Auto merge of #115759 - oli-obk:open_drop_from_non-ADT, r=lcnr

Reveal opaque types before drop elaboration

fixes #113594

r? `@cjgillot`

cc `@JakobDegen`

This pass was introduced in #110714

I moved it before drop elaboration (which only cares about the hidden types of things, not the opaque TAIT or RPIT type) and set it to run unconditionally (instead of depending on the optimization level and whether the inliner is active)

Author: bors

compiler/rustc_codegen_cranelift/src/base.rs

@@ -875,7 +875,7 @@ pub(crate) fn codegen_place<'tcx>(
             PlaceElem::Deref => {
                 cplace = cplace.place_deref(fx);
             }
-            PlaceElem::OpaqueCast(ty) => cplace = cplace.place_opaque_cast(fx, ty),
+            PlaceElem::OpaqueCast(ty) => bug!("encountered OpaqueCast({ty}) in codegen"),
             PlaceElem::Field(field, _ty) => {
                 cplace = cplace.place_field(fx, field);
             }

compiler/rustc_codegen_cranelift/src/value_and_place.rs

@@ -674,14 +674,6 @@ impl<'tcx> CPlace<'tcx> {
         }
     }
 
-    pub(crate) fn place_opaque_cast(
-        self,
-        fx: &mut FunctionCx<'_, '_, 'tcx>,
-        ty: Ty<'tcx>,
-    ) -> CPlace<'tcx> {
-        CPlace { inner: self.inner, layout: fx.layout_of(ty) }
-    }
-
     pub(crate) fn place_field(
         self,
         fx: &mut FunctionCx<'_, '_, 'tcx>,

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -463,7 +463,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 mir::ProjectionElem::Field(ref field, _) => {
                     cg_base.project_field(bx, field.index())
                 }
-                mir::ProjectionElem::OpaqueCast(ty) => cg_base.project_type(bx, ty),
+                mir::ProjectionElem::OpaqueCast(ty) => {
+                    bug!("encountered OpaqueCast({ty}) in codegen")
+                }
                 mir::ProjectionElem::Index(index) => {
                     let index = &mir::Operand::Copy(mir::Place::from(index));
                     let index = self.codegen_operand(bx, index);

compiler/rustc_const_eval/src/interpret/projection.rs

@@ -316,7 +316,9 @@ where
     {
         use rustc_middle::mir::ProjectionElem::*;
         Ok(match proj_elem {
-            OpaqueCast(ty) => base.transmute(self.layout_of(ty)?, self)?,
+            OpaqueCast(ty) => {
+                span_bug!(self.cur_span(), "OpaqueCast({ty}) encountered after borrowck")
+            }
             Field(field, _) => self.project_field(base, field.index())?,
             Downcast(_, variant) => self.project_downcast(base, variant)?,
             Deref => self.deref_pointer(&base.to_op(self)?)?.into(),

compiler/rustc_const_eval/src/transform/validate.rs

@@ -633,6 +633,14 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
         location: Location,
     ) {
         match elem {
+            ProjectionElem::OpaqueCast(ty)
+                if self.mir_phase >= MirPhase::Runtime(RuntimePhase::Initial) =>
+            {
+                self.fail(
+                    location,
+                    format!("explicit opaque type cast to `{ty}` after `RevealAll`"),
+                )
+            }
             ProjectionElem::Index(index) => {
                 let index_ty = self.body.local_decls[index].ty;
                 if index_ty != self.tcx.types.usize {

compiler/rustc_middle/src/mir/syntax.rs

@@ -139,6 +139,7 @@ pub enum RuntimePhase {
     /// * [`TerminatorKind::Yield`]
     /// * [`TerminatorKind::GeneratorDrop`]
     /// * [`Rvalue::Aggregate`] for any `AggregateKind` except `Array`
+    /// * [`PlaceElem::OpaqueCast`]
     ///
     /// And the following variants are allowed:
     /// * [`StatementKind::Retag`]

compiler/rustc_mir_dataflow/src/elaborate_drops.rs

@@ -194,6 +194,7 @@ where
     D: DropElaborator<'b, 'tcx>,
     'tcx: 'b,
 {
+    #[instrument(level = "trace", skip(self), ret)]
     fn place_ty(&self, place: Place<'tcx>) -> Ty<'tcx> {
         place.ty(self.elaborator.body(), self.tcx()).ty
     }
@@ -220,11 +221,9 @@ where
     //
     // FIXME: I think we should just control the flags externally,
     // and then we do not need this machinery.
+    #[instrument(level = "debug")]
     pub fn elaborate_drop(&mut self, bb: BasicBlock) {
-        debug!("elaborate_drop({:?}, {:?})", bb, self);
-        let style = self.elaborator.drop_style(self.path, DropFlagMode::Deep);
-        debug!("elaborate_drop({:?}, {:?}): live - {:?}", bb, self, style);
-        match style {
+        match self.elaborator.drop_style(self.path, DropFlagMode::Deep) {
             DropStyle::Dead => {
                 self.elaborator
                     .patch()

compiler/rustc_mir_transform/src/elaborate_drops.rs

@@ -170,6 +170,7 @@ impl<'a, 'tcx> DropElaborator<'a, 'tcx> for Elaborator<'a, '_, 'tcx> {
         self.ctxt.param_env()
     }
 
