Rollup merge of rust-lang#132911 - compiler-errors:async-fn-sugar, r=fmease

Pretty print async fn sugar in opaques and trait bounds

sudo r? fmease

Author: compiler-errors

compiler/rustc_middle/src/middle/lang_items.rs

@@ -68,6 +68,17 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
+    /// Given a [`ty::ClosureKind`], get the [`DefId`] of its corresponding `Fn`-family
+    /// trait, if it is defined.
+    pub fn async_fn_trait_kind_to_def_id(self, kind: ty::ClosureKind) -> Option<DefId> {
+        let items = self.lang_items();
+        match kind {
+            ty::ClosureKind::Fn => items.async_fn_trait(),
+            ty::ClosureKind::FnMut => items.async_fn_mut_trait(),
+            ty::ClosureKind::FnOnce => items.async_fn_once_trait(),
+        }
+    }
+
     /// Returns `true` if `id` is a `DefId` of [`Fn`], [`FnMut`] or [`FnOnce`] traits.
     pub fn is_fn_trait(self, id: DefId) -> bool {
         self.fn_trait_kind_from_def_id(id).is_some()

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -16,8 +16,8 @@ use rustc_hir::definitions::{DefKey, DefPathDataName};
 use rustc_macros::{Lift, extension};
 use rustc_session::Limit;
 use rustc_session::cstore::{ExternCrate, ExternCrateSource};
-use rustc_span::FileNameDisplayPreference;
 use rustc_span::symbol::{Ident, Symbol, kw};
+use rustc_span::{FileNameDisplayPreference, sym};
 use rustc_type_ir::{Upcast as _, elaborate};
 use smallvec::SmallVec;
 
@@ -26,8 +26,8 @@ use super::*;
 use crate::mir::interpret::{AllocRange, GlobalAlloc, Pointer, Provenance, Scalar};
 use crate::query::{IntoQueryParam, Providers};
 use crate::ty::{
-    ConstInt, Expr, GenericArgKind, ParamConst, ScalarInt, Term, TermKind, TypeFoldable,
-    TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
+    ConstInt, Expr, GenericArgKind, ParamConst, ScalarInt, Term, TermKind, TraitPredicate,
+    TypeFoldable, TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
 };
 
 macro_rules! p {
@@ -993,10 +993,8 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
             match bound_predicate.skip_binder() {
                 ty::ClauseKind::Trait(pred) => {
-                    let trait_ref = bound_predicate.rebind(pred.trait_ref);
-
                     // Don't print `+ Sized`, but rather `+ ?Sized` if absent.
-                    if tcx.is_lang_item(trait_ref.def_id(), LangItem::Sized) {
+                    if tcx.is_lang_item(pred.def_id(), LangItem::Sized) {
                         match pred.polarity {
                             ty::PredicatePolarity::Positive => {
                                 has_sized_bound = true;
@@ -1007,24 +1005,22 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     }
 
                     self.insert_trait_and_projection(
-                        trait_ref,
-                        pred.polarity,
+                        bound_predicate.rebind(pred),
                         None,
                         &mut traits,
                         &mut fn_traits,
                     );
                 }
                 ty::ClauseKind::Projection(pred) => {
-                    let proj_ref = bound_predicate.rebind(pred);
-                    let trait_ref = proj_ref.required_poly_trait_ref(tcx);
-
-                    // Projection type entry -- the def-id for naming, and the ty.
-                    let proj_ty = (proj_ref.projection_def_id(), proj_ref.term());
+                    let proj = bound_predicate.rebind(pred);
+                    let trait_ref = proj.map_bound(|proj| TraitPredicate {
+                        trait_ref: proj.projection_term.trait_ref(tcx),
+                        polarity: ty::PredicatePolarity::Positive,
+                    });
 
                     self.insert_trait_and_projection(
                         trait_ref,
-                        ty::PredicatePolarity::Positive,
-                        Some(proj_ty),
+                        Some((proj.projection_def_id(), proj.term())),
                         &mut traits,
                         &mut fn_traits,
                     );
@@ -1042,88 +1038,66 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         // Insert parenthesis around (Fn(A, B) -> C) if the opaque ty has more than one other trait
         let paren_needed = fn_traits.len() > 1 || traits.len() > 0 || !has_sized_bound;
 
-        for (fn_once_trait_ref, entry) in fn_traits {
+        for ((bound_args, is_async), entry) in fn_traits {
             write!(self, "{}", if first { "" } else { " + " })?;
             write!(self, "{}", if paren_needed { "(" } else { "" })?;
 
