Auto merge of rust-lang#118684 - compiler-errors:yeet-poly-gen-sig, r=spastorino

Remove `PolyGenSig` since it's always a dummy binder

Coroutines are never polymorphic in their signature. This cleans up a FIXME in the code:

```
    /// Returns the "coroutine signature", which consists of its yield
    /// and return types.
    ///
    /// N.B., some bits of the code prefers to see this wrapped in a
    /// binder, but it never contains bound regions. Probably this
    /// function should be removed.
```

Author: bors

compiler/rustc_middle/src/ty/mod.rs

@@ -98,9 +98,8 @@ pub use self::sty::{
     CoroutineArgs, CoroutineArgsParts, EarlyParamRegion, ExistentialPredicate,
     ExistentialProjection, ExistentialTraitRef, FnSig, GenSig, InlineConstArgs,
     InlineConstArgsParts, LateParamRegion, ParamConst, ParamTy, PolyExistentialPredicate,
-    PolyExistentialProjection, PolyExistentialTraitRef, PolyFnSig, PolyGenSig, PolyTraitRef,
-    PredicateKind, Region, RegionKind, RegionVid, TraitRef, TyKind, TypeAndMut, UpvarArgs,
-    VarianceDiagInfo,
+    PolyExistentialProjection, PolyExistentialTraitRef, PolyFnSig, PolyTraitRef, PredicateKind,
+    Region, RegionKind, RegionVid, TraitRef, TyKind, TypeAndMut, UpvarArgs, VarianceDiagInfo,
 };
 pub use self::trait_def::TraitDef;
 pub use self::typeck_results::{

compiler/rustc_middle/src/ty/sty.rs

@@ -468,16 +468,6 @@ impl<'tcx> CoroutineArgs<'tcx> {
         self.split().return_ty.expect_ty()
     }
 
-    /// Returns the "coroutine signature", which consists of its yield
-    /// and return types.
-    ///
-    /// N.B., some bits of the code prefers to see this wrapped in a
-    /// binder, but it never contains bound regions. Probably this
-    /// function should be removed.
-    pub fn poly_sig(self) -> PolyGenSig<'tcx> {
-        ty::Binder::dummy(self.sig())
-    }
-
     /// Returns the "coroutine signature", which consists of its resume, yield
     /// and return types.
     pub fn sig(self) -> GenSig<'tcx> {
@@ -1352,8 +1342,6 @@ pub struct GenSig<'tcx> {
     pub return_ty: Ty<'tcx>,
 }
 
-pub type PolyGenSig<'tcx> = Binder<'tcx, GenSig<'tcx>>;
-
 /// Signature of a function type, which we have arbitrarily
 /// decided to use to refer to the input/output types.
 ///

compiler/rustc_trait_selection/src/traits/project.rs

@@ -2076,7 +2076,7 @@ fn confirm_coroutine_candidate<'cx, 'tcx>(
     else {
         unreachable!()
     };
-    let coroutine_sig = args.as_coroutine().poly_sig();
+    let coroutine_sig = args.as_coroutine().sig();
     let Normalized { value: coroutine_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2091,29 +2091,28 @@ fn confirm_coroutine_candidate<'cx, 'tcx>(
 
     let coroutine_def_id = tcx.require_lang_item(LangItem::Coroutine, None);
 
-    let predicate = super::util::coroutine_trait_ref_and_outputs(
+    let (trait_ref, yield_ty, return_ty) = super::util::coroutine_trait_ref_and_outputs(
         tcx,
         coroutine_def_id,
         obligation.predicate.self_ty(),
         coroutine_sig,
-    )
-    .map_bound(|(trait_ref, yield_ty, return_ty)| {
-        let name = tcx.associated_item(obligation.predicate.def_id).name;
-        let ty = if name == sym::Return {
-            return_ty
-        } else if name == sym::Yield {
-            yield_ty
-        } else {
-            bug!()
-        };
+    );
 
-        ty::ProjectionPredicate {
-            projection_ty: ty::AliasTy::new(tcx, obligation.predicate.def_id, trait_ref.args),
-            term: ty.into(),
-        }
-    });
+    let name = tcx.associated_item(obligation.predicate.def_id).name;
+    let ty = if name == sym::Return {
+        return_ty
+    } else if name == sym::Yield {
+        yield_ty
+    } else {
+        bug!()
+    };
+
+    let predicate = ty::ProjectionPredicate {
+        projection_ty: ty::AliasTy::new(tcx, obligation.predicate.def_id, trait_ref.args),
+        term: ty.into(),
+    };
 
-    confirm_param_env_candidate(selcx, obligation, predicate, false)
+    confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false)
         .with_addl_obligations(nested)
         .with_addl_obligations(obligations)
 }
@@ -2128,7 +2127,7 @@ fn confirm_future_candidate<'cx, 'tcx>(
     else {
         unreachable!()
     };
-    let coroutine_sig = args.as_coroutine().poly_sig();
+    let coroutine_sig = args.as_coroutine().sig();
     let Normalized { value: coroutine_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2142,22 +2141,21 @@ fn confirm_future_candidate<'cx, 'tcx>(
     let tcx = selcx.tcx();
     let fut_def_id = tcx.require_lang_item(LangItem::Future, None);
 
