;
-    /// it then additionally assigns the `value` to the `place` as if by an assignment statement.
-    /// This assignment occurs both in the unwind and the regular code paths. The semantics are best
-    /// explained by the elaboration:
-    ///
-    /// ```ignore (MIR)
-    /// BB0 {
-    ///   DropAndReplace(P <- V, goto BB1, unwind BB2)
-    /// }
-    /// ```
-    ///
-    /// becomes
-    ///
-    /// ```ignore (MIR)
-    /// BB0 {
-    ///   Drop(P, goto BB1, unwind BB2)
-    /// }
-    /// BB1 {
-    ///   // P is now uninitialized
-    ///   P <- V
-    /// }
-    /// BB2 {
-    ///   // P is now uninitialized -- its dtor panicked
-    ///   P <- V
-    /// }
-    /// ```
-    ///
-    /// Disallowed after drop elaboration.
-    DropAndReplace {
-        place: Place<'tcx>,
-        value: Operand<'tcx>,
-        target: BasicBlock,
-        unwind: Option<BasicBlock>,
-    },
-
     /// Roughly speaking, evaluates the `func` operand and the arguments, and starts execution of
     /// the referred to function. The operand types must match the argument types of the function.
     /// The return place type must match the return type. The type of the `func` operand must be

compiler/rustc_middle/src/mir/terminator.rs

@@ -148,7 +148,6 @@ pub fn successors(&self) -> Successors<'_> {
             | Call { target: None, cleanup: Some(t), .. }
             | Call { target: Some(t), cleanup: None, .. }
             | Yield { resume: t, drop: None, .. }
-            | DropAndReplace { target: t, unwind: None, .. }
             | Drop { target: t, unwind: None, .. }
             | Assert { target: t, cleanup: None, .. }
             | FalseUnwind { real_target: t, unwind: None }
@@ -158,7 +157,6 @@ pub fn successors(&self) -> Successors<'_> {
             }
             Call { target: Some(t), cleanup: Some(ref u), .. }
             | Yield { resume: t, drop: Some(ref u), .. }
-            | DropAndReplace { target: t, unwind: Some(ref u), .. }
             | Drop { target: t, unwind: Some(ref u), .. }
             | Assert { target: t, cleanup: Some(ref u), .. }
             | FalseUnwind { real_target: t, unwind: Some(ref u) }
@@ -188,7 +186,6 @@ pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
             | Call { target: None, cleanup: Some(ref mut t), .. }
             | Call { target: Some(ref mut t), cleanup: None, .. }
             | Yield { resume: ref mut t, drop: None, .. }
-            | DropAndReplace { target: ref mut t, unwind: None, .. }
             | Drop { target: ref mut t, unwind: None, .. }
             | Assert { target: ref mut t, cleanup: None, .. }
             | FalseUnwind { real_target: ref mut t, unwind: None }
@@ -198,7 +195,6 @@ pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
             }
             Call { target: Some(ref mut t), cleanup: Some(ref mut u), .. }
             | Yield { resume: ref mut t, drop: Some(ref mut u), .. }
-            | DropAndReplace { target: ref mut t, unwind: Some(ref mut u), .. }
             | Drop { target: ref mut t, unwind: Some(ref mut u), .. }
             | Assert { target: ref mut t, cleanup: Some(ref mut u), .. }
             | FalseUnwind { real_target: ref mut t, unwind: Some(ref mut u) }
@@ -225,7 +221,6 @@ pub fn unwind(&self) -> Option<&Option<BasicBlock>> {
             | TerminatorKind::FalseEdge { .. } => None,
             TerminatorKind::Call { cleanup: ref unwind, .. }
             | TerminatorKind::Assert { cleanup: ref unwind, .. }
-            | TerminatorKind::DropAndReplace { ref unwind, .. }
             | TerminatorKind::Drop { ref unwind, .. }
             | TerminatorKind::FalseUnwind { ref unwind, .. }
             | TerminatorKind::InlineAsm { cleanup: ref unwind, .. } => Some(unwind),
@@ -245,7 +240,6 @@ pub fn unwind_mut(&mut self) -> Option<&mut Option<BasicBlock>> {
             | TerminatorKind::FalseEdge { .. } => None,
             TerminatorKind::Call { cleanup: ref mut unwind, .. }
             | TerminatorKind::Assert { cleanup: ref mut unwind, .. }
-            | TerminatorKind::DropAndReplace { ref mut unwind, .. }
             | TerminatorKind::Drop { ref mut unwind, .. }
             | TerminatorKind::FalseUnwind { ref mut unwind, .. }
             | TerminatorKind::InlineAsm { cleanup: ref mut unwind, .. } => Some(unwind),
@@ -309,9 +303,6 @@ pub fn fmt_head<W: Write>(&self, fmt: &mut W) -> fmt::Result {
             Yield { value, resume_arg, .. } => write!(fmt, "{:?} = yield({:?})", resume_arg, value),
             Unreachable => write!(fmt, "unreachable"),
             Drop { place, .. } => write!(fmt, "drop({:?})", place),
-            DropAndReplace { place, value, .. } => {
-                write!(fmt, "replace({:?} <- {:?})", place, value)
-            }
             Call { func, args, destination, .. } => {
                 write!(fmt, "{:?} = ", destination)?;
                 write!(fmt, "{:?}(", func)?;
@@ -403,10 +394,10 @@ pub fn fmt_successor_labels(&self) -> Vec<Cow<'static, str>> {
             Call { target: None, cleanup: None, .. } => vec![],
             Yield { drop: Some(_), .. } => vec!["resume".into(), "drop".into()],
             Yield { drop: None, .. } => vec!["resume".into()],
-            DropAndReplace { unwind: None, .. } | Drop { unwind: None, .. } => {
+            Drop { unwind: None, .. } => {
                 vec!["return".into()]
             }
-            DropAndReplace { unwind: Some(_), .. } | Drop { unwind: Some(_), .. } => {
+            Drop { unwind: Some(_), .. } => {
                 vec!["return".into(), "unwind".into()]
             }
             Assert { cleanup: None, .. } => vec!["".into()],