-            self.wrap_binder(&fn_once_trait_ref, |trait_ref, cx| {
-                define_scoped_cx!(cx);
-                // Get the (single) generic ty (the args) of this FnOnce trait ref.
-                let generics = tcx.generics_of(trait_ref.def_id);
-                let own_args = generics.own_args_no_defaults(tcx, trait_ref.args);
-
-                match (entry.return_ty, own_args[0].expect_ty()) {
-                    // We can only print `impl Fn() -> ()` if we have a tuple of args and we recorded
-                    // a return type.
-                    (Some(return_ty), arg_tys) if matches!(arg_tys.kind(), ty::Tuple(_)) => {
-                        let name = if entry.fn_trait_ref.is_some() {
-                            "Fn"
-                        } else if entry.fn_mut_trait_ref.is_some() {
-                            "FnMut"
-                        } else {
-                            "FnOnce"
-                        };
-
-                        p!(write("{}(", name));
+            let trait_def_id = if is_async {
+                tcx.async_fn_trait_kind_to_def_id(entry.kind).expect("expected AsyncFn lang items")
+            } else {
+                tcx.fn_trait_kind_to_def_id(entry.kind).expect("expected Fn lang items")
+            };
 
-                        for (idx, ty) in arg_tys.tuple_fields().iter().enumerate() {
-                            if idx > 0 {
-                                p!(", ");
-                            }
-                            p!(print(ty));
-                        }
+            if let Some(return_ty) = entry.return_ty {
+                self.wrap_binder(&bound_args, |args, cx| {
+                    define_scoped_cx!(cx);
+                    p!(write("{}", tcx.item_name(trait_def_id)));
+                    p!("(");
 
-                        p!(")");
-                        if let Some(ty) = return_ty.skip_binder().as_type() {
-                            if !ty.is_unit() {
-                                p!(" -> ", print(return_ty));
-                            }
+                    for (idx, ty) in args.iter().enumerate() {
+                        if idx > 0 {
+                            p!(", ");
                         }
-                        p!(write("{}", if paren_needed { ")" } else { "" }));
-
-                        first = false;
+                        p!(print(ty));
                     }
-                    // If we got here, we can't print as a `impl Fn(A, B) -> C`. Just record the
-                    // trait_refs we collected in the OpaqueFnEntry as normal trait refs.
-                    _ => {
-                        if entry.has_fn_once {
-                            traits
-                                .entry((fn_once_trait_ref, ty::PredicatePolarity::Positive))
-                                .or_default()
-                                .extend(
-                                    // Group the return ty with its def id, if we had one.
-                                    entry.return_ty.map(|ty| {
-                                        (tcx.require_lang_item(LangItem::FnOnceOutput, None), ty)
-                                    }),
-                                );
-                        }
-                        if let Some(trait_ref) = entry.fn_mut_trait_ref {
-                            traits.entry((trait_ref, ty::PredicatePolarity::Positive)).or_default();
-                        }
-                        if let Some(trait_ref) = entry.fn_trait_ref {
-                            traits.entry((trait_ref, ty::PredicatePolarity::Positive)).or_default();
+
+                    p!(")");
+                    if let Some(ty) = return_ty.skip_binder().as_type() {
+                        if !ty.is_unit() {
+                            p!(" -> ", print(return_ty));
                         }
                     }
-                }
+                    p!(write("{}", if paren_needed { ")" } else { "" }));
 
-                Ok(())
-            })?;
+                    first = false;
+                    Ok(())
+                })?;
+            } else {
+                // Otherwise, render this like a regular trait.
+                traits.insert(
+                    bound_args.map_bound(|args| ty::TraitPredicate {
+                        polarity: ty::PredicatePolarity::Positive,
+                        trait_ref: ty::TraitRef::new(tcx, trait_def_id, [Ty::new_tup(tcx, args)]),
+                    }),
+                    FxIndexMap::default(),
+                );
+            }
         }
 
         // Print the rest of the trait types (that aren't Fn* family of traits)
-        for ((trait_ref, polarity), assoc_items) in traits {
+        for (trait_pred, assoc_items) in traits {
             write!(self, "{}", if first { "" } else { " + " })?;
 
-            self.wrap_binder(&trait_ref, |trait_ref, cx| {
+            self.wrap_binder(&trait_pred, |trait_pred, cx| {
                 define_scoped_cx!(cx);
 
-                if polarity == ty::PredicatePolarity::Negative {
+                if trait_pred.polarity == ty::PredicatePolarity::Negative {
                     p!("!");
                 }
-                p!(print(trait_ref.print_only_trait_name()));
+                p!(print(trait_pred.trait_ref.print_only_trait_name()));
 