+    #[instrument(level = "debug", skip(self), ret)]
     fn drop_style(&self, path: Self::Path, mode: DropFlagMode) -> DropStyle {
         let ((maybe_live, maybe_dead), multipart) = match mode {
             DropFlagMode::Shallow => (self.ctxt.init_data.maybe_live_dead(path), false),

compiler/rustc_mir_transform/src/lib.rs

@@ -480,6 +480,7 @@ fn run_runtime_lowering_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let passes: &[&dyn MirPass<'tcx>] = &[
         // These next passes must be executed together
         &add_call_guards::CriticalCallEdges,
+        &reveal_all::RevealAll, // has to be done before drop elaboration, since we need to drop opaque types, too.
         &elaborate_drops::ElaborateDrops,
         // This will remove extraneous landing pads which are no longer
         // necessary as well as well as forcing any call in a non-unwinding
@@ -526,7 +527,6 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         body,
         &[
             &check_alignment::CheckAlignment,
-            &reveal_all::RevealAll, // has to be done before inlining, since inlined code is in RevealAll mode.
             &lower_slice_len::LowerSliceLenCalls, // has to be done before inlining, otherwise actual call will be almost always inlined. Also simple, so can just do first
             &unreachable_prop::UnreachablePropagation,
             &uninhabited_enum_branching::UninhabitedEnumBranching,

compiler/rustc_mir_transform/src/reveal_all.rs

@@ -8,16 +8,7 @@ use rustc_middle::ty::{self, Ty, TyCtxt};
 pub struct RevealAll;
 
 impl<'tcx> MirPass<'tcx> for RevealAll {
-    fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
-        sess.mir_opt_level() >= 3 || super::inline::Inline.is_enabled(sess)
-    }
-
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        // Do not apply this transformation to generators.
-        if body.generator.is_some() {
-            return;
-        }
-
         let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
         RevealAllVisitor { tcx, param_env }.visit_body_preserves_cfg(body);
     }
@@ -34,6 +25,29 @@ impl<'tcx> MutVisitor<'tcx> for RevealAllVisitor<'tcx> {
         self.tcx
     }
 
+    #[inline]
+    fn visit_place(
+        &mut self,
+        place: &mut Place<'tcx>,
+        _context: PlaceContext,
+        _location: Location,
+    ) {
+        // Performance optimization: don't reintern if there is no `OpaqueCast` to remove.
+        if place.projection.iter().all(|elem| !matches!(elem, ProjectionElem::OpaqueCast(_))) {
+            return;
+        }
+        // `OpaqueCast` projections are only needed if there are opaque types on which projections are performed.
+        // After the `RevealAll` pass, all opaque types are replaced with their hidden types, so we don't need these
+        // projections anymore.
+        place.projection = self.tcx.mk_place_elems(
+            &place
+                .projection
+                .into_iter()
+                .filter(|elem| !matches!(elem, ProjectionElem::OpaqueCast(_)))
+                .collect::<Vec<_>>(),
+        );
+    }
+
     #[inline]
     fn visit_constant(&mut self, constant: &mut ConstOperand<'tcx>, _: Location) {
         // We have to use `try_normalize_erasing_regions` here, since it's

tests/incremental/hashes/function_interfaces.rs

@@ -302,7 +302,7 @@ pub fn return_impl_trait() -> i32        {
 }
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg = "cfail2", except = "hir_owner, hir_owner_nodes, typeck, fn_sig, optimized_mir")]
+#[rustc_clean(cfg = "cfail2", except = "hir_owner, hir_owner_nodes, typeck, fn_sig")]
 #[rustc_clean(cfg = "cfail3")]
 #[rustc_clean(cfg = "cfail5", except = "hir_owner, hir_owner_nodes, typeck, fn_sig, optimized_mir")]
 #[rustc_clean(cfg = "cfail6")]