compiler/rustc_middle/src/mir/visit.rs

@@ -495,20 +495,6 @@ fn super_terminator(&mut self,
                         );
                     }
 
-                    TerminatorKind::DropAndReplace {
-                        place,
-                        value,
-                        target: _,
-                        unwind: _,
-                    } => {
-                        self.visit_place(
-                            place,
-                            PlaceContext::MutatingUse(MutatingUseContext::Drop),
-                            location
-                        );
-                        self.visit_operand(value, location);
-                    }
-
                     TerminatorKind::Call {
                         func,
                         args,

compiler/rustc_mir_build/src/build/custom/parse/instruction.rs

@@ -58,14 +58,6 @@ pub fn parse_terminator(&self, expr_id: ExprId) -> PResult<TerminatorKind<'tcx>>
                     unwind: None,
                 })
             },
-            @call("mir_drop_and_replace", args) => {
-                Ok(TerminatorKind::DropAndReplace {
-                    place: self.parse_place(args[0])?,
-                    value: self.parse_operand(args[1])?,
-                    target: self.parse_block(args[2])?,
-                    unwind: None,
-                })
-            },
             @call("mir_call", args) => {
                 let destination = self.parse_place(args[0])?;
                 let target = self.parse_block(args[1])?;

compiler/rustc_mir_build/src/build/scope.rs

@@ -1072,7 +1072,6 @@ pub(crate) fn diverge_from(&mut self, start: BasicBlock) {
                 TerminatorKind::Assert { .. }
                     | TerminatorKind::Call { .. }
                     | TerminatorKind::Drop { .. }
-                    | TerminatorKind::DropAndReplace { .. }
                     | TerminatorKind::FalseUnwind { .. }
                     | TerminatorKind::InlineAsm { .. }
             ),
@@ -1432,8 +1431,7 @@ fn add_entry(cfg: &mut CFG<'tcx>, from: BasicBlock, to: BasicBlock) {
                     *unwind = Some(to);
                 }
             }
-            TerminatorKind::DropAndReplace { unwind, .. }
+            TerminatorKind::FalseUnwind { unwind, .. }
-            | TerminatorKind::FalseUnwind { unwind, .. }
             | TerminatorKind::Call { cleanup: unwind, .. }
             | TerminatorKind::Assert { cleanup: unwind, .. }
             | TerminatorKind::InlineAsm { cleanup: unwind, .. } => {

