From 0eb2adb7e877ceaa7d4919f7b881508ee507ec3b Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 26 Jan 2024 17:00:28 +0000
Subject: [PATCH 1/4] Add async bound modifier to enable async Fn bounds
---
compiler/rustc_ast/src/ast.rs | 29 ++++++-
compiler/rustc_ast_lowering/src/expr.rs | 2 +
compiler/rustc_ast_lowering/src/item.rs | 13 ++-
compiler/rustc_ast_lowering/src/lib.rs | 19 ++--
compiler/rustc_ast_lowering/src/path.rs | 87 +++++++++++++++++--
compiler/rustc_ast_pretty/src/pprust/state.rs | 21 +++--
compiler/rustc_expand/src/build.rs | 1 +
compiler/rustc_parse/src/parser/ty.rs | 16 ++--
compiler/rustc_span/src/hygiene.rs | 3 +
compiler/rustc_span/src/symbol.rs | 1 +
tests/ui/async-await/async-fn/sugar.rs | 14 +++
tests/ui/stats/hir-stats.stderr | 52 +++++------
12 files changed, 199 insertions(+), 59 deletions(-)
create mode 100644 tests/ui/async-await/async-fn/sugar.rs
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 4eb8169d0c3..296a570de6b 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -291,12 +291,16 @@ pub use crate::node_id::{NodeId, CRATE_NODE_ID, DUMMY_NODE_ID};
#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug)]
pub struct TraitBoundModifiers {
pub constness: BoundConstness,
+ pub asyncness: BoundAsyncness,
pub polarity: BoundPolarity,
}
impl TraitBoundModifiers {
- pub const NONE: Self =
- Self { constness: BoundConstness::Never, polarity: BoundPolarity::Positive };
+ pub const NONE: Self = Self {
+ constness: BoundConstness::Never,
+ asyncness: BoundAsyncness::Normal,
+ polarity: BoundPolarity::Positive,
+ };
}
/// The AST represents all type param bounds as types.
@@ -2562,6 +2566,25 @@ impl BoundConstness {
}
}
+/// The asyncness of a trait bound.
+#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug)]
+#[derive(HashStable_Generic)]
+pub enum BoundAsyncness {
+ /// `Type: Trait`
+ Normal,
+ /// `Type: async Trait`
+ Async(Span),
+}
+
+impl BoundAsyncness {
+ pub fn as_str(self) -> &'static str {
+ match self {
+ Self::Normal => "",
+ Self::Async(_) => "async",
+ }
+ }
+}
+
#[derive(Clone, Encodable, Decodable, Debug)]
pub enum FnRetTy {
/// Returns type is not specified.
@@ -3300,7 +3323,7 @@ mod size_asserts {
static_assert_size!(ForeignItem, 96);
static_assert_size!(ForeignItemKind, 24);
static_assert_size!(GenericArg, 24);
- static_assert_size!(GenericBound, 72);
+ static_assert_size!(GenericBound, 88);
static_assert_size!(Generics, 40);
static_assert_size!(Impl, 136);
static_assert_size!(Item, 136);
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 0ad4a59c17e..3b00a84e67e 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -100,6 +100,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
ParenthesizedGenericArgs::Err,
&ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
+ // Method calls can't have bound modifiers
+ None,
));
let receiver = self.lower_expr(receiver);
let args =
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index dd3f7289a60..0ff5d96cec2 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -343,14 +343,19 @@ impl<'hir> LoweringContext<'_, 'hir> {
let itctx = ImplTraitContext::Universal;
let (generics, (trait_ref, lowered_ty)) =
self.lower_generics(ast_generics, *constness, id, &itctx, |this| {
- let constness = match *constness {
- Const::Yes(span) => BoundConstness::Maybe(span),
- Const::No => BoundConstness::Never,
+ let modifiers = TraitBoundModifiers {
+ constness: match *constness {
+ Const::Yes(span) => BoundConstness::Maybe(span),
+ Const::No => BoundConstness::Never,
+ },
+ asyncness: BoundAsyncness::Normal,
+ // we don't use this in bound lowering
+ polarity: BoundPolarity::Positive,
};
let trait_ref = trait_ref.as_ref().map(|trait_ref| {
this.lower_trait_ref(
- constness,
+ modifiers,
trait_ref,
&ImplTraitContext::Disallowed(ImplTraitPosition::Trait),
)
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 3621844efc8..7dfef9c07c5 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -131,6 +131,7 @@ struct LoweringContext<'a, 'hir> {
allow_gen_future: Lrc<[Symbol]>,
allow_async_iterator: Lrc<[Symbol]>,
allow_for_await: Lrc<[Symbol]>,
+ allow_async_fn_traits: Lrc<[Symbol]>,
/// Mapping from generics `def_id`s to TAIT generics `def_id`s.
/// For each captured lifetime (e.g., 'a), we create a new lifetime parameter that is a generic
@@ -176,6 +177,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
[sym::gen_future].into()
},
allow_for_await: [sym::async_iterator].into(),
+ allow_async_fn_traits: [sym::async_fn_traits].into(),
// FIXME(gen_blocks): how does `closure_track_caller`/`async_fn_track_caller`
// interact with `gen`/`async gen` blocks
allow_async_iterator: [sym::gen_future, sym::async_iterator].into(),
@@ -1311,7 +1313,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
span: t.span,
},
itctx,
- ast::BoundConstness::Never,
+ TraitBoundModifiers::NONE,
);
let bounds = this.arena.alloc_from_iter([bound]);
let lifetime_bound = this.elided_dyn_bound(t.span);
@@ -1426,7 +1428,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
itctx,
// Still, don't pass along the constness here; we don't want to
// synthesize any host effect args, it'd only cause problems.
