Remove ShallowInitBox.

compiler/rustc_borrowck/src/lib.rs

@@ -1544,8 +1544,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
             Rvalue::Use(operand)
             | Rvalue::Repeat(operand, _)
             | Rvalue::UnaryOp(_ /*un_op*/, operand)
-            | Rvalue::Cast(_ /*cast_kind*/, operand, _ /*ty*/)
-            | Rvalue::ShallowInitBox(operand, _ /*ty*/) => {
+            | Rvalue::Cast(_ /*cast_kind*/, operand, _ /*ty*/) => {
                 self.consume_operand(location, (operand, span), state)
             }
 

compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs

@@ -297,8 +297,9 @@ impl<'a, 'tcx> LoanInvalidationsGenerator<'a, 'tcx> {
             Rvalue::Use(operand)
             | Rvalue::Repeat(operand, _)
             | Rvalue::UnaryOp(_ /*un_op*/, operand)
-            | Rvalue::Cast(_ /*cast_kind*/, operand, _ /*ty*/)
-            | Rvalue::ShallowInitBox(operand, _ /*ty*/) => self.consume_operand(location, operand),
+            | Rvalue::Cast(_ /*cast_kind*/, operand, _ /*ty*/) => {
+                self.consume_operand(location, operand)
+            }
 
             &Rvalue::Discriminant(place) => {
                 self.access_place(

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1004,17 +1004,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                 }
             }
 
-            Rvalue::ShallowInitBox(_operand, ty) => {
-                let trait_ref =
-                    ty::TraitRef::new(tcx, tcx.require_lang_item(LangItem::Sized, span), [*ty]);
-
-                self.prove_trait_ref(
-                    trait_ref,
-                    location.to_locations(),
-                    ConstraintCategory::SizedBound,
-                );
-            }
-
             Rvalue::Cast(cast_kind, op, ty) => {
                 match *cast_kind {
                     CastKind::PointerCoercion(
@@ -2231,7 +2220,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             | Rvalue::Ref(..)
             | Rvalue::RawPtr(..)
             | Rvalue::Cast(..)
-            | Rvalue::ShallowInitBox(..)
             | Rvalue::BinaryOp(..)
             | Rvalue::CopyForDeref(..)
             | Rvalue::UnaryOp(..)

compiler/rustc_codegen_cranelift/src/base.rs

@@ -902,7 +902,6 @@ fn codegen_stmt<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, cur_block: Block, stmt:
                     lval.write_cvalue_transmute(fx, operand);
                 }
                 Rvalue::CopyForDeref(_) => bug!("`CopyForDeref` in codegen"),
-                Rvalue::ShallowInitBox(..) => bug!("`ShallowInitBox` in codegen"),
             }
         }
         StatementKind::StorageLive(_)

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -710,7 +710,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 OperandRef { val: operand.val, layout, move_annotation: None }
             }
             mir::Rvalue::CopyForDeref(_) => bug!("`CopyForDeref` in codegen"),
-            mir::Rvalue::ShallowInitBox(..) => bug!("`ShallowInitBox` in codegen"),
         }
     }
 

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -646,8 +646,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             Rvalue::Cast(_, _, _) => {}
 
-            Rvalue::ShallowInitBox(_, _) => {}
-
             Rvalue::UnaryOp(op, operand) => {
                 let ty = operand.ty(self.body, self.tcx);
                 match op {

compiler/rustc_const_eval/src/check_consts/qualifs.rs

@@ -237,8 +237,7 @@ where
         Rvalue::Use(operand)
         | Rvalue::Repeat(operand, _)
         | Rvalue::UnaryOp(_, operand)
-        | Rvalue::Cast(_, operand, _)
-        | Rvalue::ShallowInitBox(operand, _) => in_operand::<Q, _>(cx, in_local, operand),
+        | Rvalue::Cast(_, operand, _) => in_operand::<Q, _>(cx, in_local, operand),
 
         Rvalue::BinaryOp(_, box (lhs, rhs)) => {
             in_operand::<Q, _>(cx, in_local, lhs) || in_operand::<Q, _>(cx, in_local, rhs)

compiler/rustc_const_eval/src/check_consts/resolver.rs

@@ -192,7 +192,6 @@ where
             }
 
             mir::Rvalue::Cast(..)
-            | mir::Rvalue::ShallowInitBox(..)
             | mir::Rvalue::Use(..)
             | mir::Rvalue::CopyForDeref(..)
             | mir::Rvalue::ThreadLocalRef(..)

compiler/rustc_const_eval/src/interpret/step.rs

@@ -249,12 +249,6 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 self.write_immediate(*val, &dest)?;
             }
 
