Auto merge of #107267 - cjgillot:keep-aggregate, r=oli-obk

Do not deaggregate MIR

This turns out to simplify a lot of things.
I haven't checked the consequences for miri yet.

cc `@JakobDegen`
r? `@oli-obk`

21 files changed, 130 insertions, 218 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 50c0faf4597..b0a8188e5e0 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -2645,6 +2645,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             operands,
                         ) = rvalue
                         {
+                            let def_id = def_id.expect_local();
                             for operand in operands {
                                 let (Operand::Copy(assigned_from) | Operand::Move(assigned_from)) = operand else {
                                     continue;
@@ -2667,7 +2668,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 // into a place then we should annotate the closure in
                                 // case it ends up being assigned into the return place.
                                 annotated_closure =
-                                    self.annotate_fn_sig(*def_id, substs.as_closure().sig());
+                                    self.annotate_fn_sig(def_id, substs.as_closure().sig());
                                 debug!(
                                     "annotate_argument_and_return_for_borrow: \
                                      annotated_closure={:?} assigned_from_local={:?} \
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 8c579bac7e8..a75ec87be4c 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -817,6 +817,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             && let AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) = **kind
         {
             debug!("move_spans: def_id={:?} places={:?}", def_id, places);
+            let def_id = def_id.expect_local();
             if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
                 self.closure_span(def_id, moved_place, places)
             {
@@ -945,6 +946,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     box AggregateKind::Generator(def_id, _, _) => (def_id, true),
                     _ => continue,
                 };
+                let def_id = def_id.expect_local();
 
                 debug!(
                     "borrow_spans: def_id={:?} is_generator={:?} places={:?}",
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index bc81abe4005..98103af779d 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -1278,6 +1278,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 // in order to populate our used_mut set.
                 match **aggregate_kind {
                     AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) => {
+                        let def_id = def_id.expect_local();
                         let BorrowCheckResult { used_mut_upvars, .. } =
                             self.infcx.tcx.mir_borrowck(def_id);
                         debug!("{:?} used_mut_upvars={:?}", def_id, used_mut_upvars);
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 6c67e1a00c3..5b52846562f 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2536,7 +2536,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             // clauses on the struct.
             AggregateKind::Closure(def_id, substs)
             | AggregateKind::Generator(def_id, substs, _) => {
-                (def_id.to_def_id(), self.prove_closure_bounds(tcx, def_id, substs, location))
+                (def_id, self.prove_closure_bounds(tcx, def_id.expect_local(), substs, location))
             }
 
             AggregateKind::Array(_) | AggregateKind::Tuple => {
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index 23196c8cbae..35948e50f48 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -13,6 +13,7 @@ use rustc_middle::ty::cast::{CastTy, IntTy};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
 use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
 use rustc_span::source_map::{Span, DUMMY_SP};
+use rustc_target::abi::VariantIdx;
 
 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     #[instrument(level = "trace", skip(self, bx))]
@@ -106,17 +107,16 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
 
             mir::Rvalue::Aggregate(ref kind, ref operands) => {
-                let (dest, active_field_index) = match **kind {
-                    mir::AggregateKind::Adt(adt_did, variant_index, _, _, active_field_index) => {
-                        dest.codegen_set_discr(bx, variant_index);
-                        if bx.tcx().adt_def(adt_did).is_enum() {
-                            (dest.project_downcast(bx, variant_index), active_field_index)
-                        } else {
-                            (dest, active_field_index)
-                        }
+                let (variant_index, variant_dest, active_field_index) = match **kind {
+                    mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
+                        let variant_dest = dest.project_downcast(bx, variant_index);
+                        (variant_index, variant_dest, active_field_index)
                     }
-                    _ => (dest, None),
+                    _ => (VariantIdx::from_u32(0), dest, None),
                 };
+                if active_field_index.is_some() {
+                    assert_eq!(operands.len(), 1);
+                }
                 for (i, operand) in operands.iter().enumerate() {
                     let op = self.codegen_operand(bx, operand);
                     // Do not generate stores and GEPis for zero-sized fields.
@@ -124,13 +124,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         let field_index = active_field_index.unwrap_or(i);
                         let field = if let mir::AggregateKind::Array(_) = **kind {
                             let llindex = bx.cx().const_usize(field_index as u64);
-                            dest.project_index(bx, llindex)
+                            variant_dest.project_index(bx, llindex)
                         } else {
-                            dest.project_field(bx, field_index)
+                            variant_dest.project_field(bx, field_index)
                         };
                         op.val.store(bx, field);
                     }
                 }
+                dest.codegen_set_discr(bx, variant_index);
             }
 