- ast::BoundConstness::Never,
+ TraitBoundModifiers {
+ constness: BoundConstness::Never,
+ ..*modifiers
+ },
))
}
BoundPolarity::Maybe(_) => None,
@@ -2019,7 +2024,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
) -> hir::GenericBound<'hir> {
match tpb {
GenericBound::Trait(p, modifiers) => hir::GenericBound::Trait(
- self.lower_poly_trait_ref(p, itctx, modifiers.constness.into()),
+ self.lower_poly_trait_ref(p, itctx, *modifiers),
self.lower_trait_bound_modifiers(*modifiers),
),
GenericBound::Outlives(lifetime) => {
@@ -2192,7 +2197,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
fn lower_trait_ref(
&mut self,
- constness: ast::BoundConstness,
+ modifiers: ast::TraitBoundModifiers,
p: &TraitRef,
itctx: &ImplTraitContext,
) -> hir::TraitRef<'hir> {
@@ -2202,7 +2207,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
&p.path,
ParamMode::Explicit,
itctx,
- Some(constness),
+ Some(modifiers),
) {
hir::QPath::Resolved(None, path) => path,
qpath => panic!("lower_trait_ref: unexpected QPath `{qpath:?}`"),
@@ -2215,11 +2220,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
&mut self,
p: &PolyTraitRef,
itctx: &ImplTraitContext,
- constness: ast::BoundConstness,
+ modifiers: ast::TraitBoundModifiers,
) -> hir::PolyTraitRef<'hir> {
let bound_generic_params =
self.lower_lifetime_binder(p.trait_ref.ref_id, &p.bound_generic_params);
- let trait_ref = self.lower_trait_ref(constness, &p.trait_ref, itctx);
+ let trait_ref = self.lower_trait_ref(modifiers, &p.trait_ref, itctx);
hir::PolyTraitRef { bound_generic_params, trait_ref, span: self.lower_span(p.span) }
}
diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index c679ee56fcd..b4f1d7ce8c2 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -6,12 +6,14 @@ use super::{GenericArgsCtor, LifetimeRes, ParenthesizedGenericArgs};
use super::{ImplTraitContext, LoweringContext, ParamMode};
use rustc_ast::{self as ast, *};
+use rustc_data_structures::sync::Lrc;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, PartialRes, Res};
+use rustc_hir::def_id::DefId;
use rustc_hir::GenericArg;
use rustc_middle::span_bug;
use rustc_span::symbol::{kw, sym, Ident};
-use rustc_span::{BytePos, Span, DUMMY_SP};
+use rustc_span::{BytePos, DesugaringKind, Span, Symbol, DUMMY_SP};
use smallvec::{smallvec, SmallVec};
@@ -24,8 +26,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
p: &Path,
param_mode: ParamMode,
itctx: &ImplTraitContext,
- // constness of the impl/bound if this is a trait path
- constness: Option<ast::BoundConstness>,
+ // modifiers of the impl/bound if this is a trait path
+ modifiers: Option<ast::TraitBoundModifiers>,
) -> hir::QPath<'hir> {
let qself_position = qself.as_ref().map(|q| q.position);
let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx));
@@ -35,10 +37,27 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let base_res = partial_res.base_res();
let unresolved_segments = partial_res.unresolved_segments();
+ let mut res = self.lower_res(base_res);
+
+ // When we have an `async` kw on a bound, map the trait it resolves to.
+ let mut bound_modifier_allowed_features = None;
+ if let Some(TraitBoundModifiers { asyncness: BoundAsyncness::Async(_), .. }) = modifiers {
+ if let Res::Def(DefKind::Trait, def_id) = res {
+ if let Some((async_def_id, features)) = self.map_trait_to_async_trait(def_id) {
+ res = Res::Def(DefKind::Trait, async_def_id);
+ bound_modifier_allowed_features = Some(features);
+ } else {
+ panic!();
+ }
+ } else {
+ panic!();
+ }
+ }
+
let path_span_lo = p.span.shrink_to_lo();
let proj_start = p.segments.len() - unresolved_segments;
let path = self.arena.alloc(hir::Path {
- res: self.lower_res(base_res),
+ res,
segments: self.arena.alloc_from_iter(p.segments[..proj_start].iter().enumerate().map(
|(i, segment)| {
let param_mode = match (qself_position, param_mode) {
@@ -77,7 +96,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
parenthesized_generic_args,
itctx,
// if this is the last segment, add constness to the trait path
- if i == proj_start - 1 { constness } else { None },
+ if i == proj_start - 1 { modifiers.map(|m| m.constness) } else { None },
+ bound_modifier_allowed_features.clone(),
)
},
)),
@@ -88,6 +108,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
),
});
+ if let Some(bound_modifier_allowed_features) = bound_modifier_allowed_features {
+ path.span = self.mark_span_with_reason(
+ DesugaringKind::BoundModifier,
+ path.span,
+ Some(bound_modifier_allowed_features),
+ );
+ }
+
// Simple case, either no projections, or only fully-qualified.
// E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
if unresolved_segments == 0 {
@@ -125,6 +153,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
ParenthesizedGenericArgs::Err,
itctx,
None,
+ None,
));
let qpath = hir::QPath::TypeRelative(ty, hir_segment);
@@ -166,6 +195,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
ParenthesizedGenericArgs::Err,
&ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
+ None,
)
})),
span: self.lower_span(p.span),
@@ -180,6 +210,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
parenthesized_generic_args: ParenthesizedGenericArgs,
itctx: &ImplTraitContext,
constness: Option<ast::BoundConstness>,
+ // Additional features ungated with a bound modifier like `async`.
+ // This is passed down to the implicit associated type binding in
+ // parenthesized bounds.
+ bound_modifier_allowed_features: Option<Lrc<[Symbol]>>,
) -> hir::PathSegment<'hir> {
debug!("path_span: {:?}, lower_path_segment(segment: {:?})", path_span, segment);
let (mut generic_args, infer_args) = if let Some(generic_args) = segment.args.as_deref() {
@@ -188,9 +222,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
}
GenericArgs::Parenthesized(data) => match parenthesized_generic_args {
- ParenthesizedGenericArgs::ParenSugar => {
- self.lower_parenthesized_parameter_data(data, itctx)
- }
+ ParenthesizedGenericArgs::ParenSugar => self
+ .lower_parenthesized_parameter_data(
+ data,
+ itctx,
+ bound_modifier_allowed_features,
+ ),
ParenthesizedGenericArgs::Err => {
// Suggest replacing parentheses with angle brackets `Trait(params...)` to `Trait<params...>`
let sub = if !data.inputs.is_empty() {
@@ -357,6 +394,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
&mut self,
data: &ParenthesizedArgs,
itctx: &ImplTraitContext,
+ bound_modifier_allowed_features: Option<Lrc<[Symbol]>>,
) -> (GenericArgsCtor<'hir>, bool) {
// Switch to `PassThrough` mode for anonymous lifetimes; this
// means that we permit things like `&Ref<T>`, where `Ref` has
@@ -392,7 +430,19 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
FnRetTy::Default(_) => self.arena.alloc(self.ty_tup(*span, &[])),
};
let args = smallvec![GenericArg::Type(self.arena.alloc(self.ty_tup(*inputs_span, inputs)))];
- let binding = self.assoc_ty_binding(sym::Output, output_ty.span, output_ty);
+
+ // If we have a bound like `async Fn() -> T`, make sure that we mark the
+ // `Output = T` associated type bound with the right feature gates.
+ let mut output_span = output_ty.span;
+ if let Some(bound_modifier_allowed_features) = bound_modifier_allowed_features {
+ output_span = self.mark_span_with_reason(
+ DesugaringKind::BoundModifier,
+ output_span,
+ Some(bound_modifier_allowed_features),
+ );
+ }
+ let binding = self.assoc_ty_binding(sym::Output, output_span, output_ty);
+
(
GenericArgsCtor {
args,
@@ -429,4 +479,23 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
kind,
}
}
+
+ /// When a bound is annotated with `async`, it signals to lowering that the trait
+ /// that the bound refers to should be mapped to the "async" flavor of the trait.