-            ShallowInitBox(ref operand, _) => {
-                let src = self.eval_operand(operand, None)?;
-                let v = self.read_immediate(&src)?;
-                self.write_immediate(*v, &dest)?;
-            }
-
             Cast(cast_kind, ref operand, cast_ty) => {
                 let src = self.eval_operand(operand, None)?;
                 let cast_ty =

compiler/rustc_middle/src/mir/pretty.rs

@@ -1237,10 +1237,6 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                 }
             }
 
-            ShallowInitBox(ref place, ref ty) => {
-                with_no_trimmed_paths!(write!(fmt, "ShallowInitBox({place:?}, {ty})"))
-            }
-
             WrapUnsafeBinder(ref op, ty) => {
                 with_no_trimmed_paths!(write!(fmt, "wrap_binder!({op:?}; {ty})"))
             }

compiler/rustc_middle/src/mir/statement.rs

@@ -747,11 +747,6 @@ impl<'tcx> ConstOperand<'tcx> {
 ///////////////////////////////////////////////////////////////////////////
 // Rvalues
 
-pub enum RvalueInitializationState {
-    Shallow,
-    Deep,
-}
-
 impl<'tcx> Rvalue<'tcx> {
     /// Returns true if rvalue can be safely removed when the result is unused.
     #[inline]
@@ -786,7 +781,6 @@ impl<'tcx> Rvalue<'tcx> {
             | Rvalue::UnaryOp(_, _)
             | Rvalue::Discriminant(_)
             | Rvalue::Aggregate(_, _)
-            | Rvalue::ShallowInitBox(_, _)
             | Rvalue::WrapUnsafeBinder(_, _) => true,
         }
     }
@@ -833,21 +827,10 @@ impl<'tcx> Rvalue<'tcx> {
                 }
                 AggregateKind::RawPtr(ty, mutability) => Ty::new_ptr(tcx, ty, mutability),
             },
-            Rvalue::ShallowInitBox(_, ty) => Ty::new_box(tcx, ty),
             Rvalue::CopyForDeref(ref place) => place.ty(local_decls, tcx).ty,
             Rvalue::WrapUnsafeBinder(_, ty) => ty,
         }
     }
-
-    #[inline]
-    /// Returns `true` if this rvalue is deeply initialized (most rvalues) or
-    /// whether its only shallowly initialized (`Rvalue::Box`).
-    pub fn initialization_state(&self) -> RvalueInitializationState {
-        match *self {
-            Rvalue::ShallowInitBox(_, _) => RvalueInitializationState::Shallow,
-            _ => RvalueInitializationState::Deep,
-        }
-    }
 }
 
 impl BorrowKind {

compiler/rustc_middle/src/mir/syntax.rs

@@ -1458,13 +1458,6 @@ pub enum Rvalue<'tcx> {
     /// coroutine lowering, `Coroutine` aggregate kinds are disallowed too.
     Aggregate(Box<AggregateKind<'tcx>>, IndexVec<FieldIdx, Operand<'tcx>>),
 
-    /// Transmutes a `*mut u8` into shallow-initialized `Box<T>`.
-    ///
-    /// This is different from a normal transmute because dataflow analysis will treat the box as
-    /// 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)

compiler/rustc_middle/src/mir/visit.rs

@@ -810,11 +810,6 @@ macro_rules! make_mir_visitor {
                         }
                     }
 
-                    Rvalue::ShallowInitBox(operand, ty) => {
-                        self.visit_operand(operand, location);
-                        self.visit_ty($(& $mutability)? *ty, TyContext::Location(location));
-                    }
-
                     Rvalue::WrapUnsafeBinder(op, ty) => {
                         self.visit_operand(op, location);
                         self.visit_ty($(& $mutability)? *ty, TyContext::Location(location));

compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs

@@ -86,7 +86,6 @@ where
 
             Rvalue::Cast(..)
             | Rvalue::Ref(_, BorrowKind::Fake(_), _)
-            | Rvalue::ShallowInitBox(..)
             | Rvalue::Use(..)
             | Rvalue::ThreadLocalRef(..)
             | Rvalue::Repeat(..)