             _ => {
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index 274af61ee7c..8d4d0420cda 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -774,15 +774,6 @@ where
         variant_index: VariantIdx,
         dest: &PlaceTy<'tcx, M::Provenance>,
     ) -> InterpResult<'tcx> {
-        // This must be an enum or generator.
-        match dest.layout.ty.kind() {
-            ty::Adt(adt, _) => assert!(adt.is_enum()),
-            ty::Generator(..) => {}
-            _ => span_bug!(
-                self.cur_span(),
-                "write_discriminant called on non-variant-type (neither enum nor generator)"
-            ),
-        }
         // Layout computation excludes uninhabited variants from consideration
         // therefore there's no way to represent those variants in the given layout.
         // Essentially, uninhabited variants do not have a tag that corresponds to their
@@ -855,6 +846,34 @@ where
         Ok(())
     }
 
+    /// Writes the discriminant of the given variant.
+    #[instrument(skip(self), level = "debug")]
+    pub fn write_aggregate(
+        &mut self,
+        kind: &mir::AggregateKind<'tcx>,
+        operands: &[mir::Operand<'tcx>],
+        dest: &PlaceTy<'tcx, M::Provenance>,
+    ) -> InterpResult<'tcx> {
+        self.write_uninit(&dest)?;
+        let (variant_index, variant_dest, active_field_index) = match *kind {
+            mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
+                let variant_dest = self.place_downcast(&dest, variant_index)?;
+                (variant_index, variant_dest, active_field_index)
+            }
+            _ => (VariantIdx::from_u32(0), dest.clone(), None),
+        };
+        if active_field_index.is_some() {
+            assert_eq!(operands.len(), 1);
+        }
+        for (field_index, operand) in operands.iter().enumerate() {
+            let field_index = active_field_index.unwrap_or(field_index);
+            let field_dest = self.place_field(&variant_dest, field_index)?;
+            let op = self.eval_operand(operand, Some(field_dest.layout))?;
+            self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?;
+        }
+        self.write_discriminant(variant_index, &dest)
+    }
+
     pub fn raw_const_to_mplace(
         &self,
         raw: ConstAlloc<'tcx>,
diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index d101937fd74..7d9a98da08a 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/compiler/rustc_const_eval/src/interpret/step.rs
@@ -199,13 +199,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
 
             Aggregate(box ref kind, ref operands) => {
-                assert!(matches!(kind, mir::AggregateKind::Array(..)));
-
-                for (field_index, operand) in operands.iter().enumerate() {
-                    let op = self.eval_operand(operand, None)?;
-                    let field_dest = self.place_field(&dest, field_index)?;
-                    self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?;
-                }
+                self.write_aggregate(kind, operands, &dest)?;
             }
 