tests/mir-opt/building/async_await.b-{closure#0}.generator_resume.0.mir

@@ -2,13 +2,16 @@
 /* generator_layout = GeneratorLayout {
     field_tys: {
         _0: GeneratorSavedTy {
-            ty: Alias(
-                Opaque,
-                AliasTy {
-                    args: [
-                    ],
-                    def_id: DefId(0:7 ~ async_await[ccf8]::a::{opaque#0}),
-                },
+            ty: Generator(
+                DefId(0:4 ~ async_await[ccf8]::a::{closure#0}),
+                [
+                std::future::ResumeTy,
+                (),
+                (),
+                GeneratorWitness(DefId(0:4 ~ async_await[ccf8]::a::{closure#0}), []),
+                (),
+                ],
+                Static,
             ),
             source_info: SourceInfo {
                 span: $DIR/async_await.rs:15:9: 15:14 (#8),
@@ -17,13 +20,16 @@
             ignore_for_traits: false,
         },
         _1: GeneratorSavedTy {
-            ty: Alias(
-                Opaque,
-                AliasTy {
-                    args: [
-                    ],
-                    def_id: DefId(0:7 ~ async_await[ccf8]::a::{opaque#0}),
-                },
+            ty: Generator(
+                DefId(0:4 ~ async_await[ccf8]::a::{closure#0}),
+                [
+                std::future::ResumeTy,
+                (),
+                (),
+                GeneratorWitness(DefId(0:4 ~ async_await[ccf8]::a::{closure#0}), []),
+                (),
+                ],
+                Static,
             ),
             source_info: SourceInfo {
                 span: $DIR/async_await.rs:16:9: 16:14 (#10),
@@ -49,30 +55,30 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
     debug _task_context => _38;
     let mut _0: std::task::Poll<()>;
     let _3: ();
-    let mut _4: impl std::future::Future<Output = ()>;
-    let mut _5: impl std::future::Future<Output = ()>;
-    let mut _6: impl std::future::Future<Output = ()>;
+    let mut _4: {async fn body@$DIR/async_await.rs:11:14: 11:16};
+    let mut _5: {async fn body@$DIR/async_await.rs:11:14: 11:16};
+    let mut _6: {async fn body@$DIR/async_await.rs:11:14: 11:16};
     let mut _7: ();
     let _8: ();
     let mut _9: std::task::Poll<()>;
-    let mut _10: std::pin::Pin<&mut impl std::future::Future<Output = ()>>;
-    let mut _11: &mut impl std::future::Future<Output = ()>;
-    let mut _12: &mut impl std::future::Future<Output = ()>;
+    let mut _10: std::pin::Pin<&mut {async fn body@$DIR/async_await.rs:11:14: 11:16}>;
+    let mut _11: &mut {async fn body@$DIR/async_await.rs:11:14: 11:16};
+    let mut _12: &mut {async fn body@$DIR/async_await.rs:11:14: 11:16};
     let mut _13: &mut std::task::Context<'_>;
     let mut _14: &mut std::task::Context<'_>;
     let mut _15: &mut std::task::Context<'_>;
     let mut _16: isize;
     let mut _18: !;
     let mut _19: &mut std::task::Context<'_>;
     let mut _20: ();
-    let mut _21: impl std::future::Future<Output = ()>;
-    let mut _22: impl std::future::Future<Output = ()>;
-    let mut _23: impl std::future::Future<Output = ()>;
+    let mut _21: {async fn body@$DIR/async_await.rs:11:14: 11:16};
+    let mut _22: {async fn body@$DIR/async_await.rs:11:14: 11:16};
+    let mut _23: {async fn body@$DIR/async_await.rs:11:14: 11:16};
     let _24: ();
     let mut _25: std::task::Poll<()>;
-    let mut _26: std::pin::Pin<&mut impl std::future::Future<Output = ()>>;
-    let mut _27: &mut impl std::future::Future<Output = ()>;
-    let mut _28: &mut impl std::future::Future<Output = ()>;
+    let mut _26: std::pin::Pin<&mut {async fn body@$DIR/async_await.rs:11:14: 11:16}>;
+    let mut _27: &mut {async fn body@$DIR/async_await.rs:11:14: 11:16};
+    let mut _28: &mut {async fn body@$DIR/async_await.rs:11:14: 11:16};
     let mut _29: &mut std::task::Context<'_>;
     let mut _30: &mut std::task::Context<'_>;
     let mut _31: &mut std::task::Context<'_>;
@@ -84,7 +90,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
     let mut _38: &mut std::task::Context<'_>;
     let mut _39: u32;
     scope 1 {
-        debug __awaitee => (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#3).0: impl std::future::Future<Output = ()>);
+        debug __awaitee => (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#3).0: {async fn body@$DIR/async_await.rs:11:14: 11:16});
         let _17: ();
         scope 2 {
         }
@@ -93,7 +99,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
         }
     }
     scope 4 {
-        debug __awaitee => (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#4).0: impl std::future::Future<Output = ()>);
+        debug __awaitee => (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#4).0: {async fn body@$DIR/async_await.rs:11:14: 11:16});
         let _33: ();
         scope 5 {
         }
@@ -116,13 +122,13 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
     }
 