+ ///
+ /// This only needs to be done until we unify `AsyncFn` and `Fn` traits into one
+ /// that is generic over `async`ness, if that's ever possible, or modify the
+ /// lowering of `async Fn()` bounds to desugar to another trait like `LendingFn`.
+ fn map_trait_to_async_trait(&self, def_id: DefId) -> Option<(DefId, Lrc<[Symbol]>)> {
+ let lang_items = self.tcx.lang_items();
+ if Some(def_id) == lang_items.fn_trait() {
+ Some((lang_items.async_fn_trait()?, self.allow_async_fn_traits.clone()))
+ } else if Some(def_id) == lang_items.fn_mut_trait() {
+ Some((lang_items.async_fn_mut_trait()?, self.allow_async_fn_traits.clone()))
+ } else if Some(def_id) == lang_items.fn_once_trait() {
+ Some((lang_items.async_fn_once_trait()?, self.allow_async_fn_traits.clone()))
+ } else {
+ None
+ }
+ }
}
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index a6f6f0b29a0..731232bce65 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -8,6 +8,7 @@ mod item;
use crate::pp::Breaks::{Consistent, Inconsistent};
use crate::pp::{self, Breaks};
use crate::pprust::state::expr::FixupContext;
+use ast::TraitBoundModifiers;
use rustc_ast::attr::AttrIdGenerator;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, BinOpToken, CommentKind, Delimiter, Nonterminal, Token, TokenKind};
@@ -1590,18 +1591,28 @@ impl<'a> State<'a> {
}
match bound {
- GenericBound::Trait(tref, modifier) => {
- match modifier.constness {
+ GenericBound::Trait(
+ tref,
+ TraitBoundModifiers { constness, asyncness, polarity },
+ ) => {
+ match constness {
ast::BoundConstness::Never => {}
ast::BoundConstness::Always(_) | ast::BoundConstness::Maybe(_) => {
- self.word_space(modifier.constness.as_str());
+ self.word_space(constness.as_str());
}
}
- match modifier.polarity {
+ match asyncness {
+ ast::BoundAsyncness::Normal => {}
+ ast::BoundAsyncness::Async(_) => {
+ self.word_space(asyncness.as_str());
+ }
+ }
+
+ match polarity {
ast::BoundPolarity::Positive => {}
ast::BoundPolarity::Negative(_) | ast::BoundPolarity::Maybe(_) => {
- self.word(modifier.polarity.as_str());
+ self.word(polarity.as_str());
}
}
diff --git a/compiler/rustc_expand/src/build.rs b/compiler/rustc_expand/src/build.rs
index f9bfebee12e..5879e025e7d 100644
--- a/compiler/rustc_expand/src/build.rs
+++ b/compiler/rustc_expand/src/build.rs
@@ -141,6 +141,7 @@ impl<'a> ExtCtxt<'a> {
} else {
ast::BoundConstness::Never
},
+ asyncness: ast::BoundAsyncness::Normal,
},
)
}
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index a4fb92c67ac..72089dc2a91 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -8,14 +8,13 @@ use crate::errors::{
};
use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
-use ast::DUMMY_NODE_ID;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, Delimiter, Token, TokenKind};
use rustc_ast::util::case::Case;
use rustc_ast::{
- self as ast, BareFnTy, BoundConstness, BoundPolarity, FnRetTy, GenericBound, GenericBounds,
- GenericParam, Generics, Lifetime, MacCall, MutTy, Mutability, PolyTraitRef,
- TraitBoundModifiers, TraitObjectSyntax, Ty, TyKind,
+ self as ast, BareFnTy, BoundAsyncness, BoundConstness, BoundPolarity, FnRetTy, GenericBound,
+ GenericBounds, GenericParam, Generics, Lifetime, MacCall, MutTy, Mutability, PolyTraitRef,
+ TraitBoundModifiers, TraitObjectSyntax, Ty, TyKind, DUMMY_NODE_ID,
};
use rustc_errors::{Applicability, PResult};
use rustc_span::symbol::{kw, sym, Ident};
@@ -880,6 +879,13 @@ impl<'a> Parser<'a> {
BoundConstness::Never
};
+ let asyncness = if self.token.span.at_least_rust_2018() && self.eat_keyword(kw::Async) {
+ self.sess.gated_spans.gate(sym::async_closure, self.prev_token.span);
+ BoundAsyncness::Async(self.prev_token.span)
+ } else {
+ BoundAsyncness::Normal
+ };
+
let polarity = if self.eat(&token::Question) {
BoundPolarity::Maybe(self.prev_token.span)
} else if self.eat(&token::Not) {
@@ -889,7 +895,7 @@ impl<'a> Parser<'a> {
BoundPolarity::Positive
};
- Ok(TraitBoundModifiers { constness, polarity })
+ Ok(TraitBoundModifiers { constness, asyncness, polarity })
}
/// Parses a type bound according to:
diff --git a/compiler/rustc_span/src/hygiene.rs b/compiler/rustc_span/src/hygiene.rs
index 3d26efec5a6..527938daae4 100644
--- a/compiler/rustc_span/src/hygiene.rs
+++ b/compiler/rustc_span/src/hygiene.rs
@@ -1154,6 +1154,8 @@ pub enum DesugaringKind {
Await,
ForLoop,
WhileLoop,
+ /// `async Fn()` bound modifier
+ BoundModifier,
}
impl DesugaringKind {
@@ -1169,6 +1171,7 @@ impl DesugaringKind {
DesugaringKind::OpaqueTy => "`impl Trait`",
DesugaringKind::ForLoop => "`for` loop",
DesugaringKind::WhileLoop => "`while` loop",
+ DesugaringKind::BoundModifier => "trait bound modifier",
}
}
}
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index dbfc89c2d49..2dca9808ada 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -423,6 +423,7 @@ symbols! {
async_fn_mut,
async_fn_once,
async_fn_track_caller,
+ async_fn_traits,
async_for_loop,
async_iterator,
async_iterator_poll_next,
diff --git a/tests/ui/async-await/async-fn/sugar.rs b/tests/ui/async-await/async-fn/sugar.rs
new file mode 100644
index 00000000000..868fb799ae4
--- /dev/null
+++ b/tests/ui/async-await/async-fn/sugar.rs
@@ -0,0 +1,14 @@
+// edition: 2021
+// check-pass
+
+#![feature(async_closure)]
+
+async fn foo() {}
+