-    let predicate = super::util::future_trait_ref_and_outputs(
+    let (trait_ref, return_ty) = super::util::future_trait_ref_and_outputs(
         tcx,
         fut_def_id,
         obligation.predicate.self_ty(),
         coroutine_sig,
-    )
-    .map_bound(|(trait_ref, return_ty)| {
-        debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Output);
+    );
 
-        ty::ProjectionPredicate {
-            projection_ty: ty::AliasTy::new(tcx, obligation.predicate.def_id, trait_ref.args),
-            term: return_ty.into(),
-        }
-    });
+    debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Output);
+
+    let predicate = ty::ProjectionPredicate {
+        projection_ty: ty::AliasTy::new(tcx, obligation.predicate.def_id, trait_ref.args),
+        term: return_ty.into(),
+    };
 
-    confirm_param_env_candidate(selcx, obligation, predicate, false)
+    confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false)
         .with_addl_obligations(nested)
         .with_addl_obligations(obligations)
 }
@@ -2172,7 +2170,7 @@ fn confirm_iterator_candidate<'cx, 'tcx>(
     else {
         unreachable!()
     };
-    let gen_sig = args.as_coroutine().poly_sig();
+    let gen_sig = args.as_coroutine().sig();
     let Normalized { value: gen_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2186,22 +2184,21 @@ fn confirm_iterator_candidate<'cx, 'tcx>(
     let tcx = selcx.tcx();
     let iter_def_id = tcx.require_lang_item(LangItem::Iterator, None);
 
-    let predicate = super::util::iterator_trait_ref_and_outputs(
+    let (trait_ref, yield_ty) = super::util::iterator_trait_ref_and_outputs(
         tcx,
         iter_def_id,
         obligation.predicate.self_ty(),
         gen_sig,
-    )
-    .map_bound(|(trait_ref, yield_ty)| {
-        debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Item);
+    );
 
-        ty::ProjectionPredicate {
-            projection_ty: ty::AliasTy::new(tcx, obligation.predicate.def_id, trait_ref.args),
-            term: yield_ty.into(),
-        }
-    });
+    debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Item);
 
-    confirm_param_env_candidate(selcx, obligation, predicate, false)
+    let predicate = ty::ProjectionPredicate {
+        projection_ty: ty::AliasTy::new(tcx, obligation.predicate.def_id, trait_ref.args),
+        term: yield_ty.into(),
+    };
+
+    confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false)
         .with_addl_obligations(nested)
         .with_addl_obligations(obligations)
 }

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -731,7 +731,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         debug!(?obligation, ?coroutine_def_id, ?args, "confirm_coroutine_candidate");
 
-        let coroutine_sig = args.as_coroutine().poly_sig();
+        let coroutine_sig = args.as_coroutine().sig();
 
         // NOTE: The self-type is a coroutine type and hence is
         // in fact unparameterized (or at least does not reference any
@@ -742,15 +742,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .no_bound_vars()
             .expect("unboxed closure type should not capture bound vars from the predicate");
 
-        let trait_ref = super::util::coroutine_trait_ref_and_outputs(
+        let (trait_ref, _, _) = super::util::coroutine_trait_ref_and_outputs(
             self.tcx(),
             obligation.predicate.def_id(),
             self_ty,
             coroutine_sig,
-        )
-        .map_bound(|(trait_ref, ..)| trait_ref);
+        );
 
-        let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
+        let nested = self.confirm_poly_trait_refs(obligation, ty::Binder::dummy(trait_ref))?;
         debug!(?trait_ref, ?nested, "coroutine candidate obligations");
 
         Ok(nested)
@@ -770,17 +769,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         debug!(?obligation, ?coroutine_def_id, ?args, "confirm_future_candidate");
 
-        let coroutine_sig = args.as_coroutine().poly_sig();
+        let coroutine_sig = args.as_coroutine().sig();
 
-        let trait_ref = super::util::future_trait_ref_and_outputs(
+        let (trait_ref, _) = super::util::future_trait_ref_and_outputs(
             self.tcx(),
             obligation.predicate.def_id(),
             obligation.predicate.no_bound_vars().expect("future has no bound vars").self_ty(),
             coroutine_sig,
-        )
-        .map_bound(|(trait_ref, ..)| trait_ref);
+        );
 
-        let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
+        let nested = self.confirm_poly_trait_refs(obligation, ty::Binder::dummy(trait_ref))?;
         debug!(?trait_ref, ?nested, "future candidate obligations");
 
         Ok(nested)
@@ -800,17 +798,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         debug!(?obligation, ?coroutine_def_id, ?args, "confirm_iterator_candidate");
 