             Repeat(ref operand, _) => {
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/check.rs b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
index f47e3e86ebe..1a23b06d2e8 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
@@ -453,7 +453,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             Rvalue::Aggregate(kind, ..) => {
                 if let AggregateKind::Generator(def_id, ..) = kind.as_ref()
-                    && let Some(generator_kind @ hir::GeneratorKind::Async(..)) = self.tcx.generator_kind(def_id.to_def_id())
+                    && let Some(generator_kind @ hir::GeneratorKind::Async(..)) = self.tcx.generator_kind(def_id)
                 {
                     self.check_op(ops::Generator(generator_kind));
                 }
diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs
index 72f456138ef..76b316cdf0c 100644
--- a/compiler/rustc_const_eval/src/transform/validate.rs
+++ b/compiler/rustc_const_eval/src/transform/validate.rs
@@ -8,10 +8,10 @@ use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::visit::NonUseContext::VarDebugInfo;
 use rustc_middle::mir::visit::{PlaceContext, Visitor};
 use rustc_middle::mir::{
-    traversal, AggregateKind, BasicBlock, BinOp, Body, BorrowKind, CastKind, CopyNonOverlapping,
-    Local, Location, MirPass, MirPhase, NonDivergingIntrinsic, Operand, Place, PlaceElem, PlaceRef,
-    ProjectionElem, RetagKind, RuntimePhase, Rvalue, SourceScope, Statement, StatementKind,
-    Terminator, TerminatorKind, UnOp, START_BLOCK,
+    traversal, BasicBlock, BinOp, Body, BorrowKind, CastKind, CopyNonOverlapping, Local, Location,
+    MirPass, MirPhase, NonDivergingIntrinsic, Operand, Place, PlaceElem, PlaceRef, ProjectionElem,
+    RetagKind, RuntimePhase, Rvalue, SourceScope, Statement, StatementKind, Terminator,
+    TerminatorKind, UnOp, START_BLOCK,
 };
 use rustc_middle::ty::{self, InstanceDef, ParamEnv, Ty, TyCtxt};
 use rustc_mir_dataflow::impls::MaybeStorageLive;
@@ -423,19 +423,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             };
         }
         match rvalue {
-            Rvalue::Use(_) | Rvalue::CopyForDeref(_) => {}
-            Rvalue::Aggregate(agg_kind, _) => {
-                let disallowed = match **agg_kind {
-                    AggregateKind::Array(..) => false,
-                    _ => self.mir_phase >= MirPhase::Runtime(RuntimePhase::PostCleanup),
-                };
-                if disallowed {
-                    self.fail(
-                        location,
-                        format!("{:?} have been lowered to field assignments", rvalue),
-                    )
-                }
-            }
+            Rvalue::Use(_) | Rvalue::CopyForDeref(_) | Rvalue::Aggregate(..) => {}
             Rvalue::Ref(_, BorrowKind::Shallow, _) => {
                 if self.mir_phase >= MirPhase::Runtime(RuntimePhase::Initial) {
                     self.fail(
diff --git a/compiler/rustc_const_eval/src/util/aggregate.rs b/compiler/rustc_const_eval/src/util/aggregate.rs
deleted file mode 100644
index 10783c5ed1d..00000000000
--- a/compiler/rustc_const_eval/src/util/aggregate.rs
+++ /dev/null
@@ -1,77 +0,0 @@
-use rustc_index::vec::Idx;
-use rustc_middle::mir::*;
-use rustc_middle::ty::{Ty, TyCtxt};
-use rustc_target::abi::VariantIdx;
-
-use std::iter::TrustedLen;
-
-/// Expand `lhs = Rvalue::Aggregate(kind, operands)` into assignments to the fields.
-///
-/// Produces something like
-/// ```ignore (ilustrative)
-/// (lhs as Variant).field0 = arg0;     // We only have a downcast if this is an enum
-/// (lhs as Variant).field1 = arg1;
-/// discriminant(lhs) = variant_index;  // If lhs is an enum or generator.
-/// ```
-pub fn expand_aggregate<'tcx>(
-    orig_lhs: Place<'tcx>,
-    operands: impl Iterator<Item = (Operand<'tcx>, Ty<'tcx>)> + TrustedLen,
-    kind: AggregateKind<'tcx>,
-    source_info: SourceInfo,
-    tcx: TyCtxt<'tcx>,
-) -> impl Iterator<Item = Statement<'tcx>> + TrustedLen {
-    let mut lhs = orig_lhs;
-    let mut set_discriminant = None;
-    let active_field_index = match kind {
-        AggregateKind::Adt(adt_did, variant_index, _, _, active_field_index) => {
-            let adt_def = tcx.adt_def(adt_did);
-            if adt_def.is_enum() {
-                set_discriminant = Some(Statement {
-                    kind: StatementKind::SetDiscriminant {
-                        place: Box::new(orig_lhs),
-                        variant_index,
-                    },
-                    source_info,
-                });
-                lhs = tcx.mk_place_downcast(orig_lhs, adt_def, variant_index);
-            }
-            active_field_index
-        }
-        AggregateKind::Generator(..) => {
-            // Right now we only support initializing generators to
-            // variant 0 (Unresumed).
-            let variant_index = VariantIdx::new(0);
-            set_discriminant = Some(Statement {
-                kind: StatementKind::SetDiscriminant { place: Box::new(orig_lhs), variant_index },
-                source_info,
-            });
-
-            // Operands are upvars stored on the base place, so no
-            // downcast is necessary.
-
-            None
-        }
-        _ => None,
-    };
-
-    let operands = operands.enumerate().map(move |(i, (op, ty))| {
-        let lhs_field = if let AggregateKind::Array(_) = kind {
-            let offset = u64::try_from(i).unwrap();
-            tcx.mk_place_elem(
-                lhs,
-                ProjectionElem::ConstantIndex { offset, min_length: offset + 1, from_end: false },
-            )
-        } else {
-            let field = Field::new(active_field_index.unwrap_or(i));
-            tcx.mk_place_field(lhs, field, ty)
-        };
-        Statement {
-            source_info,
-            kind: StatementKind::Assign(Box::new((lhs_field, Rvalue::Use(op)))),
-        }
-    });
-    [Statement { source_info, kind: StatementKind::Deinit(Box::new(orig_lhs)) }]
-        .into_iter()
-        .chain(operands)
-        .chain(set_discriminant)
-}
diff --git a/compiler/rustc_const_eval/src/util/mod.rs b/compiler/rustc_const_eval/src/util/mod.rs
index 76ea5a24e69..51735e33e0f 100644
--- a/compiler/rustc_const_eval/src/util/mod.rs
+++ b/compiler/rustc_const_eval/src/util/mod.rs
@@ -1,4 +1,3 @@
-pub mod aggregate;
 mod alignment;
 mod call_kind;
 pub mod collect_writes;
@@ -7,7 +6,6 @@ mod find_self_call;
 mod might_permit_raw_init;
 mod type_name;
 