+async fn call_asyncly(f: impl async Fn(i32) -> i32) -> i32 {
+ f(1).await
+}
+
+fn main() {
+ let fut = call_asyncly(|x| async move { x + 1 });
+}
diff --git a/tests/ui/stats/hir-stats.stderr b/tests/ui/stats/hir-stats.stderr
index 8b9ec30db63..2c21c25d7c7 100644
--- a/tests/ui/stats/hir-stats.stderr
+++ b/tests/ui/stats/hir-stats.stderr
@@ -5,8 +5,8 @@ ast-stats-1 GenericArgs 40 ( 0.6%) 1 40
ast-stats-1 - AngleBracketed 40 ( 0.6%) 1
ast-stats-1 Crate 40 ( 0.6%) 1 40
ast-stats-1 ExprField 48 ( 0.7%) 1 48
-ast-stats-1 WherePredicate 56 ( 0.9%) 1 56
-ast-stats-1 - BoundPredicate 56 ( 0.9%) 1
+ast-stats-1 WherePredicate 56 ( 0.8%) 1 56
+ast-stats-1 - BoundPredicate 56 ( 0.8%) 1
ast-stats-1 Attribute 64 ( 1.0%) 2 32
ast-stats-1 - Normal 32 ( 0.5%) 1
ast-stats-1 - DocComment 32 ( 0.5%) 1
@@ -22,38 +22,38 @@ ast-stats-1 - MacCall 32 ( 0.5%) 1
ast-stats-1 - Expr 96 ( 1.5%) 3
ast-stats-1 Param 160 ( 2.4%) 4 40
ast-stats-1 Block 192 ( 2.9%) 6 32
-ast-stats-1 Variant 208 ( 3.2%) 2 104
-ast-stats-1 GenericBound 288 ( 4.4%) 4 72
-ast-stats-1 - Trait 288 ( 4.4%) 4
-ast-stats-1 AssocItem 352 ( 5.4%) 4 88
+ast-stats-1 Variant 208 ( 3.1%) 2 104
+ast-stats-1 GenericBound 352 ( 5.3%) 4 88
+ast-stats-1 - Trait 352 ( 5.3%) 4
+ast-stats-1 AssocItem 352 ( 5.3%) 4 88
ast-stats-1 - Type 176 ( 2.7%) 2
ast-stats-1 - Fn 176 ( 2.7%) 2
ast-stats-1 GenericParam 480 ( 7.3%) 5 96
-ast-stats-1 Pat 504 ( 7.7%) 7 72
+ast-stats-1 Pat 504 ( 7.6%) 7 72
ast-stats-1 - Struct 72 ( 1.1%) 1
ast-stats-1 - Wild 72 ( 1.1%) 1
-ast-stats-1 - Ident 360 ( 5.5%) 5
-ast-stats-1 Expr 576 ( 8.8%) 8 72
+ast-stats-1 - Ident 360 ( 5.4%) 5
+ast-stats-1 Expr 576 ( 8.7%) 8 72
ast-stats-1 - Path 72 ( 1.1%) 1
ast-stats-1 - Match 72 ( 1.1%) 1
ast-stats-1 - Struct 72 ( 1.1%) 1
ast-stats-1 - Lit 144 ( 2.2%) 2
ast-stats-1 - Block 216 ( 3.3%) 3
-ast-stats-1 PathSegment 720 (11.0%) 30 24
-ast-stats-1 Ty 896 (13.7%) 14 64
+ast-stats-1 PathSegment 720 (10.9%) 30 24
+ast-stats-1 Ty 896 (13.5%) 14 64
ast-stats-1 - Ptr 64 ( 1.0%) 1
ast-stats-1 - Ref 64 ( 1.0%) 1
-ast-stats-1 - ImplicitSelf 128 ( 2.0%) 2
-ast-stats-1 - Path 640 ( 9.8%) 10
-ast-stats-1 Item 1_224 (18.7%) 9 136
+ast-stats-1 - ImplicitSelf 128 ( 1.9%) 2
+ast-stats-1 - Path 640 ( 9.7%) 10
+ast-stats-1 Item 1_224 (18.5%) 9 136
ast-stats-1 - Trait 136 ( 2.1%) 1
ast-stats-1 - Enum 136 ( 2.1%) 1
ast-stats-1 - ForeignMod 136 ( 2.1%) 1
ast-stats-1 - Impl 136 ( 2.1%) 1
-ast-stats-1 - Fn 272 ( 4.2%) 2
+ast-stats-1 - Fn 272 ( 4.1%) 2
ast-stats-1 - Use 408 ( 6.2%) 3
ast-stats-1 ----------------------------------------------------------------
-ast-stats-1 Total 6_552
+ast-stats-1 Total 6_616
ast-stats-1
ast-stats-2 POST EXPANSION AST STATS
ast-stats-2 Name Accumulated Size Count Item Size
@@ -81,39 +81,39 @@ ast-stats-2 - Expr 96 ( 1.3%) 3
ast-stats-2 Param 160 ( 2.2%) 4 40
ast-stats-2 Block 192 ( 2.7%) 6 32
ast-stats-2 Variant 208 ( 2.9%) 2 104
-ast-stats-2 GenericBound 288 ( 4.0%) 4 72
-ast-stats-2 - Trait 288 ( 4.0%) 4
+ast-stats-2 GenericBound 352 ( 4.9%) 4 88
+ast-stats-2 - Trait 352 ( 4.9%) 4
ast-stats-2 AssocItem 352 ( 4.9%) 4 88
-ast-stats-2 - Type 176 ( 2.5%) 2
-ast-stats-2 - Fn 176 ( 2.5%) 2
+ast-stats-2 - Type 176 ( 2.4%) 2
+ast-stats-2 - Fn 176 ( 2.4%) 2
ast-stats-2 GenericParam 480 ( 6.7%) 5 96
ast-stats-2 Pat 504 ( 7.0%) 7 72
ast-stats-2 - Struct 72 ( 1.0%) 1
ast-stats-2 - Wild 72 ( 1.0%) 1
ast-stats-2 - Ident 360 ( 5.0%) 5
-ast-stats-2 Expr 648 ( 9.1%) 9 72
+ast-stats-2 Expr 648 ( 9.0%) 9 72
ast-stats-2 - Path 72 ( 1.0%) 1
ast-stats-2 - Match 72 ( 1.0%) 1
ast-stats-2 - Struct 72 ( 1.0%) 1
ast-stats-2 - InlineAsm 72 ( 1.0%) 1
ast-stats-2 - Lit 144 ( 2.0%) 2
ast-stats-2 - Block 216 ( 3.0%) 3
-ast-stats-2 PathSegment 792 (11.1%) 33 24
-ast-stats-2 Ty 896 (12.5%) 14 64
+ast-stats-2 PathSegment 792 (11.0%) 33 24
+ast-stats-2 Ty 896 (12.4%) 14 64
ast-stats-2 - Ptr 64 ( 0.9%) 1
ast-stats-2 - Ref 64 ( 0.9%) 1
ast-stats-2 - ImplicitSelf 128 ( 1.8%) 2
ast-stats-2 - Path 640 ( 8.9%) 10
-ast-stats-2 Item 1_496 (20.9%) 11 136
+ast-stats-2 Item 1_496 (20.7%) 11 136
ast-stats-2 - Trait 136 ( 1.9%) 1
ast-stats-2 - Enum 136 ( 1.9%) 1
ast-stats-2 - ExternCrate 136 ( 1.9%) 1
ast-stats-2 - ForeignMod 136 ( 1.9%) 1
ast-stats-2 - Impl 136 ( 1.9%) 1
ast-stats-2 - Fn 272 ( 3.8%) 2
-ast-stats-2 - Use 544 ( 7.6%) 4
+ast-stats-2 - Use 544 ( 7.5%) 4
ast-stats-2 ----------------------------------------------------------------
-ast-stats-2 Total 7_152
+ast-stats-2 Total 7_216
ast-stats-2
hir-stats HIR STATS
hir-stats Name Accumulated Size Count Item Size
From cd2fd34ca68f701ade233a980093ee4444f7da3a Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 26 Jan 2024 17:00:34 +0000
Subject: [PATCH 2/4] Add tests
---
tests/ui/async-await/async-fn/dyn-pos.rs | 14 +++
tests/ui/async-await/async-fn/dyn-pos.stderr | 87 +++++++++++++++++++
tests/ui/async-await/async-fn/edition-2015.rs | 8 ++
.../async-await/async-fn/edition-2015.stderr | 22 +++++
tests/ui/async-await/async-fn/impl-header.rs | 8 ++
.../async-await/async-fn/impl-header.stderr | 8 ++
tests/ui/async-await/async-fn/impl-trait.rs | 15 ++++
.../async-await/async-fn/method-call-pos.rs | 7 ++
.../async-fn/method-call-pos.stderr | 14 +++
9 files changed, 183 insertions(+)
create mode 100644 tests/ui/async-await/async-fn/dyn-pos.rs