-        let gen_sig = args.as_coroutine().poly_sig();
+        let gen_sig = args.as_coroutine().sig();
 
-        let trait_ref = super::util::iterator_trait_ref_and_outputs(
+        let (trait_ref, _) = super::util::iterator_trait_ref_and_outputs(
             self.tcx(),
             obligation.predicate.def_id(),
             obligation.predicate.no_bound_vars().expect("iterator has no bound vars").self_ty(),
             gen_sig,
-        )
-        .map_bound(|(trait_ref, ..)| trait_ref);
+        );
 
-        let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
+        let nested = self.confirm_poly_trait_refs(obligation, ty::Binder::dummy(trait_ref))?;
         debug!(?trait_ref, ?nested, "iterator candidate obligations");
 
         Ok(nested)

compiler/rustc_trait_selection/src/traits/util.rs

@@ -279,33 +279,33 @@ pub fn coroutine_trait_ref_and_outputs<'tcx>(
     tcx: TyCtxt<'tcx>,
     fn_trait_def_id: DefId,
     self_ty: Ty<'tcx>,
-    sig: ty::PolyGenSig<'tcx>,
-) -> ty::Binder<'tcx, (ty::TraitRef<'tcx>, Ty<'tcx>, Ty<'tcx>)> {
+    sig: ty::GenSig<'tcx>,
+) -> (ty::TraitRef<'tcx>, Ty<'tcx>, Ty<'tcx>) {
     assert!(!self_ty.has_escaping_bound_vars());
-    let trait_ref = ty::TraitRef::new(tcx, fn_trait_def_id, [self_ty, sig.skip_binder().resume_ty]);
-    sig.map_bound(|sig| (trait_ref, sig.yield_ty, sig.return_ty))
+    let trait_ref = ty::TraitRef::new(tcx, fn_trait_def_id, [self_ty, sig.resume_ty]);
+    (trait_ref, sig.yield_ty, sig.return_ty)
 }
 
 pub fn future_trait_ref_and_outputs<'tcx>(
     tcx: TyCtxt<'tcx>,
     fn_trait_def_id: DefId,
     self_ty: Ty<'tcx>,
-    sig: ty::PolyGenSig<'tcx>,
-) -> ty::Binder<'tcx, (ty::TraitRef<'tcx>, Ty<'tcx>)> {
+    sig: ty::GenSig<'tcx>,
+) -> (ty::TraitRef<'tcx>, Ty<'tcx>) {
     assert!(!self_ty.has_escaping_bound_vars());
     let trait_ref = ty::TraitRef::new(tcx, fn_trait_def_id, [self_ty]);
-    sig.map_bound(|sig| (trait_ref, sig.return_ty))
+    (trait_ref, sig.return_ty)
 }
 
 pub fn iterator_trait_ref_and_outputs<'tcx>(
     tcx: TyCtxt<'tcx>,
     iterator_def_id: DefId,
     self_ty: Ty<'tcx>,
-    sig: ty::PolyGenSig<'tcx>,
-) -> ty::Binder<'tcx, (ty::TraitRef<'tcx>, Ty<'tcx>)> {
+    sig: ty::GenSig<'tcx>,
+) -> (ty::TraitRef<'tcx>, Ty<'tcx>) {
     assert!(!self_ty.has_escaping_bound_vars());
     let trait_ref = ty::TraitRef::new(tcx, iterator_def_id, [self_ty]);
-    sig.map_bound(|sig| (trait_ref, sig.yield_ty))
+    (trait_ref, sig.yield_ty)
 }
 
 pub fn impl_item_is_final(tcx: TyCtxt<'_>, assoc_item: &ty::AssocItem) -> bool {

compiler/rustc_ty_utils/src/abi.rs

@@ -99,11 +99,11 @@ fn fn_sig_for_fn_abi<'tcx>(
         }
         ty::Coroutine(did, args, _) => {
             let coroutine_kind = tcx.coroutine_kind(did).unwrap();
-            let sig = args.as_coroutine().poly_sig();
+            let sig = args.as_coroutine().sig();
 
-            let bound_vars = tcx.mk_bound_variable_kinds_from_iter(
-                sig.bound_vars().iter().chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
-            );
+            let bound_vars = tcx.mk_bound_variable_kinds_from_iter(iter::once(
+                ty::BoundVariableKind::Region(ty::BrEnv),
+            ));
             let br = ty::BoundRegion {
                 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
                 kind: ty::BoundRegionKind::BrEnv,
@@ -124,7 +124,6 @@ fn fn_sig_for_fn_abi<'tcx>(
                 }
             };
 
-            let sig = sig.skip_binder();
             // The `FnSig` and the `ret_ty` here is for a coroutines main
             // `Coroutine::resume(...) -> CoroutineState` function in case we
             // have an ordinary coroutine, the `Future::poll(...) -> Poll`