-                let generics = tcx.generics_of(trait_ref.def_id);
-                let own_args = generics.own_args_no_defaults(tcx, trait_ref.args);
+                let generics = tcx.generics_of(trait_pred.def_id());
+                let own_args = generics.own_args_no_defaults(tcx, trait_pred.trait_ref.args);
 
                 if !own_args.is_empty() || !assoc_items.is_empty() {
                     let mut first = true;
@@ -1230,51 +1204,48 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
     /// traits map or fn_traits map, depending on if the trait is in the Fn* family of traits.
     fn insert_trait_and_projection(
         &mut self,
-        trait_ref: ty::PolyTraitRef<'tcx>,
-        polarity: ty::PredicatePolarity,
+        trait_pred: ty::PolyTraitPredicate<'tcx>,
         proj_ty: Option<(DefId, ty::Binder<'tcx, Term<'tcx>>)>,
         traits: &mut FxIndexMap<
-            (ty::PolyTraitRef<'tcx>, ty::PredicatePolarity),
+            ty::PolyTraitPredicate<'tcx>,
             FxIndexMap<DefId, ty::Binder<'tcx, Term<'tcx>>>,
         >,
-        fn_traits: &mut FxIndexMap<ty::PolyTraitRef<'tcx>, OpaqueFnEntry<'tcx>>,
+        fn_traits: &mut FxIndexMap<
+            (ty::Binder<'tcx, &'tcx ty::List<Ty<'tcx>>>, bool),
+            OpaqueFnEntry<'tcx>,
+        >,
     ) {
-        let trait_def_id = trait_ref.def_id();
-
-        // If our trait_ref is FnOnce or any of its children, project it onto the parent FnOnce
-        // super-trait ref and record it there.
-        // We skip negative Fn* bounds since they can't use parenthetical notation anyway.
-        if polarity == ty::PredicatePolarity::Positive
-            && let Some(fn_once_trait) = self.tcx().lang_items().fn_once_trait()
-        {
-            // If we have a FnOnce, then insert it into
-            if trait_def_id == fn_once_trait {
-                let entry = fn_traits.entry(trait_ref).or_default();
-                // Optionally insert the return_ty as well.
-                if let Some((_, ty)) = proj_ty {
-                    entry.return_ty = Some(ty);
-                }
-                entry.has_fn_once = true;
-                return;
-            } else if self.tcx().is_lang_item(trait_def_id, LangItem::FnMut) {
-                let super_trait_ref = elaborate::supertraits(self.tcx(), trait_ref)
-                    .find(|super_trait_ref| super_trait_ref.def_id() == fn_once_trait)
-                    .unwrap();
+        let tcx = self.tcx();
+        let trait_def_id = trait_pred.def_id();
 
-                fn_traits.entry(super_trait_ref).or_default().fn_mut_trait_ref = Some(trait_ref);
-                return;
-            } else if self.tcx().is_lang_item(trait_def_id, LangItem::Fn) {
-                let super_trait_ref = elaborate::supertraits(self.tcx(), trait_ref)
-                    .find(|super_trait_ref| super_trait_ref.def_id() == fn_once_trait)
-                    .unwrap();
+        let fn_trait_and_async = if let Some(kind) = tcx.fn_trait_kind_from_def_id(trait_def_id) {
+            Some((kind, false))
+        } else if let Some(kind) = tcx.async_fn_trait_kind_from_def_id(trait_def_id) {
+            Some((kind, true))
+        } else {
+            None
+        };
 
-                fn_traits.entry(super_trait_ref).or_default().fn_trait_ref = Some(trait_ref);
-                return;
+        if trait_pred.polarity() == ty::PredicatePolarity::Positive
+            && let Some((kind, is_async)) = fn_trait_and_async
+            && let ty::Tuple(types) = *trait_pred.skip_binder().trait_ref.args.type_at(1).kind()
+        {
+            let entry = fn_traits
+                .entry((trait_pred.rebind(types), is_async))
+                .or_insert_with(|| OpaqueFnEntry { kind, return_ty: None });
+            if kind.extends(entry.kind) {
+                entry.kind = kind;
+            }
+            if let Some((proj_def_id, proj_ty)) = proj_ty
+                && tcx.item_name(proj_def_id) == sym::Output
+            {
+                entry.return_ty = Some(proj_ty);
             }
+            return;
         }
 
         // Otherwise, just group our traits and projection types.
-        traits.entry((trait_ref, polarity)).or_default().extend(proj_ty);
+        traits.entry(trait_pred).or_default().extend(proj_ty);
     }
 
     fn pretty_print_inherent_projection(
@@ -3189,10 +3160,10 @@ define_print_and_forward_display! {
 