create mode 100644 tests/ui/async-await/async-fn/dyn-pos.stderr
create mode 100644 tests/ui/async-await/async-fn/edition-2015.rs
create mode 100644 tests/ui/async-await/async-fn/edition-2015.stderr
create mode 100644 tests/ui/async-await/async-fn/impl-header.rs
create mode 100644 tests/ui/async-await/async-fn/impl-header.stderr
create mode 100644 tests/ui/async-await/async-fn/impl-trait.rs
create mode 100644 tests/ui/async-await/async-fn/method-call-pos.rs
create mode 100644 tests/ui/async-await/async-fn/method-call-pos.stderr
diff --git a/tests/ui/async-await/async-fn/dyn-pos.rs b/tests/ui/async-await/async-fn/dyn-pos.rs
new file mode 100644
index 00000000000..3201fb8dbf3
--- /dev/null
+++ b/tests/ui/async-await/async-fn/dyn-pos.rs
@@ -0,0 +1,14 @@
+// edition:2018
+
+#![feature(async_closure)]
+
+fn foo(x: &dyn async Fn()) {}
+//~^ ERROR the trait `AsyncFn` cannot be made into an object
+//~| ERROR the trait `AsyncFn` cannot be made into an object
+//~| ERROR the trait `AsyncFn` cannot be made into an object
+//~| ERROR the trait `AsyncFn` cannot be made into an object
+//~| ERROR the trait `AsyncFnMut` cannot be made into an object
+//~| ERROR the trait `AsyncFnMut` cannot be made into an object
+//~| ERROR the trait `AsyncFnMut` cannot be made into an object
+
+fn main() {}
diff --git a/tests/ui/async-await/async-fn/dyn-pos.stderr b/tests/ui/async-await/async-fn/dyn-pos.stderr
new file mode 100644
index 00000000000..c9323526516
--- /dev/null
+++ b/tests/ui/async-await/async-fn/dyn-pos.stderr
@@ -0,0 +1,87 @@
+error[E0038]: the trait `AsyncFn` cannot be made into an object
+ --> $DIR/dyn-pos.rs:5:16
+ |
+LL | fn foo(x: &dyn async Fn()) {}
+ | ^^^^^^^^^^ `AsyncFn` cannot be made into an object
+ |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+ --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
+ |
+ = note: the trait cannot be made into an object because it contains the generic associated type `CallFuture`
+
+error[E0038]: the trait `AsyncFnMut` cannot be made into an object
+ --> $DIR/dyn-pos.rs:5:16
+ |
+LL | fn foo(x: &dyn async Fn()) {}
+ | ^^^^^^^^^^ `AsyncFnMut` cannot be made into an object
+ |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+ --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
+ |
+ = note: the trait cannot be made into an object because it contains the generic associated type `CallMutFuture`
+
+error[E0038]: the trait `AsyncFn` cannot be made into an object
+ --> $DIR/dyn-pos.rs:5:16
+ |
+LL | fn foo(x: &dyn async Fn()) {}
+ | ^^^^^^^^^^ `AsyncFn` cannot be made into an object
+ |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+ --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
+ |
+ = note: the trait cannot be made into an object because it contains the generic associated type `CallFuture`
+ = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0038]: the trait `AsyncFnMut` cannot be made into an object
+ --> $DIR/dyn-pos.rs:5:16
+ |
+LL | fn foo(x: &dyn async Fn()) {}
+ | ^^^^^^^^^^ `AsyncFnMut` cannot be made into an object
+ |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+ --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
+ |
+ = note: the trait cannot be made into an object because it contains the generic associated type `CallMutFuture`
+ = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0038]: the trait `AsyncFn` cannot be made into an object
+ --> $DIR/dyn-pos.rs:5:16
+ |
+LL | fn foo(x: &dyn async Fn()) {}
+ | ^^^^^^^^^^ `AsyncFn` cannot be made into an object
+ |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+ --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
+ |
+ = note: the trait cannot be made into an object because it contains the generic associated type `CallFuture`
+ = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0038]: the trait `AsyncFnMut` cannot be made into an object
+ --> $DIR/dyn-pos.rs:5:16
+ |
+LL | fn foo(x: &dyn async Fn()) {}
+ | ^^^^^^^^^^ `AsyncFnMut` cannot be made into an object
+ |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+ --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
+ |
+ = note: the trait cannot be made into an object because it contains the generic associated type `CallMutFuture`
+ = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0038]: the trait `AsyncFn` cannot be made into an object
+ --> $DIR/dyn-pos.rs:5:12
+ |
+LL | fn foo(x: &dyn async Fn()) {}
+ | ^^^^^^^^^^^^^^ `AsyncFn` cannot be made into an object
+ |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+ --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
+ |
+ = note: the trait cannot be made into an object because it contains the generic associated type `CallFuture`
+ ::: $SRC_DIR/core/src/ops/async_function.rs:LL:COL
+ |
+ = note: the trait cannot be made into an object because it contains the generic associated type `CallMutFuture`
+
+error: aborting due to 7 previous errors
+
+For more information about this error, try `rustc --explain E0038`.
diff --git a/tests/ui/async-await/async-fn/edition-2015.rs b/tests/ui/async-await/async-fn/edition-2015.rs
new file mode 100644
index 00000000000..287d05ecacb
--- /dev/null
+++ b/tests/ui/async-await/async-fn/edition-2015.rs
@@ -0,0 +1,8 @@
+// FIXME(async_closures): This error message could be made better.