-pub use self::aggregate::expand_aggregate;
 pub use self::alignment::is_disaligned;
 pub use self::call_kind::{call_kind, CallDesugaringKind, CallKind};
 pub use self::compare_types::{is_equal_up_to_subtyping, is_subtype};
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 05a9ec5e6d0..10ac7e0d39a 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -2098,10 +2098,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                     AggregateKind::Closure(def_id, substs) => ty::tls::with(|tcx| {
                         let name = if tcx.sess.opts.unstable_opts.span_free_formats {
                             let substs = tcx.lift(substs).unwrap();
-                            format!(
-                                "[closure@{}]",
-                                tcx.def_path_str_with_substs(def_id.to_def_id(), substs),
-                            )
+                            format!("[closure@{}]", tcx.def_path_str_with_substs(def_id, substs),)
                         } else {
                             let span = tcx.def_span(def_id);
                             format!(
@@ -2112,11 +2109,17 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         let mut struct_fmt = fmt.debug_struct(&name);
 
                         // FIXME(project-rfc-2229#48): This should be a list of capture names/places
-                        if let Some(upvars) = tcx.upvars_mentioned(def_id) {
+                        if let Some(def_id) = def_id.as_local()
+                            && let Some(upvars) = tcx.upvars_mentioned(def_id)
+                        {
                             for (&var_id, place) in iter::zip(upvars.keys(), places) {
                                 let var_name = tcx.hir().name(var_id);
                                 struct_fmt.field(var_name.as_str(), place);
                             }
+                        } else {
+                            for (index, place) in places.iter().enumerate() {
+                                struct_fmt.field(&format!("{index}"), place);
+                            }
                         }
 