compiler/rustc_mir_dataflow/src/move_paths/builder.rs

@@ -391,15 +391,7 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             }
             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.tcx.mk_place_deref(*place));
-                    self.gather_init(place.as_ref(), InitKind::Shallow);
-                } else {
-                    self.gather_init(place.as_ref(), InitKind::Deep);
-                }
+                self.gather_init(place.as_ref(), InitKind::Deep);
                 self.gather_rvalue(rval);
             }
             StatementKind::FakeRead(box (_, place)) => {
@@ -435,7 +427,6 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             Rvalue::Use(ref operand)
             | Rvalue::Repeat(ref operand, _)
             | Rvalue::Cast(_, ref operand, _)
-            | Rvalue::ShallowInitBox(ref operand, _)
             | Rvalue::UnaryOp(_, ref operand)
             | Rvalue::WrapUnsafeBinder(ref operand, _) => self.gather_operand(operand),
             Rvalue::BinaryOp(ref _binop, box (ref lhs, ref rhs)) => {

compiler/rustc_mir_transform/src/dataflow_const_prop.rs

@@ -467,7 +467,6 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
             Rvalue::Discriminant(place) => state.get_discr(place.as_ref(), &self.map),
             Rvalue::Use(operand) => return self.handle_operand(operand, state),
             Rvalue::CopyForDeref(_) => bug!("`CopyForDeref` in runtime MIR"),
-            Rvalue::ShallowInitBox(..) => bug!("`ShallowInitBox` in runtime MIR"),
             Rvalue::Ref(..) | Rvalue::RawPtr(..) => {
                 // We don't track such places.
                 return ValueOrPlace::TOP;

compiler/rustc_mir_transform/src/elaborate_box_derefs.rs

@@ -1,12 +1,8 @@
 //! This pass transforms derefs of Box into a deref of the pointer inside Box.
 //!
 //! Box is not actually a pointer so it is incorrect to dereference it directly.
-//!
-//! `ShallowInitBox` being a device for drop elaboration to understand deferred assignment to box
-//! contents, we do not need this any more on runtime MIR.
 
-use rustc_abi::{FieldIdx, VariantIdx};
-use rustc_index::{IndexVec, indexvec};
+use rustc_abi::FieldIdx;
 use rustc_middle::mir::visit::MutVisitor;
 use rustc_middle::mir::*;
 use rustc_middle::span_bug;
@@ -89,68 +85,6 @@ impl<'a, 'tcx> MutVisitor<'tcx> for ElaborateBoxDerefVisitor<'a, 'tcx> {
 
         self.super_place(place, context, location);
     }
-
-    fn visit_statement(&mut self, stmt: &mut Statement<'tcx>, location: Location) {
-        self.super_statement(stmt, location);
-
-        let tcx = self.tcx;
-        let source_info = stmt.source_info;
-
-        if let StatementKind::Assign(box (_, ref mut rvalue)) = stmt.kind
-            && let Rvalue::ShallowInitBox(ref mut mutptr_to_u8, pointee) = *rvalue
-            && let ty::Adt(box_adt, box_args) = Ty::new_box(tcx, pointee).kind()
-        {
-            let args = tcx.mk_args(&[pointee.into()]);
-            let (unique_ty, nonnull_ty, ptr_ty) =
-                build_ptr_tys(tcx, pointee, self.unique_def, self.nonnull_def);
-            let adt_kind = |def: ty::AdtDef<'tcx>, args| {
-                Box::new(AggregateKind::Adt(def.did(), VariantIdx::ZERO, args, None, None))
-            };
-            let zst = |ty| {
-                Operand::Constant(Box::new(ConstOperand {
-                    span: source_info.span,
-                    user_ty: None,
-                    const_: Const::zero_sized(ty),
-                }))
-            };
-
-            let constptr = self.patch.new_temp(ptr_ty, source_info.span);
-            self.patch.add_assign(
-                location,
-                constptr.into(),
-                Rvalue::Cast(CastKind::Transmute, mutptr_to_u8.clone(), ptr_ty),
-            );
-
-            let nonnull = self.patch.new_temp(nonnull_ty, source_info.span);
-            self.patch.add_assign(
-                location,
-                nonnull.into(),
-                Rvalue::Aggregate(
-                    adt_kind(self.nonnull_def, args),
-                    indexvec![Operand::Move(constptr.into())],
-                ),
-            );
-
-            let unique = self.patch.new_temp(unique_ty, source_info.span);
-            let phantomdata_ty =
-                self.unique_def.non_enum_variant().fields[FieldIdx::ONE].ty(tcx, args);
-            self.patch.add_assign(
-                location,
-                unique.into(),
-                Rvalue::Aggregate(
-                    adt_kind(self.unique_def, args),
-                    indexvec![Operand::Move(nonnull.into()), zst(phantomdata_ty)],
-                ),
-            );
-
-            let global_alloc_ty =
-                box_adt.non_enum_variant().fields[FieldIdx::ONE].ty(tcx, box_args);
-            *rvalue = Rvalue::Aggregate(
-                adt_kind(*box_adt, box_args),
-                indexvec![Operand::Move(unique.into()), zst(global_alloc_ty)],
-            );
-        }
-    }
 }
 