+
+fn foo(x: impl async Fn()) -> impl async Fn() {}
+//~^ ERROR expected
+//~| ERROR expected
+//~| ERROR expected
+
+fn main() {}
diff --git a/tests/ui/async-await/async-fn/edition-2015.stderr b/tests/ui/async-await/async-fn/edition-2015.stderr
new file mode 100644
index 00000000000..e79b92ccf9f
--- /dev/null
+++ b/tests/ui/async-await/async-fn/edition-2015.stderr
@@ -0,0 +1,22 @@
+error: expected one of `:` or `|`, found `)`
+ --> $DIR/edition-2015.rs:3:26
+ |
+LL | fn foo(x: impl async Fn()) -> impl async Fn() {}
+ | ^ expected one of `:` or `|`
+
+error: expected one of `(`, `)`, `+`, `,`, `::`, or `<`, found `Fn`
+ --> $DIR/edition-2015.rs:3:22
+ |
+LL | fn foo(x: impl async Fn()) -> impl async Fn() {}
+ | -^^ expected one of `(`, `)`, `+`, `,`, `::`, or `<`
+ | |
+ | help: missing `,`
+
+error: expected one of `(`, `+`, `::`, `<`, `where`, or `{`, found `Fn`
+ --> $DIR/edition-2015.rs:3:42
+ |
+LL | fn foo(x: impl async Fn()) -> impl async Fn() {}
+ | ^^ expected one of `(`, `+`, `::`, `<`, `where`, or `{`
+
+error: aborting due to 3 previous errors
+
diff --git a/tests/ui/async-await/async-fn/impl-header.rs b/tests/ui/async-await/async-fn/impl-header.rs
new file mode 100644
index 00000000000..fb1844384ae
--- /dev/null
+++ b/tests/ui/async-await/async-fn/impl-header.rs
@@ -0,0 +1,8 @@
+// edition:2018
+
+struct F;
+
+impl async Fn<()> for F {}
+//~^ ERROR expected type, found keyword `async`
+
+fn main() {}
diff --git a/tests/ui/async-await/async-fn/impl-header.stderr b/tests/ui/async-await/async-fn/impl-header.stderr
new file mode 100644
index 00000000000..02cb4326242
--- /dev/null
+++ b/tests/ui/async-await/async-fn/impl-header.stderr
@@ -0,0 +1,8 @@
+error: expected type, found keyword `async`
+ --> $DIR/impl-header.rs:5:6
+ |
+LL | impl async Fn<()> for F {}
+ | ^^^^^ expected type
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/async-await/async-fn/impl-trait.rs b/tests/ui/async-await/async-fn/impl-trait.rs
new file mode 100644
index 00000000000..97f6696fe14
--- /dev/null
+++ b/tests/ui/async-await/async-fn/impl-trait.rs
@@ -0,0 +1,15 @@
+// edition:2018
+// check-pass
+
+#![feature(async_closure, type_alias_impl_trait)]
+
+type Tait = impl async Fn();
+fn tait() -> Tait {
+ || async {}
+}
+
+fn foo(x: impl async Fn()) -> impl async Fn() { x }
+
+fn param<T: async Fn()>() {}
+
+fn main() {}
diff --git a/tests/ui/async-await/async-fn/method-call-pos.rs b/tests/ui/async-await/async-fn/method-call-pos.rs
new file mode 100644
index 00000000000..aaa0245b986
--- /dev/null
+++ b/tests/ui/async-await/async-fn/method-call-pos.rs
@@ -0,0 +1,7 @@
+// edition:2018
+
+fn main() {
+ <_ as async Fn()>(|| async {});
+ //~^ ERROR expected identifier, found keyword `async`
+ //~| ERROR expected one of
+}
diff --git a/tests/ui/async-await/async-fn/method-call-pos.stderr b/tests/ui/async-await/async-fn/method-call-pos.stderr
new file mode 100644
index 00000000000..527515a1b44
--- /dev/null
+++ b/tests/ui/async-await/async-fn/method-call-pos.stderr
@@ -0,0 +1,14 @@
+error: expected identifier, found keyword `async`
+ --> $DIR/method-call-pos.rs:4:11
+ |
+LL | <_ as async Fn()>(|| async {});
+ | ^^^^^ expected identifier, found keyword
+
+error: expected one of `(`, `::`, `<`, or `>`, found `Fn`
+ --> $DIR/method-call-pos.rs:4:17
+ |
+LL | <_ as async Fn()>(|| async {});
+ | ^^ expected one of `(`, `::`, `<`, or `>`
+
+error: aborting due to 2 previous errors
+
From 54db272cc972f232cc50a7c6dff30140f904738a Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 26 Jan 2024 17:15:43 +0000
Subject: [PATCH 3/4] Better error message in ed 2015
---
compiler/rustc_parse/messages.ftl | 2 +
compiler/rustc_parse/src/errors.rs | 9 ++++
compiler/rustc_parse/src/parser/ty.rs | 15 +++++-
.../async-fn/edition-2015-not-async-bound.rs | 10 ++++
tests/ui/async-await/async-fn/edition-2015.rs | 11 ++--
.../async-await/async-fn/edition-2015.stderr | 53 +++++++++++++------
6 files changed, 76 insertions(+), 24 deletions(-)
create mode 100644 tests/ui/async-await/async-fn/edition-2015-not-async-bound.rs
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index aac8c0b3103..7c2ecf34c17 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -22,6 +22,8 @@ parse_associated_static_item_not_allowed = associated `static` items are not all
parse_async_block_in_2015 = `async` blocks are only allowed in Rust 2018 or later
+parse_async_bound_modifier_in_2015 = `async` trait bounds are only allowed in Rust 2018 or later
+
parse_async_fn_in_2015 = `async fn` is not permitted in Rust 2015
.label = to use `async fn`, switch to Rust 2018 or later
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 4e4bf9bdad9..86a64d90deb 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -1588,6 +1588,15 @@ pub(crate) struct AsyncMoveBlockIn2015 {
pub span: Span,
}
+#[derive(Diagnostic)]
+#[diag(parse_async_bound_modifier_in_2015)]
+pub(crate) struct AsyncBoundModifierIn2015 {
+ #[primary_span]
+ pub span: Span,
+ #[subdiagnostic]
+ pub help: HelpUseLatestEdition,
+}
+
#[derive(Diagnostic)]
#[diag(parse_self_argument_pointer)]
pub(crate) struct SelfArgumentPointer {