     TraitRefPrintSugared<'tcx> {
         if !with_reduced_queries()
-            && let Some(kind) = cx.tcx().fn_trait_kind_from_def_id(self.0.def_id)
+            && cx.tcx().trait_def(self.0.def_id).paren_sugar
             && let ty::Tuple(args) = self.0.args.type_at(1).kind()
         {
-            p!(write("{}", kind.as_str()), "(");
+            p!(write("{}", cx.tcx().item_name(self.0.def_id)), "(");
             for (i, arg) in args.iter().enumerate() {
                 if i > 0 {
                     p!(", ");
@@ -3415,11 +3386,7 @@ pub fn provide(providers: &mut Providers) {
     *providers = Providers { trimmed_def_paths, ..*providers };
 }
 
-#[derive(Default)]
 pub struct OpaqueFnEntry<'tcx> {
-    // The trait ref is already stored as a key, so just track if we have it as a real predicate
-    has_fn_once: bool,
-    fn_mut_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
-    fn_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
+    kind: ty::ClosureKind,
     return_ty: Option<ty::Binder<'tcx, Term<'tcx>>>,
 }

compiler/rustc_type_ir/src/predicate.rs

@@ -684,19 +684,6 @@ impl<I: Interner> ty::Binder<I, ProjectionPredicate<I>> {
         self.skip_binder().projection_term.trait_def_id(cx)
     }
 
-    /// Get the trait ref required for this projection to be well formed.
-    /// Note that for generic associated types the predicates of the associated
-    /// type also need to be checked.
-    #[inline]
-    pub fn required_poly_trait_ref(&self, cx: I) -> ty::Binder<I, TraitRef<I>> {
-        // Note: unlike with `TraitRef::to_poly_trait_ref()`,
-        // `self.0.trait_ref` is permitted to have escaping regions.
-        // This is because here `self` has a `Binder` and so does our
-        // return value, so we are preserving the number of binding
-        // levels.
-        self.map_bound(|predicate| predicate.projection_term.trait_ref(cx))
-    }
-
     pub fn term(&self) -> ty::Binder<I, I::Term> {
         self.map_bound(|predicate| predicate.term)
     }

tests/ui/async-await/async-closures/fn-exception-target-features.stderr

@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {target_feature}: AsyncFn<()>` is not satisfied
+error[E0277]: the trait bound `fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {target_feature}: AsyncFn()` is not satisfied
   --> $DIR/fn-exception-target-features.rs:16:10
    |
 LL |     test(target_feature);
-   |     ---- ^^^^^^^^^^^^^^ the trait `AsyncFn<()>` is not implemented for fn item `fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {target_feature}`
+   |     ---- ^^^^^^^^^^^^^^ the trait `AsyncFn()` is not implemented for fn item `fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {target_feature}`
    |     |
    |     required by a bound introduced by this call
    |

tests/ui/async-await/async-closures/fn-exception.stderr

@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `unsafe fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {unsafety}: AsyncFn<()>` is not satisfied
+error[E0277]: the trait bound `unsafe fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {unsafety}: AsyncFn()` is not satisfied
   --> $DIR/fn-exception.rs:19:10
    |
 LL |     test(unsafety);
-   |     ---- ^^^^^^^^ the trait `AsyncFn<()>` is not implemented for fn item `unsafe fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {unsafety}`
+   |     ---- ^^^^^^^^ the trait `AsyncFn()` is not implemented for fn item `unsafe fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {unsafety}`
    |     |
    |     required by a bound introduced by this call
    |
@@ -12,11 +12,11 @@ note: required by a bound in `test`
 LL | fn test(f: impl async Fn()) {}
    |                 ^^^^^^^^^^ required by this bound in `test`
 
-error[E0277]: the trait bound `extern "C" fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {abi}: AsyncFn<()>` is not satisfied
+error[E0277]: the trait bound `extern "C" fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {abi}: AsyncFn()` is not satisfied
   --> $DIR/fn-exception.rs:20:10
    |
 LL |     test(abi);
-   |     ---- ^^^ the trait `AsyncFn<()>` is not implemented for fn item `extern "C" fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {abi}`
+   |     ---- ^^^ the trait `AsyncFn()` is not implemented for fn item `extern "C" fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {abi}`
    |     |
    |     required by a bound introduced by this call
    |

tests/ui/async-await/async-closures/pretty-async-fn-opaque.rs

@@ -0,0 +1,14 @@
+//@ edition: 2021
+
+#![feature(async_closure)]
+
+use std::ops::AsyncFnMut;
+
+fn produce() -> impl AsyncFnMut() -> &'static str {
+    async || ""
+}
+
+fn main() {
+    let x: i32 = produce();
+    //~^ ERROR mismatched types
+}