compiler/rustc_mir_build/src/lints.rs

@@ -128,7 +128,6 @@ fn node_examined(
             TerminatorKind::Assert { .. }
             | TerminatorKind::Call { .. }
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::FalseEdge { .. }
             | TerminatorKind::FalseUnwind { .. }
             | TerminatorKind::Goto { .. }

compiler/rustc_mir_dataflow/src/framework/direction.rs

@@ -480,7 +480,6 @@ fn join_state_into_successors_of<'tcx, A>(
 
             Assert { target, cleanup: unwind, expected: _, msg: _, cond: _ }
             | Drop { target, unwind, place: _ }
-            | DropAndReplace { target, unwind, value: _, place: _ }
             | FalseUnwind { real_target: target, unwind } => {
                 if let Some(unwind) = unwind {
                     propagate(unwind, exit_state);

compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs

@@ -111,8 +111,7 @@ fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Loc
         self.super_terminator(terminator, location);
 
         match terminator.kind {
-            mir::TerminatorKind::Drop { place: dropped_place, .. }
+            mir::TerminatorKind::Drop { place: dropped_place, .. } => {
-            | mir::TerminatorKind::DropAndReplace { place: dropped_place, .. } => {
                 // Drop terminators may call custom drop glue (`Drop::drop`), which takes `&mut
                 // self` as a parameter. In the general case, a drop impl could launder that
                 // reference into the surrounding environment through a raw pointer, thus creating

compiler/rustc_mir_dataflow/src/impls/storage_liveness.rs

@@ -202,7 +202,6 @@ fn before_terminator_effect(
             TerminatorKind::Abort
             | TerminatorKind::Assert { .. }
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::FalseEdge { .. }
             | TerminatorKind::FalseUnwind { .. }
             | TerminatorKind::GeneratorDrop
@@ -240,7 +239,6 @@ fn terminator_effect(
             | TerminatorKind::Abort
             | TerminatorKind::Assert { .. }
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::FalseEdge { .. }
             | TerminatorKind::FalseUnwind { .. }
             | TerminatorKind::GeneratorDrop

compiler/rustc_mir_dataflow/src/move_paths/builder.rs

@@ -392,11 +392,6 @@ fn gather_terminator(&mut self, term: &Terminator<'tcx>) {
                 self.create_move_path(place);
                 self.gather_init(place.as_ref(), InitKind::Deep);
             }
-            TerminatorKind::DropAndReplace { place, ref value, .. } => {
-                self.create_move_path(place);
-                self.gather_operand(value);
-                self.gather_init(place.as_ref(), InitKind::Deep);
-            }
             TerminatorKind::Call {
                 ref func,
                 ref args,

compiler/rustc_mir_dataflow/src/value_analysis.rs

@@ -230,7 +230,7 @@ fn super_terminator(&self, terminator: &Terminator<'tcx>, state: &mut State<Self
             TerminatorKind::Drop { place, .. } => {
                 state.flood_with(place.as_ref(), self.map(), Self::Value::bottom());
             }
-            TerminatorKind::DropAndReplace { .. } | TerminatorKind::Yield { .. } => {
+            TerminatorKind::Yield { .. } => {
                 // They would have an effect, but are not allowed in this phase.
                 bug!("encountered disallowed terminator");
             }

compiler/rustc_mir_transform/src/abort_unwinding_calls.rs

@@ -74,7 +74,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
                     };
                     layout::fn_can_unwind(tcx, fn_def_id, sig.abi())
                 }
-                TerminatorKind::Drop { .. } | TerminatorKind::DropAndReplace { .. } => {
+                TerminatorKind::Drop { .. } => {
                     tcx.sess.opts.unstable_opts.panic_in_drop == PanicStrategy::Unwind
                         && layout::fn_can_unwind(tcx, None, Abi::Rust)
                 }

compiler/rustc_mir_transform/src/add_moves_for_packed_drops.rs

@@ -64,9 +64,6 @@ fn add_moves_for_packed_drops_patch<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>)
             {
                 add_move_for_packed_drop(tcx, body, &mut patch, terminator, loc, data.is_cleanup);
             }
-            TerminatorKind::DropAndReplace { .. } => {
-                span_bug!(terminator.source_info.span, "replace in AddMovesForPackedDrops");
-            }
             _ => {}
         }
     }

compiler/rustc_mir_transform/src/add_retag.rs

@@ -100,7 +100,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
                     }
 