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 72089dc2a91..5fe54a536a7 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -3,8 +3,8 @@ use super::{Parser, PathStyle, TokenType};
use crate::errors::{
self, DynAfterMut, ExpectedFnPathFoundFnKeyword, ExpectedMutOrConstInRawPointerType,
FnPointerCannotBeAsync, FnPointerCannotBeConst, FnPtrWithGenerics, FnPtrWithGenericsSugg,
- InvalidDynKeyword, LifetimeAfterMut, NeedPlusAfterTraitObjectLifetime, NestedCVariadicType,
- ReturnTypesUseThinArrow,
+ HelpUseLatestEdition, InvalidDynKeyword, LifetimeAfterMut, NeedPlusAfterTraitObjectLifetime,
+ NestedCVariadicType, ReturnTypesUseThinArrow,
};
use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
@@ -882,6 +882,17 @@ impl<'a> Parser<'a> {
let asyncness = if self.token.span.at_least_rust_2018() && self.eat_keyword(kw::Async) {
self.sess.gated_spans.gate(sym::async_closure, self.prev_token.span);
BoundAsyncness::Async(self.prev_token.span)
+ } else if self.may_recover()
+ && self.token.span.is_rust_2015()
+ && self.is_kw_followed_by_ident(kw::Async)
+ {
+ self.bump(); // eat `async`
+ self.dcx().emit_err(errors::AsyncBoundModifierIn2015 {
+ span: self.prev_token.span,
+ help: HelpUseLatestEdition::new(),
+ });
+ self.sess.gated_spans.gate(sym::async_closure, self.prev_token.span);
+ BoundAsyncness::Async(self.prev_token.span)
} else {
BoundAsyncness::Normal
};
diff --git a/tests/ui/async-await/async-fn/edition-2015-not-async-bound.rs b/tests/ui/async-await/async-fn/edition-2015-not-async-bound.rs
new file mode 100644
index 00000000000..6436787b665
--- /dev/null
+++ b/tests/ui/async-await/async-fn/edition-2015-not-async-bound.rs
@@ -0,0 +1,10 @@
+// check-pass
+// Make sure that we don't eagerly recover `async ::Bound` in edition 2015.
+
+mod async {
+ pub trait Foo {}
+}
+
+fn test(x: impl async ::Foo) {}
+
+fn main() {}
diff --git a/tests/ui/async-await/async-fn/edition-2015.rs b/tests/ui/async-await/async-fn/edition-2015.rs
index 287d05ecacb..83b9d415dda 100644
--- a/tests/ui/async-await/async-fn/edition-2015.rs
+++ b/tests/ui/async-await/async-fn/edition-2015.rs
@@ -1,8 +1,7 @@
-// FIXME(async_closures): This error message could be made better.
-
-fn foo(x: impl async Fn()) -> impl async Fn() {}
-//~^ ERROR expected
-//~| ERROR expected
-//~| ERROR expected
+fn foo(x: impl async Fn()) -> impl async Fn() { x }
+//~^ ERROR `async` trait bounds are only allowed in Rust 2018 or later
+//~| ERROR `async` trait bounds are only allowed in Rust 2018 or later
+//~| ERROR async closures are unstable
+//~| ERROR async closures are unstable
fn main() {}
diff --git a/tests/ui/async-await/async-fn/edition-2015.stderr b/tests/ui/async-await/async-fn/edition-2015.stderr
index e79b92ccf9f..0029d53868d 100644
--- a/tests/ui/async-await/async-fn/edition-2015.stderr
+++ b/tests/ui/async-await/async-fn/edition-2015.stderr
@@ -1,22 +1,43 @@
-error: expected one of `:` or `|`, found `)`
- --> $DIR/edition-2015.rs:3:26
+error: `async` trait bounds are only allowed in Rust 2018 or later
+ --> $DIR/edition-2015.rs:1:16
|
-LL | fn foo(x: impl async Fn()) -> impl async Fn() {}
- | ^ expected one of `:` or `|`
-
-error: expected one of `(`, `)`, `+`, `,`, `::`, or `<`, found `Fn`
- --> $DIR/edition-2015.rs:3:22
+LL | fn foo(x: impl async Fn()) -> impl async Fn() { x }
+ | ^^^^^
|
-LL | fn foo(x: impl async Fn()) -> impl async Fn() {}
- | -^^ expected one of `(`, `)`, `+`, `,`, `::`, or `<`
- | |
- | help: missing `,`
+ = help: pass `--edition 2021` to `rustc`
+ = note: for more on editions, read https://doc.rust-lang.org/edition-guide
-error: expected one of `(`, `+`, `::`, `<`, `where`, or `{`, found `Fn`
- --> $DIR/edition-2015.rs:3:42
+error: `async` trait bounds are only allowed in Rust 2018 or later
+ --> $DIR/edition-2015.rs:1:36
|
-LL | fn foo(x: impl async Fn()) -> impl async Fn() {}
- | ^^ expected one of `(`, `+`, `::`, `<`, `where`, or `{`
+LL | fn foo(x: impl async Fn()) -> impl async Fn() { x }
+ | ^^^^^
+ |
+ = help: pass `--edition 2021` to `rustc`
+ = note: for more on editions, read https://doc.rust-lang.org/edition-guide
-error: aborting due to 3 previous errors
+error[E0658]: async closures are unstable
+ --> $DIR/edition-2015.rs:1:16
+ |
+LL | fn foo(x: impl async Fn()) -> impl async Fn() { x }
+ | ^^^^^
+ |
+ = note: see issue #62290 <https://github.com/rust-lang/rust/issues/62290> for more information
+ = help: add `#![feature(async_closure)]` to the crate attributes to enable
+ = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ = help: to use an async block, remove the `||`: `async {`
+error[E0658]: async closures are unstable
+ --> $DIR/edition-2015.rs:1:36
+ |
+LL | fn foo(x: impl async Fn()) -> impl async Fn() { x }
+ | ^^^^^
+ |
+ = note: see issue #62290 <https://github.com/rust-lang/rust/issues/62290> for more information
+ = help: add `#![feature(async_closure)]` to the crate attributes to enable
+ = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ = help: to use an async block, remove the `||`: `async {`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0658`.