                         struct_fmt.finish()
@@ -2127,11 +2130,17 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         let mut struct_fmt = fmt.debug_struct(&name);
 
                         // FIXME(project-rfc-2229#48): This should be a list of capture names/places
-                        if let Some(upvars) = tcx.upvars_mentioned(def_id) {
+                        if let Some(def_id) = def_id.as_local()
+                            && let Some(upvars) = tcx.upvars_mentioned(def_id)
+                        {
                             for (&var_id, place) in iter::zip(upvars.keys(), places) {
                                 let var_name = tcx.hir().name(var_id);
                                 struct_fmt.field(var_name.as_str(), place);
                             }
+                        } else {
+                            for (index, place) in places.iter().enumerate() {
+                                struct_fmt.field(&format!("{index}"), place);
+                            }
                         }
 
                         struct_fmt.finish()
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 549bc65d6d7..66ee6818789 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -1203,10 +1203,8 @@ pub enum AggregateKind<'tcx> {
     /// active field index would identity the field `c`
     Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<usize>),
 
-    // Note: We can use LocalDefId since closures and generators a deaggregated
-    // before codegen.
-    Closure(LocalDefId, SubstsRef<'tcx>),
-    Generator(LocalDefId, SubstsRef<'tcx>, hir::Movability),
+    Closure(DefId, SubstsRef<'tcx>),
+    Generator(DefId, SubstsRef<'tcx>, hir::Movability),
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index 599f0b9d3fa..b5e0b88bbe5 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -205,9 +205,9 @@ impl<'tcx> Rvalue<'tcx> {
                 AggregateKind::Adt(did, _, substs, _, _) => {
                     tcx.bound_type_of(did).subst(tcx, substs)
                 }
-                AggregateKind::Closure(did, substs) => tcx.mk_closure(did.to_def_id(), substs),
+                AggregateKind::Closure(did, substs) => tcx.mk_closure(did, substs),
                 AggregateKind::Generator(did, substs, movability) => {
-                    tcx.mk_generator(did.to_def_id(), substs, movability)
+                    tcx.mk_generator(did, substs, movability)
                 }
             },
             Rvalue::ShallowInitBox(_, ty) => tcx.mk_box(ty),
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
index c7b3eb44dc5..cd0e6932863 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
@@ -439,10 +439,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         // We implicitly set the discriminant to 0. See
                         // librustc_mir/transform/deaggregator.rs for details.
                         let movability = movability.unwrap();
-                        Box::new(AggregateKind::Generator(closure_id, substs, movability))
+                        Box::new(AggregateKind::Generator(
+                            closure_id.to_def_id(),
+                            substs,
+                            movability,
+                        ))
                     }
                     UpvarSubsts::Closure(substs) => {
-                        Box::new(AggregateKind::Closure(closure_id, substs))
+                        Box::new(AggregateKind::Closure(closure_id.to_def_id(), substs))
                     }
                 };
                 block.and(Rvalue::Aggregate(result, operands))
diff --git a/compiler/rustc_mir_transform/src/check_unsafety.rs b/compiler/rustc_mir_transform/src/check_unsafety.rs
index 8afa53313fc..d00ee1f4bab 100644
--- a/compiler/rustc_mir_transform/src/check_unsafety.rs
+++ b/compiler/rustc_mir_transform/src/check_unsafety.rs
@@ -126,6 +126,7 @@ impl<'tcx> Visitor<'tcx> for UnsafetyChecker<'_, 'tcx> {
                     }
                 }
                 &AggregateKind::Closure(def_id, _) | &AggregateKind::Generator(def_id, _, _) => {
+                    let def_id = def_id.expect_local();
                     let UnsafetyCheckResult { violations, used_unsafe_blocks, .. } =
                         self.tcx.unsafety_check_result(def_id);
                     self.register_violations(violations, used_unsafe_blocks.iter().copied());
diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
index c75fe2327de..949a59a97bf 100644
--- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
+++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
@@ -5,6 +5,7 @@
 use rustc_const_eval::const_eval::CheckAlignment;
 use rustc_const_eval::interpret::{ConstValue, ImmTy, Immediate, InterpCx, Scalar};
 use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def::DefKind;
 use rustc_middle::mir::visit::{MutVisitor, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -85,6 +86,30 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'tcx> {
         state: &mut State<Self::Value>,
     ) {
         match rvalue {
+            Rvalue::Aggregate(kind, operands) => {
+                let target = self.map().find(target.as_ref());
+                if let Some(target) = target {
+                    state.flood_idx_with(target, self.map(), FlatSet::Bottom);
+                    let field_based = match **kind {
+                        AggregateKind::Tuple | AggregateKind::Closure(..) => true,
+                        AggregateKind::Adt(def_id, ..) => {
+                            matches!(self.tcx.def_kind(def_id), DefKind::Struct)
+                        }
+                        _ => false,
+                    };
+                    if field_based {
+                        for (field_index, operand) in operands.iter().enumerate() {
+                            if let Some(field) = self
+                                .map()
+                                .apply(target, TrackElem::Field(Field::from_usize(field_index)))
+                            {
+                                let result = self.handle_operand(operand, state);
+                                state.assign_idx(field, result, self.map());
+                            }
+                        }
+                    }
+                }
+            }
             Rvalue::CheckedBinaryOp(op, box (left, right)) => {
                 let target = self.map().find(target.as_ref());
                 if let Some(target) = target {
diff --git a/compiler/rustc_mir_transform/src/deaggregator.rs b/compiler/rustc_mir_transform/src/deaggregator.rs
deleted file mode 100644
index fe272de20f8..00000000000
--- a/compiler/rustc_mir_transform/src/deaggregator.rs
+++ /dev/null
@@ -1,45 +0,0 @@
-use crate::util::expand_aggregate;
-use crate::MirPass;
-use rustc_middle::mir::*;
-use rustc_middle::ty::TyCtxt;
-
-pub struct Deaggregator;
-
-impl<'tcx> MirPass<'tcx> for Deaggregator {
-    fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        let basic_blocks = body.basic_blocks.as_mut_preserves_cfg();
-        for bb in basic_blocks {
-            bb.expand_statements(|stmt| {
-                // FIXME(eddyb) don't match twice on `stmt.kind` (post-NLL).
-                match stmt.kind {
-                    // FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
-                    StatementKind::Assign(box (
-                        _,
-                        Rvalue::Aggregate(box AggregateKind::Array(_), _),
-                    )) => {
-                        return None;
-                    }
-                    StatementKind::Assign(box (_, Rvalue::Aggregate(_, _))) => {}
-                    _ => return None,
-                }
-
-                let stmt = stmt.replace_nop();
-                let source_info = stmt.source_info;
-                let StatementKind::Assign(box (lhs, Rvalue::Aggregate(kind, operands))) = stmt.kind else {
-                    bug!();
-                };
-
-                Some(expand_aggregate(
-                    lhs,
-                    operands.into_iter().map(|op| {
-                        let ty = op.ty(&body.local_decls, tcx);
-                        (op, ty)
-                    }),
-                    *kind,
-                    source_info,
-                    tcx,
-                ))
-            });
-        }
-    }
-}
diff --git a/compiler/rustc_mir_transform/src/generator.rs b/compiler/rustc_mir_transform/src/generator.rs
index 5624e312da1..47f9d35a4f7 100644
--- a/compiler/rustc_mir_transform/src/generator.rs
+++ b/compiler/rustc_mir_transform/src/generator.rs
@@ -52,7 +52,6 @@
 
 use crate::deref_separator::deref_finder;
 use crate::simplify;
-use crate::util::expand_aggregate;
 use crate::MirPass;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_errors::pluralize;
@@ -272,31 +271,26 @@ impl<'tcx> TransformVisitor<'tcx> {
             assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
 