                     // `Drop` is also a call, but it doesn't return anything so we are good.
-                    TerminatorKind::Drop { .. } | TerminatorKind::DropAndReplace { .. } => None,
+                    TerminatorKind::Drop { .. } => None,
                     // Not a block ending in a Call -> ignore.
                     _ => None,
                 }

compiler/rustc_mir_transform/src/check_unsafety.rs

@@ -55,7 +55,6 @@ fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location
             | TerminatorKind::Drop { .. }
             | TerminatorKind::Yield { .. }
             | TerminatorKind::Assert { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::Resume
             | TerminatorKind::Abort

compiler/rustc_mir_transform/src/const_prop.rs

@@ -1007,7 +1007,6 @@ fn visit_terminator(&mut self, terminator: &mut Terminator<'tcx>, location: Loca
             | TerminatorKind::Return
             | TerminatorKind::Unreachable
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::Yield { .. }
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::FalseEdge { .. }

compiler/rustc_mir_transform/src/const_prop_lint.rs

@@ -686,7 +686,6 @@ fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             | TerminatorKind::Return
             | TerminatorKind::Unreachable
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::Yield { .. }
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::FalseEdge { .. }

compiler/rustc_mir_transform/src/coverage/debug.rs

@@ -822,7 +822,6 @@ pub(super) fn term_type(kind: &TerminatorKind<'_>) -> &'static str {
         TerminatorKind::Return => "Return",
         TerminatorKind::Unreachable => "Unreachable",
         TerminatorKind::Drop { .. } => "Drop",
-        TerminatorKind::DropAndReplace { .. } => "DropAndReplace",
         TerminatorKind::Call { .. } => "Call",
         TerminatorKind::Assert { .. } => "Assert",
         TerminatorKind::Yield { .. } => "Yield",

compiler/rustc_mir_transform/src/coverage/graph.rs

@@ -156,7 +156,6 @@ fn compute_basic_coverage_blocks(
                 | TerminatorKind::Resume
                 | TerminatorKind::Unreachable
                 | TerminatorKind::Drop { .. }
-                | TerminatorKind::DropAndReplace { .. }
                 | TerminatorKind::Call { .. }
                 | TerminatorKind::GeneratorDrop
                 | TerminatorKind::Assert { .. }

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -850,7 +850,6 @@ pub(super) fn filtered_terminator_span(terminator: &Terminator<'_>) -> Option<Sp
         TerminatorKind::Unreachable // Unreachable blocks are not connected to the MIR CFG
         | TerminatorKind::Assert { .. }
         | TerminatorKind::Drop { .. }
-        | TerminatorKind::DropAndReplace { .. }
         | TerminatorKind::SwitchInt { .. }
         // For `FalseEdge`, only the `real` branch is taken, so it is similar to a `Goto`.
         | TerminatorKind::FalseEdge { .. }

compiler/rustc_mir_transform/src/coverage/tests.rs

@@ -86,7 +86,6 @@ fn link(&mut self, from_block: BasicBlock, to_block: BasicBlock) {
             TerminatorKind::Assert { ref mut target, .. }
             | TerminatorKind::Call { target: Some(ref mut target), .. }
             | TerminatorKind::Drop { ref mut target, .. }
-            | TerminatorKind::DropAndReplace { ref mut target, .. }
             | TerminatorKind::FalseEdge { real_target: ref mut target, .. }
             | TerminatorKind::FalseUnwind { real_target: ref mut target, .. }
             | TerminatorKind::Goto { ref mut target }
@@ -184,7 +183,6 @@ fn debug_basic_blocks(mir_body: &Body<'_>) -> String {
                     TerminatorKind::Assert { target, .. }
                     | TerminatorKind::Call { target: Some(target), .. }
                     | TerminatorKind::Drop { target, .. }
-                    | TerminatorKind::DropAndReplace { target, .. }
                     | TerminatorKind::FalseEdge { real_target: target, .. }
                     | TerminatorKind::FalseUnwind { real_target: target, .. }
                     | TerminatorKind::Goto { target }

compiler/rustc_mir_transform/src/dest_prop.rs

@@ -650,8 +650,7 @@ fn for_terminator<'tcx>(&mut self, terminator: &TerminatorKind<'tcx>) {
             TerminatorKind::Drop { .. } => {
                 // `Drop`s create a `&mut` and so are not considered
             }
-            TerminatorKind::DropAndReplace { .. }
+            TerminatorKind::Yield { .. }
-            | TerminatorKind::Yield { .. }
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::FalseEdge { .. }
             | TerminatorKind::FalseUnwind { .. } => {

compiler/rustc_mir_transform/src/elaborate_drops.rs

@@ -18,15 +18,14 @@
 use rustc_target::abi::VariantIdx;
 use std::fmt;
 
