Auto merge of #115759 - oli-obk:open_drop_from_non-ADT, r=<try>

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)

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

@@ -8,10 +8,6 @@ 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() {

tests/ui/polymorphization/generators.rs

@@ -32,6 +32,7 @@ where
 
 #[rustc_polymorphize_error]
 pub fn unused_type<T>() -> impl Generator<(), Yield = u32, Return = u32> + Unpin {
+    //~^ ERROR item has unused generic parameters
     || {
         //~^ ERROR item has unused generic parameters
         yield 1;
@@ -57,6 +58,7 @@ pub fn used_type_in_return<R: Default>() -> impl Generator<(), Yield = u32, Retu
 
 #[rustc_polymorphize_error]
 pub fn unused_const<const T: u32>() -> impl Generator<(), Yield = u32, Return = u32> + Unpin {
+    //~^ ERROR item has unused generic parameters
     || {
         //~^ ERROR item has unused generic parameters
         yield 1;

tests/ui/polymorphization/generators.stderr

@@ -8,20 +8,34 @@ LL | #![feature(generic_const_exprs, generators, generator_trait, rustc_attrs)]
    = note: `#[warn(incomplete_features)]` on by default
 
 error: item has unused generic parameters
-  --> $DIR/generators.rs:35:5
+  --> $DIR/generators.rs:36:5
    |
 LL | pub fn unused_type<T>() -> impl Generator<(), Yield = u32, Return = u32> + Unpin {
    |                    - generic parameter `T` is unused
+LL |
 LL |     || {
    |     ^^
 
 error: item has unused generic parameters
-  --> $DIR/generators.rs:60:5
+  --> $DIR/generators.rs:34:8
+   |
+LL | pub fn unused_type<T>() -> impl Generator<(), Yield = u32, Return = u32> + Unpin {
+   |        ^^^^^^^^^^^ - generic parameter `T` is unused
+
+error: item has unused generic parameters
+  --> $DIR/generators.rs:62:5
    |
 LL | pub fn unused_const<const T: u32>() -> impl Generator<(), Yield = u32, Return = u32> + Unpin {
    |                     ------------ generic parameter `T` is unused
+LL |
 LL |     || {
    |     ^^
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: item has unused generic parameters
+  --> $DIR/generators.rs:60:8
+   |
+LL | pub fn unused_const<const T: u32>() -> impl Generator<(), Yield = u32, Return = u32> + Unpin {
+   |        ^^^^^^^^^^^^ ------------ generic parameter `T` is unused
+
+error: aborting due to 4 previous errors; 1 warning emitted
 

tests/ui/type-alias-impl-trait/destructure_tait-ice-113594.rs

@@ -0,0 +1,18 @@
+// build-pass
+
+#![feature(type_alias_impl_trait)]
+
+pub struct Foo {
+    /// This type must have nontrivial drop glue
+    field: String,
+}
+
+pub type Tait = impl Sized;
+
+pub fn ice_cold(beverage: Tait) {
+    // Must destructure at least one field of `Foo`
+    let Foo { field } = beverage;
+    _ = field;
+}
+
+fn main() {}