             // FIXME(swatinem): assert that `val` is indeed unit?
-            statements.extend(expand_aggregate(
-                Place::return_place(),
-                std::iter::empty(),
-                kind,
+            statements.push(Statement {
+                kind: StatementKind::Assign(Box::new((
+                    Place::return_place(),
+                    Rvalue::Aggregate(Box::new(kind), vec![]),
+                ))),
                 source_info,
-                self.tcx,
-            ));
+            });
             return;
         }
 
         // else: `Poll::Ready(x)`, `GeneratorState::Yielded(x)` or `GeneratorState::Complete(x)`
         assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 1);
 
-        let ty = self
-            .tcx
-            .bound_type_of(self.state_adt_ref.variant(idx).fields[0].did)
-            .subst(self.tcx, self.state_substs);
-
-        statements.extend(expand_aggregate(
-            Place::return_place(),
-            std::iter::once((val, ty)),
-            kind,
+        statements.push(Statement {
+            kind: StatementKind::Assign(Box::new((
+                Place::return_place(),
+                Rvalue::Aggregate(Box::new(kind), vec![val]),
+            ))),
             source_info,
-            self.tcx,
-        ));
+        });
     }
 
     // Create a Place referencing a generator struct field
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 6815289776e..9070a7368b1 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -60,7 +60,6 @@ mod coverage;
 mod ctfe_limit;
 mod dataflow_const_prop;
 mod dead_store_elimination;
-mod deaggregator;
 mod deduce_param_attrs;
 mod deduplicate_blocks;
 mod deref_separator;
@@ -523,9 +522,6 @@ fn run_runtime_lowering_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         &elaborate_box_derefs::ElaborateBoxDerefs,
         &generator::StateTransform,
         &add_retag::AddRetag,
-        // Deaggregator is necessary for const prop. We may want to consider implementing
-        // CTFE support for aggregates.
-        &deaggregator::Deaggregator,
         &Lint(const_prop_lint::ConstProp),
     ];
     pm::run_passes_no_validate(tcx, body, passes, Some(MirPhase::Runtime(RuntimePhase::Initial)));
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index e9ca6f7c93c..551422386f6 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -15,7 +15,6 @@ use rustc_target::spec::abi::Abi;
 use std::fmt;
 use std::iter;
 
-use crate::util::expand_aggregate;
 use crate::{
     abort_unwinding_calls, add_call_guards, add_moves_for_packed_drops, deref_separator,
     pass_manager as pm, remove_noop_landing_pads, simplify,
@@ -831,19 +830,23 @@ pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> Body<'_> {
     // return;
     debug!("build_ctor: variant_index={:?}", variant_index);
 
-    let statements = expand_aggregate(
-        Place::return_place(),
-        adt_def.variant(variant_index).fields.iter().enumerate().map(|(idx, field_def)| {
-            (Operand::Move(Place::from(Local::new(idx + 1))), field_def.ty(tcx, substs))
-        }),
-        AggregateKind::Adt(adt_def.did(), variant_index, substs, None, None),
+    let kind = AggregateKind::Adt(adt_def.did(), variant_index, substs, None, None);
+    let variant = adt_def.variant(variant_index);
+    let statement = Statement {
+        kind: StatementKind::Assign(Box::new((
+            Place::return_place(),
+            Rvalue::Aggregate(
+                Box::new(kind),
+                (0..variant.fields.len())
+                    .map(|idx| Operand::Move(Place::from(Local::new(idx + 1))))
+                    .collect(),
+            ),
+        ))),
         source_info,
-        tcx,
-    )
-    .collect();
+    };
 
     let start_block = BasicBlockData {
-        statements,
+        statements: vec![statement],
         terminator: Some(Terminator { source_info, kind: TerminatorKind::Return }),
         is_cleanup: false,
     };