-/// During MIR building, Drop and DropAndReplace terminators are inserted in every place where a drop may occur.
+/// During MIR building, Drop terminators are inserted in every place where a drop may occur.
 /// However, in this phase, the presence of these terminators does not guarantee that a destructor will run,
 /// as the target of the drop may be uninitialized.
 /// In general, the compiler cannot determine at compile time whether a destructor will run or not.
 ///
-/// At a high level, this pass refines Drop and DropAndReplace to only run the destructor if the
+/// At a high level, this pass refines Drop to only run the destructor if the
 /// target is initialized. The way this is achievied is by inserting drop flags for every variable
 /// that may be dropped, and then using those flags to determine whether a destructor should run.
-/// This pass also removes DropAndReplace, replacing it with a Drop paired with an assign statement.
 /// Once this is complete, Drop terminators in the MIR correspond to a call to the "drop glue" or
 /// "drop shim" for the type of the dropped place.
 ///
@@ -121,8 +120,7 @@ fn remove_dead_unwinds<'tcx>(
         .into_results_cursor(body);
     for (bb, bb_data) in body.basic_blocks.iter_enumerated() {
         let place = match bb_data.terminator().kind {
-            TerminatorKind::Drop { ref place, unwind: Some(_), .. }
+            TerminatorKind::Drop { ref place, unwind: Some(_), .. } => {
-            | TerminatorKind::DropAndReplace { ref place, unwind: Some(_), .. } => {
                 und.derefer(place.as_ref(), body).unwrap_or(*place)
             }
             _ => continue,
@@ -343,8 +341,7 @@ fn collect_drop_flags(&mut self) {
             }
             let terminator = data.terminator();
             let place = match terminator.kind {
-                TerminatorKind::Drop { ref place, .. }
+                TerminatorKind::Drop { ref place, .. } => {
-                | TerminatorKind::DropAndReplace { ref place, .. } => {
                     self.un_derefer.derefer(place.as_ref(), self.body).unwrap_or(*place)
                 }
                 _ => continue,
@@ -441,103 +438,11 @@ fn elaborate_drops(&mut self) {
                         }
                     }
                 }
-                TerminatorKind::DropAndReplace { mut place, ref value, target, unwind } => {
-                    assert!(!data.is_cleanup);
-
-                    if let Some(new_place) = self.un_derefer.derefer(place.as_ref(), self.body) {
-                        place = new_place;
-                    }
-                    self.elaborate_replace(loc, place, value, target, unwind);
-                }
                 _ => continue,
             }
         }
     }
 