     bb2: {
-        _4 = <impl Future<Output = ()> as IntoFuture>::into_future(move _5) -> [return: bb3, unwind unreachable];
+        _4 = <{async fn body@$DIR/async_await.rs:11:14: 11:16} as IntoFuture>::into_future(move _5) -> [return: bb3, unwind unreachable];
     }
 
     bb3: {
         StorageDead(_5);
         nop;
-        (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#3).0: impl std::future::Future<Output = ()>) = move _4;
+        (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#3).0: {async fn body@$DIR/async_await.rs:11:14: 11:16}) = move _4;
         goto -> bb4;
     }
 
@@ -132,9 +138,9 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
         StorageLive(_10);
         StorageLive(_11);
         StorageLive(_12);
-        _12 = &mut (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#3).0: impl std::future::Future<Output = ()>);
+        _12 = &mut (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#3).0: {async fn body@$DIR/async_await.rs:11:14: 11:16});
         _11 = &mut (*_12);
-        _10 = Pin::<&mut impl Future<Output = ()>>::new_unchecked(move _11) -> [return: bb5, unwind unreachable];
+        _10 = Pin::<&mut {async fn body@$DIR/async_await.rs:11:14: 11:16}>::new_unchecked(move _11) -> [return: bb5, unwind unreachable];
     }
 
     bb5: {
@@ -150,7 +156,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
     bb6: {
         _13 = &mut (*_14);
         StorageDead(_15);
-        _9 = <impl Future<Output = ()> as Future>::poll(move _10, move _13) -> [return: bb7, unwind unreachable];
+        _9 = <{async fn body@$DIR/async_await.rs:11:14: 11:16} as Future>::poll(move _10, move _13) -> [return: bb7, unwind unreachable];
     }
 
     bb7: {
@@ -187,7 +193,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
         StorageDead(_12);
         StorageDead(_9);
         StorageDead(_8);
-        drop((((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#3).0: impl std::future::Future<Output = ()>)) -> [return: bb12, unwind unreachable];
+        drop((((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#3).0: {async fn body@$DIR/async_await.rs:11:14: 11:16})) -> [return: bb12, unwind unreachable];
     }
 
     bb11: {
@@ -212,13 +218,13 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
     }
 
     bb14: {
-        _21 = <impl Future<Output = ()> as IntoFuture>::into_future(move _22) -> [return: bb15, unwind unreachable];
+        _21 = <{async fn body@$DIR/async_await.rs:11:14: 11:16} as IntoFuture>::into_future(move _22) -> [return: bb15, unwind unreachable];
     }
 
     bb15: {
         StorageDead(_22);
         nop;
-        (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#4).0: impl std::future::Future<Output = ()>) = move _21;
+        (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#4).0: {async fn body@$DIR/async_await.rs:11:14: 11:16}) = move _21;
         goto -> bb16;
     }
 
@@ -228,9 +234,9 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
         StorageLive(_26);
         StorageLive(_27);
         StorageLive(_28);
-        _28 = &mut (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#4).0: impl std::future::Future<Output = ()>);
+        _28 = &mut (((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#4).0: {async fn body@$DIR/async_await.rs:11:14: 11:16});
         _27 = &mut (*_28);
-        _26 = Pin::<&mut impl Future<Output = ()>>::new_unchecked(move _27) -> [return: bb17, unwind unreachable];
+        _26 = Pin::<&mut {async fn body@$DIR/async_await.rs:11:14: 11:16}>::new_unchecked(move _27) -> [return: bb17, unwind unreachable];
     }
 
     bb17: {
@@ -246,7 +252,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
     bb18: {
         _29 = &mut (*_30);
         StorageDead(_31);
-        _25 = <impl Future<Output = ()> as Future>::poll(move _26, move _29) -> [return: bb19, unwind unreachable];
+        _25 = <{async fn body@$DIR/async_await.rs:11:14: 11:16} as Future>::poll(move _26, move _29) -> [return: bb19, unwind unreachable];
     }
 
     bb19: {
@@ -279,7 +285,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body@$DIR/async_await.rs:14:18: 17:2}>,
         StorageDead(_28);
         StorageDead(_25);
         StorageDead(_24);
-        drop((((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#4).0: impl std::future::Future<Output = ()>)) -> [return: bb23, unwind unreachable];
+        drop((((*(_1.0: &mut {async fn body@$DIR/async_await.rs:14:18: 17:2})) as variant#4).0: {async fn body@$DIR/async_await.rs:11:14: 11:16})) -> [return: bb23, unwind unreachable];
     }
 
     bb22: {