From 3913c9a0cacf4bacb4ca1c6255271d54ec995f02 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 26 Jan 2024 17:33:42 +0000
Subject: [PATCH 4/4] Error on incorrect item kind in async bound
---
compiler/rustc_ast_lowering/messages.ftl | 6 ++++
compiler/rustc_ast_lowering/src/errors.rs | 15 ++++++++++
compiler/rustc_ast_lowering/src/path.rs | 29 +++++++++++++------
tests/ui/async-await/async-fn/not-a-trait.rs | 13 +++++++++
.../async-await/async-fn/not-a-trait.stderr | 16 ++++++++++
tests/ui/async-await/async-fn/wrong-trait.rs | 10 +++++++
.../async-await/async-fn/wrong-trait.stderr | 8 +++++
7 files changed, 88 insertions(+), 9 deletions(-)
create mode 100644 tests/ui/async-await/async-fn/not-a-trait.rs
create mode 100644 tests/ui/async-await/async-fn/not-a-trait.stderr
create mode 100644 tests/ui/async-await/async-fn/wrong-trait.rs
create mode 100644 tests/ui/async-await/async-fn/wrong-trait.stderr
diff --git a/compiler/rustc_ast_lowering/messages.ftl b/compiler/rustc_ast_lowering/messages.ftl
index 8615016cda5..e0dc227ca4c 100644
--- a/compiler/rustc_ast_lowering/messages.ftl
+++ b/compiler/rustc_ast_lowering/messages.ftl
@@ -11,6 +11,12 @@ ast_lowering_argument = argument
ast_lowering_assoc_ty_parentheses =
parenthesized generic arguments cannot be used in associated type constraints
+ast_lowering_async_bound_not_on_trait =
+ `async` bound modifier only allowed on trait, not `{$descr}`
+
+ast_lowering_async_bound_only_for_fn_traits =
+ `async` bound modifier only allowed on `Fn`/`FnMut`/`FnOnce` traits
+
ast_lowering_async_coroutines_not_supported =
`async` coroutines are not yet supported
diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs
index 51bb8a96fad..7658dfa5d5f 100644
--- a/compiler/rustc_ast_lowering/src/errors.rs
+++ b/compiler/rustc_ast_lowering/src/errors.rs
@@ -395,3 +395,18 @@ pub(crate) struct GenericParamDefaultInBinder {
#[primary_span]
pub span: Span,
}
+
+#[derive(Diagnostic)]
+#[diag(ast_lowering_async_bound_not_on_trait)]
+pub(crate) struct AsyncBoundNotOnTrait {
+ #[primary_span]
+ pub span: Span,
+ pub descr: &'static str,
+}
+
+#[derive(Diagnostic)]
+#[diag(ast_lowering_async_bound_only_for_fn_traits)]
+pub(crate) struct AsyncBoundOnlyForFnTraits {
+ #[primary_span]
+ pub span: Span,
+}
diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index b4f1d7ce8c2..b58ac5c3dae 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -1,6 +1,8 @@
use crate::ImplTraitPosition;
-use super::errors::{GenericTypeWithParentheses, UseAngleBrackets};
+use super::errors::{
+ AsyncBoundNotOnTrait, AsyncBoundOnlyForFnTraits, GenericTypeWithParentheses, UseAngleBrackets,
+};
use super::ResolverAstLoweringExt;
use super::{GenericArgsCtor, LifetimeRes, ParenthesizedGenericArgs};
use super::{ImplTraitContext, LoweringContext, ParamMode};
@@ -42,15 +44,24 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
// When we have an `async` kw on a bound, map the trait it resolves to.
let mut bound_modifier_allowed_features = None;
if let Some(TraitBoundModifiers { asyncness: BoundAsyncness::Async(_), .. }) = modifiers {
- if let Res::Def(DefKind::Trait, def_id) = res {
- if let Some((async_def_id, features)) = self.map_trait_to_async_trait(def_id) {
- res = Res::Def(DefKind::Trait, async_def_id);
- bound_modifier_allowed_features = Some(features);
- } else {
- panic!();
+ match res {
+ Res::Def(DefKind::Trait, def_id) => {
+ if let Some((async_def_id, features)) = self.map_trait_to_async_trait(def_id) {
+ res = Res::Def(DefKind::Trait, async_def_id);
+ bound_modifier_allowed_features = Some(features);
+ } else {
+ self.dcx().emit_err(AsyncBoundOnlyForFnTraits { span: p.span });
+ }
+ }
+ Res::Err => {
+ // No additional error.
+ }
+ _ => {
+ // This error isn't actually emitted AFAICT, but it's best to keep
+ // it around in case the resolver doesn't always check the defkind
+ // of an item or something.
+ self.dcx().emit_err(AsyncBoundNotOnTrait { span: p.span, descr: res.descr() });
}
- } else {
- panic!();
}
}
diff --git a/tests/ui/async-await/async-fn/not-a-trait.rs b/tests/ui/async-await/async-fn/not-a-trait.rs
new file mode 100644
index 00000000000..a8fa21e5568
--- /dev/null
+++ b/tests/ui/async-await/async-fn/not-a-trait.rs
@@ -0,0 +1,13 @@
+// edition:2018
+
+#![feature(async_closure)]
+
+struct S;
+
+fn test(x: impl async S) {}
+//~^ ERROR expected trait, found struct `S`
+
+fn missing(x: impl async Missing) {}
+//~^ ERROR cannot find trait `Missing` in this scope
+
+fn main() {}
diff --git a/tests/ui/async-await/async-fn/not-a-trait.stderr b/tests/ui/async-await/async-fn/not-a-trait.stderr
new file mode 100644
index 00000000000..d49f7d7d2fc
--- /dev/null
+++ b/tests/ui/async-await/async-fn/not-a-trait.stderr
@@ -0,0 +1,16 @@
+error[E0404]: expected trait, found struct `S`
+ --> $DIR/not-a-trait.rs:7:23
+ |
+LL | fn test(x: impl async S) {}
+ | ^ not a trait
+
+error[E0405]: cannot find trait `Missing` in this scope
+ --> $DIR/not-a-trait.rs:10:26
+ |
+LL | fn missing(x: impl async Missing) {}
+ | ^^^^^^^ not found in this scope
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0404, E0405.
+For more information about an error, try `rustc --explain E0404`.
diff --git a/tests/ui/async-await/async-fn/wrong-trait.rs b/tests/ui/async-await/async-fn/wrong-trait.rs
new file mode 100644
index 00000000000..c431a362b1e
--- /dev/null
+++ b/tests/ui/async-await/async-fn/wrong-trait.rs
@@ -0,0 +1,10 @@
+// edition:2018
+
+#![feature(async_closure)]
+
+trait Foo {}
+
+fn test(x: impl async Foo) {}
+//~^ ERROR `async` bound modifier only allowed on `Fn`/`FnMut`/`FnOnce` traits
+
+fn main() {}
diff --git a/tests/ui/async-await/async-fn/wrong-trait.stderr b/tests/ui/async-await/async-fn/wrong-trait.stderr
new file mode 100644
index 00000000000..b39f5aa623c
--- /dev/null
+++ b/tests/ui/async-await/async-fn/wrong-trait.stderr
@@ -0,0 +1,8 @@
+error: `async` bound modifier only allowed on `Fn`/`FnMut`/`FnOnce` traits
+ --> $DIR/wrong-trait.rs:7:23
+ |
+LL | fn test(x: impl async Foo) {}
+ | ^^^
+
+error: aborting due to 1 previous error
+