-    /// Elaborate a MIR `replace` terminator. This instruction
-    /// is not directly handled by codegen, and therefore
-    /// must be desugared.
-    ///
-    /// The desugaring drops the location if needed, and then writes
-    /// the value (including setting the drop flag) over it in *both* arms.
-    ///
-    /// The `replace` terminator can also be called on places that
-    /// are not tracked by elaboration (for example,
-    /// `replace x[i] <- tmp0`). The borrow checker requires that
-    /// these locations are initialized before the assignment,
-    /// so we just generate an unconditional drop.
-    fn elaborate_replace(
-        &mut self,
-        loc: Location,
-        place: Place<'tcx>,
-        value: &Operand<'tcx>,
-        target: BasicBlock,
-        unwind: Option<BasicBlock>,
-    ) {
-        let bb = loc.block;
-        let data = &self.body[bb];
-        let terminator = data.terminator();
-        assert!(!data.is_cleanup, "DropAndReplace in unwind path not supported");
-
-        let assign = Statement {
-            kind: StatementKind::Assign(Box::new((place, Rvalue::Use(value.clone())))),
-            source_info: terminator.source_info,
-        };
-
-        let unwind = unwind.unwrap_or_else(|| self.patch.resume_block());
-        let unwind = self.patch.new_block(BasicBlockData {
-            statements: vec![assign.clone()],
-            terminator: Some(Terminator {
-                kind: TerminatorKind::Goto { target: unwind },
-                ..*terminator
-            }),
-            is_cleanup: true,
-        });
-
-        let target = self.patch.new_block(BasicBlockData {
-            statements: vec![assign],
-            terminator: Some(Terminator { kind: TerminatorKind::Goto { target }, ..*terminator }),
-            is_cleanup: false,
-        });
-
-        match self.move_data().rev_lookup.find(place.as_ref()) {
-            LookupResult::Exact(path) => {
-                debug!("elaborate_drop_and_replace({:?}) - tracked {:?}", terminator, path);
-                self.init_data.seek_before(loc);
-                elaborate_drop(
-                    &mut Elaborator { ctxt: self },
-                    terminator.source_info,
-                    place,
-                    path,
-                    target,
-                    Unwind::To(unwind),
-                    bb,
-                );
-                on_all_children_bits(self.tcx, self.body, self.move_data(), path, |child| {
-                    self.set_drop_flag(
-                        Location { block: target, statement_index: 0 },
-                        child,
-                        DropFlagState::Present,
-                    );
-                    self.set_drop_flag(
-                        Location { block: unwind, statement_index: 0 },
-                        child,
-                        DropFlagState::Present,
-                    );
-                });
-            }
-            LookupResult::Parent(parent) => {
-                // drop and replace behind a pointer/array/whatever. The location
-                // must be initialized.
-                debug!("elaborate_drop_and_replace({:?}) - untracked {:?}", terminator, parent);
-                self.patch.patch_terminator(
-                    bb,
-                    TerminatorKind::Drop { place, target, unwind: Some(unwind) },
-                );
-            }
-        }
-    }
-
     fn constant_bool(&self, span: Span, val: bool) -> Rvalue<'tcx> {
         Rvalue::Use(Operand::Constant(Box::new(Constant {
             span,
@@ -609,22 +514,12 @@ fn drop_flags_for_locs(&mut self) {
             debug!("drop_flags_for_locs({:?})", data);
             for i in 0..(data.statements.len() + 1) {
                 debug!("drop_flag_for_locs: stmt {}", i);
-                let mut allow_initializations = true;
                 if i == data.statements.len() {
                     match data.terminator().kind {
                         TerminatorKind::Drop { .. } => {
                             // drop elaboration should handle that by itself
                             continue;
                         }
-                        TerminatorKind::DropAndReplace { .. } => {
-                            // this contains the move of the source and
-                            // the initialization of the destination. We
-                            // only want the former - the latter is handled
-                            // by the elaboration code and must be done
-                            // *after* the destination is dropped.
-                            assert!(self.patch.is_patched(bb));
-                            allow_initializations = false;
-                        }
                         TerminatorKind::Resume => {
                             // It is possible for `Resume` to be patched
                             // (in particular it can be patched to be replaced with
@@ -641,11 +536,7 @@ fn drop_flags_for_locs(&mut self) {
                     self.body,
                     self.env,
                     loc,
-                    |path, ds| {
+                    |path, ds| self.set_drop_flag(loc, path, ds),
-                        if ds == DropFlagState::Absent || allow_initializations {
-                            self.set_drop_flag(loc, path, ds)
-                        }
-                    },
                 )
             }
 

compiler/rustc_mir_transform/src/generator.rs

@@ -1199,7 +1199,6 @@ fn can_unwind<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) -> bool {
 
             // These may unwind.
             TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::Call { .. }
             | TerminatorKind::InlineAsm { .. }
             | TerminatorKind::Assert { .. } => return true,
@@ -1691,7 +1690,6 @@ fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location
             | TerminatorKind::Return
             | TerminatorKind::Unreachable
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::Assert { .. }
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::FalseEdge { .. }

compiler/rustc_mir_transform/src/inline.rs

@@ -453,9 +453,7 @@ fn check_mir_body(
             checker.visit_basic_block_data(bb, blk);
 
             let term = blk.terminator();
-            if let TerminatorKind::Drop { ref place, target, unwind }
+            if let TerminatorKind::Drop { ref place, target, unwind } = term.kind {
-            | TerminatorKind::DropAndReplace { ref place, target, unwind, .. } = term.kind
-            {
                 work_list.push(target);
 