 pub(super) struct ElaborateBoxDerefs;

compiler/rustc_mir_transform/src/gvn.rs

@@ -1069,7 +1069,7 @@ impl<'body, 'a, 'tcx> VnState<'body, 'a, 'tcx> {
 
             // Unsupported values.
             Rvalue::ThreadLocalRef(..) => return None,
-            Rvalue::CopyForDeref(_) | Rvalue::ShallowInitBox(..) => {
+            Rvalue::CopyForDeref(_) => {
                 bug!("forbidden in runtime MIR: {rvalue:?}")
             }
         };

compiler/rustc_mir_transform/src/known_panics_lint.rs

@@ -443,7 +443,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             | Rvalue::CopyForDeref(..)
             | Rvalue::Repeat(..)
             | Rvalue::Cast(..)
-            | Rvalue::ShallowInitBox(..)
             | Rvalue::Discriminant(..)
             | Rvalue::WrapUnsafeBinder(..) => {}
         }
@@ -605,8 +604,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
 
             Ref(..) | RawPtr(..) => return None,
 
-            ShallowInitBox(..) => return None,
-
             Cast(ref kind, ref value, to) => match kind {
                 CastKind::IntToInt | CastKind::IntToFloat => {
                     let value = self.eval_operand(value)?;

compiler/rustc_mir_transform/src/lint.rs

@@ -85,7 +85,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Lint<'a, 'tcx> {
                     | Rvalue::Repeat(..)
                     | Rvalue::Aggregate(..)
                     | Rvalue::Cast(..)
-                    | Rvalue::ShallowInitBox(..)
                     | Rvalue::WrapUnsafeBinder(..) => true,
                     Rvalue::ThreadLocalRef(..)
                     | Rvalue::UnaryOp(..)

compiler/rustc_mir_transform/src/promote_consts.rs

@@ -449,8 +449,6 @@ impl<'tcx> Validator<'_, 'tcx> {
                 self.validate_operand(operand)?;
             }
 
-            Rvalue::ShallowInitBox(_, _) => return Err(Unpromotable),
-
             Rvalue::UnaryOp(op, operand) => {
                 match op {
                     // These operations can never fail.

compiler/rustc_mir_transform/src/validate.rs

@@ -1259,14 +1259,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     }
                 }
             }
-            Rvalue::ShallowInitBox(operand, _) => {
-                if self.body.phase >= MirPhase::Runtime(RuntimePhase::Initial) {
-                    self.fail(location, format!("ShallowInitBox after ElaborateBoxDerefs"))
-                }
-
-                let a = operand.ty(&self.body.local_decls, self.tcx);
-                check_kinds!(a, "Cannot shallow init type {:?}", ty::RawPtr(..));
-            }
             Rvalue::Cast(kind, operand, target_type) => {
                 let op_ty = operand.ty(self.body, self.tcx);
                 match kind {

compiler/rustc_public/src/mir/body.rs

@@ -567,13 +567,6 @@ pub enum Rvalue {
     /// [#74836]: https://github.com/rust-lang/rust/issues/74836
     Repeat(Operand, TyConst),
 
-    /// Transmutes a `*mut u8` into shallow-initialized `Box<T>`.
-    ///
-    /// This is different from a normal transmute because dataflow analysis will treat the box as
-    /// initialized but its content as uninitialized. Like other pointer casts, this in general
-    /// affects alias analysis.
-    ShallowInitBox(Operand, Ty),
-
     /// Creates a pointer/reference to the given thread local.
     ///
     /// The yielded type is a `*mut T` if the static is mutable, otherwise if the static is extern a
@@ -651,7 +644,6 @@ impl Rvalue {
                 }
                 AggregateKind::RawPtr(ty, mutability) => Ok(Ty::new_ptr(ty, mutability)),
             },
-            Rvalue::ShallowInitBox(_, ty) => Ok(Ty::new_box(*ty)),
             Rvalue::CopyForDeref(place) => place.ty(locals),
         }
     }

compiler/rustc_public/src/mir/pretty.rs

@@ -383,7 +383,6 @@ fn pretty_rvalue<W: Write>(writer: &mut W, rval: &Rvalue) -> io::Result<()> {
         Rvalue::Repeat(op, cnst) => {
             write!(writer, "[{}; {}]", pretty_operand(op), pretty_ty_const(cnst))
         }
-        Rvalue::ShallowInitBox(_, _) => Ok(()),
         Rvalue::ThreadLocalRef(item) => {
             write!(writer, "thread_local_ref{item:?}")
         }