                 // If the place doesn't actually need dropping, treat it like a regular goto.
@@ -815,8 +813,7 @@ fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
     fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
         let tcx = self.tcx;
         match terminator.kind {
-            TerminatorKind::Drop { ref place, unwind, .. }
+            TerminatorKind::Drop { ref place, unwind, .. } => {
-            | TerminatorKind::DropAndReplace { ref place, unwind, .. } => {
                 // If the place doesn't actually need dropping, treat it like a regular goto.
                 let ty = self.instance.subst_mir(tcx, &place.ty(self.callee_body, tcx).ty);
                 if ty.needs_drop(tcx, self.param_env) {
@@ -1120,8 +1117,7 @@ fn visit_terminator(&mut self, terminator: &mut Terminator<'tcx>, loc: Location)
                     *tgt = self.map_block(*tgt);
                 }
             }
-            TerminatorKind::Drop { ref mut target, ref mut unwind, .. }
+            TerminatorKind::Drop { ref mut target, ref mut unwind, .. } => {
-            | TerminatorKind::DropAndReplace { ref mut target, ref mut unwind, .. } => {
                 *target = self.map_block(*target);
                 *unwind = self.map_unwind(*unwind);
             }

compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs

@@ -75,7 +75,6 @@ fn is_nop_landing_pad(
             | TerminatorKind::Unreachable
             | TerminatorKind::Call { .. }
             | TerminatorKind::Assert { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::Drop { .. }
             | TerminatorKind::InlineAsm { .. } => false,
         }

compiler/rustc_mir_transform/src/remove_uninit_drops.rs

@@ -1,5 +1,5 @@
 use rustc_index::bit_set::ChunkedBitSet;
-use rustc_middle::mir::{Body, Field, Rvalue, Statement, StatementKind, TerminatorKind};
+use rustc_middle::mir::{Body, Field, TerminatorKind};
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt, VariantDef};
 use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
@@ -8,7 +8,7 @@
 
 use crate::MirPass;
 
-/// Removes `Drop` and `DropAndReplace` terminators whose target is known to be uninitialized at
+/// Removes `Drop` terminators whose target is known to be uninitialized at
 /// that point.
 ///
 /// This is redundant with drop elaboration, but we need to do it prior to const-checking, and
@@ -37,8 +37,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let mut to_remove = vec![];
         for (bb, block) in body.basic_blocks.iter_enumerated() {
             let terminator = block.terminator();
-            let (TerminatorKind::Drop { place, .. } | TerminatorKind::DropAndReplace { place, .. })
+            let TerminatorKind::Drop { place, .. } = &terminator.kind
-                = &terminator.kind
             else { continue };
 
             maybe_inits.seek_before_primary_effect(body.terminator_loc(bb));
@@ -64,24 +63,12 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         for bb in to_remove {
             let block = &mut body.basic_blocks_mut()[bb];
 
-            let (TerminatorKind::Drop { target, .. } | TerminatorKind::DropAndReplace { target, .. })
+            let TerminatorKind::Drop { target, .. }
                 = &block.terminator().kind
             else { unreachable!() };
 
             // Replace block terminator with `Goto`.
-            let target = *target;
+            block.terminator_mut().kind = TerminatorKind::Goto { target: *target };
-            let old_terminator_kind = std::mem::replace(
-                &mut block.terminator_mut().kind,
-                TerminatorKind::Goto { target },
-            );
-
-            // If this is a `DropAndReplace`, we need to emulate the assignment to the return place.
-            if let TerminatorKind::DropAndReplace { place, value, .. } = old_terminator_kind {
-                block.statements.push(Statement {
-                    source_info: block.terminator().source_info,
-                    kind: StatementKind::Assign(Box::new((place, Rvalue::Use(value)))),
-                });
-            }
         }
     }
 }

compiler/rustc_mir_transform/src/separate_const_switch.rs

@@ -108,7 +108,6 @@ pub fn separate_const_switch(body: &mut Body<'_>) -> usize {
                         // The following terminators are not allowed
                         TerminatorKind::Resume
                         | TerminatorKind::Drop { .. }
-                        | TerminatorKind::DropAndReplace { .. }
                         | TerminatorKind::Call { .. }
                         | TerminatorKind::Assert { .. }
                         | TerminatorKind::FalseUnwind { .. }
@@ -170,7 +169,6 @@ pub fn separate_const_switch(body: &mut Body<'_>) -> usize {
             | TerminatorKind::Unreachable
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::Assert { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::FalseUnwind { .. }
             | TerminatorKind::Drop { .. }
             | TerminatorKind::Call { .. }

compiler/rustc_monomorphize/src/collector.rs

@@ -808,8 +808,7 @@ fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Loc
                 let callee_ty = self.monomorphize(callee_ty);
                 visit_fn_use(self.tcx, callee_ty, true, source, &mut self.output)
             }
-            mir::TerminatorKind::Drop { ref place, .. }
+            mir::TerminatorKind::Drop { ref place, .. } => {
-            | mir::TerminatorKind::DropAndReplace { ref place, .. } => {
                 let ty = place.ty(self.body, self.tcx).ty;
                 let ty = self.monomorphize(ty);
                 visit_drop_use(self.tcx, ty, true, source, self.output);

library/core/src/intrinsics/mir.rs

@@ -227,7 +227,7 @@
 //! are no resume and abort terminators, and terminators that might unwind do not have any way to
 //! indicate the unwind block.
 //!
-//!  - [`Goto`], [`Return`], [`Unreachable`], [`Drop`](Drop()), and [`DropAndReplace`] have associated functions.
+//!  - [`Goto`], [`Return`], [`Unreachable`] and [`Drop`](Drop()) have associated functions.
 //!  - `match some_int_operand` becomes a `SwitchInt`. Each arm should be `literal => basic_block`
 //!     - The exception is the last arm, which must be `_ => basic_block` and corresponds to the
 //!       otherwise branch.
@@ -259,7 +259,6 @@ pub fn $($sig)* { panic!() }
 define!("mir_goto", fn Goto(destination: BasicBlock) -> BasicBlock);
 define!("mir_unreachable", fn Unreachable() -> BasicBlock);
 define!("mir_drop", fn Drop<T>(place: T, goto: BasicBlock));
-define!("mir_drop_and_replace", fn DropAndReplace<T>(place: T, value: T, goto: BasicBlock));
 define!("mir_call", fn Call<T>(place: T, goto: BasicBlock, call: T));
 define!("mir_storage_live", fn StorageLive<T>(local: T));
 define!("mir_storage_dead", fn StorageDead<T>(local: T));

src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs

@@ -299,10 +299,6 @@ fn check_terminator<'tcx>(
         | TerminatorKind::Unreachable => Ok(()),
 
         TerminatorKind::Drop { place, .. } => check_place(tcx, *place, span, body),
-        TerminatorKind::DropAndReplace { place, value, .. } => {
-            check_place(tcx, *place, span, body)?;
-            check_operand(tcx, value, span, body)
-        },
 
         TerminatorKind::SwitchInt { discr, targets: _ } => check_operand(tcx, discr, span, body),
 

tests/mir-opt/building/custom/terminators.drop_first.built.after.mir

@@ -4,10 +4,11 @@ fn drop_first(_1: WriteOnDrop<'_>, _2: WriteOnDrop<'_>) -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/terminators.rs:+0:59: +0:59
 
     bb0: {
-        replace(_1 <- move _2) -> bb1;   // scope 0 at $DIR/terminators.rs:+3:13: +3:49
+        drop(_1) -> bb1;                 // scope 0 at $DIR/terminators.rs:+3:13: +3:30
     }
 
     bb1: {
-        return;                          // scope 0 at $DIR/terminators.rs:+7:13: +7:21
+        _1 = move _2;                    // scope 0 at $DIR/terminators.rs:+7:13: +7:24
+        return;                          // scope 0 at $DIR/terminators.rs:+8:13: +8:21
     }
 }

tests/mir-opt/building/custom/terminators.rs

@@ -48,10 +48,11 @@ fn drop(&mut self) {
 fn drop_first<'a>(a: WriteOnDrop<'a>, b: WriteOnDrop<'a>) {
     mir!(
         {
-            DropAndReplace(a, Move(b), retblock)
+            Drop(a, retblock)
         }
 
         retblock = {
+            a = Move(b);
             Return()
         }
     )