dnrops
/
rust
mirror of https://github.com/rust-lang/rust.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Implement `async gen` blocks

This commit is contained in:
Michael Goulet 2023-11-28 18:18:19 +00:00
parent a0cbc168c9
commit 96bb542a31
32 changed files with 563 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
compiler/rustc_ast/src/ast.rs
View File

@ -1516,6 +1516,7 @@ pub enum ExprKind {
pub enum GenBlockKind {
Async,
Gen,
AsyncGen,
}
impl fmt::Display for GenBlockKind {
@ -1529,6 +1530,7 @@ impl GenBlockKind {
match self {
GenBlockKind::Async => "async",
GenBlockKind::Gen => "gen",
GenBlockKind::AsyncGen => "async gen",
}
}
}

141
compiler/rustc_ast_lowering/src/expr.rs
View File

@ -324,6 +324,15 @@ impl<'hir> LoweringContext<'_, 'hir> {
hir::CoroutineSource::Block,
|this| this.with_new_scopes(e.span, |this| this.lower_block_expr(block)),
),
ExprKind::Gen(capture_clause, block, GenBlockKind::AsyncGen) => self
.make_async_gen_expr(
*capture_clause,
e.id,
None,
e.span,
hir::CoroutineSource::Block,
|this| this.with_new_scopes(e.span, |this| this.lower_block_expr(block)),
),
ExprKind::Yield(opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
ExprKind::Err => hir::ExprKind::Err(
self.tcx.sess.span_delayed_bug(e.span, "lowered ExprKind::Err"),
@ -706,6 +715,87 @@ impl<'hir> LoweringContext<'_, 'hir> {
}))
}
/// Lower a `async gen` construct to a generator that implements `AsyncIterator`.
///
/// This results in:
///
/// ```text
/// static move? |_task_context| -> () {
/// <body>
/// }
/// ```
pub(super) fn make_async_gen_expr(
&mut self,
capture_clause: CaptureBy,
closure_node_id: NodeId,
_yield_ty: Option<hir::FnRetTy<'hir>>,
span: Span,
async_coroutine_source: hir::CoroutineSource,
body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
) -> hir::ExprKind<'hir> {
let output = hir::FnRetTy::DefaultReturn(self.lower_span(span));
// Resume argument type: `ResumeTy`
let unstable_span = self.mark_span_with_reason(
DesugaringKind::Async,
span,
Some(self.allow_gen_future.clone()),
);
let resume_ty = hir::QPath::LangItem(hir::LangItem::ResumeTy, unstable_span);
let input_ty = hir::Ty {
hir_id: self.next_id(),
kind: hir::TyKind::Path(resume_ty),
span: unstable_span,
};
// The closure/coroutine `FnDecl` takes a single (resume) argument of type `input_ty`.
let fn_decl = self.arena.alloc(hir::FnDecl {
inputs: arena_vec![self; input_ty],
output,
c_variadic: false,
implicit_self: hir::ImplicitSelfKind::None,
lifetime_elision_allowed: false,
});
// Lower the argument pattern/ident. The ident is used again in the `.await` lowering.
let (pat, task_context_hid) = self.pat_ident_binding_mode(
span,
Ident::with_dummy_span(sym::_task_context),
hir::BindingAnnotation::MUT,
);
let param = hir::Param {
hir_id: self.next_id(),
pat,
ty_span: self.lower_span(span),
span: self.lower_span(span),
};
let params = arena_vec![self; param];
let body = self.lower_body(move |this| {
this.coroutine_kind = Some(hir::CoroutineKind::AsyncGen(async_coroutine_source));
let old_ctx = this.task_context;
this.task_context = Some(task_context_hid);
let res = body(this);
this.task_context = old_ctx;
(params, res)
});
// `static |_task_context| -> <ret_ty> { body }`:
hir::ExprKind::Closure(self.arena.alloc(hir::Closure {
def_id: self.local_def_id(closure_node_id),
binder: hir::ClosureBinder::Default,
capture_clause,
bound_generic_params: &[],
fn_decl,
body,
fn_decl_span: self.lower_span(span),
fn_arg_span: None,
movability: Some(hir::Movability::Static),
constness: hir::Constness::NotConst,
}))
}
/// Forwards a possible `#[track_caller]` annotation from `outer_hir_id` to
/// `inner_hir_id` in case the `async_fn_track_caller` feature is enabled.
pub(super) fn maybe_forward_track_caller(
@ -755,15 +845,18 @@ impl<'hir> LoweringContext<'_, 'hir> {
/// ```
fn lower_expr_await(&mut self, await_kw_span: Span, expr: &Expr) -> hir::ExprKind<'hir> {
let full_span = expr.span.to(await_kw_span);
match self.coroutine_kind {
Some(hir::CoroutineKind::Async(_)) => {}
let is_async_gen = match self.coroutine_kind {
Some(hir::CoroutineKind::Async(_)) => false,
Some(hir::CoroutineKind::AsyncGen(_)) => true,
Some(hir::CoroutineKind::Coroutine) | Some(hir::CoroutineKind::Gen(_)) | None => {
return hir::ExprKind::Err(self.tcx.sess.emit_err(AwaitOnlyInAsyncFnAndBlocks {
await_kw_span,
item_span: self.current_item,
}));
}
}
};
let span = self.mark_span_with_reason(DesugaringKind::Await, await_kw_span, None);
let gen_future_span = self.mark_span_with_reason(
DesugaringKind::Await,
@ -852,12 +945,19 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.stmt_expr(span, match_expr)
};
// task_context = yield ();
// Depending on `async` of `async gen`:
// async - task_context = yield ();
// async gen - task_context = yield ASYNC_GEN_PENDING;
let yield_stmt = {
let unit = self.expr_unit(span);
let yielded = if is_async_gen {
self.arena.alloc(self.expr_lang_item_path(span, hir::LangItem::AsyncGenPending))
} else {
self.expr_unit(span)
};
let yield_expr = self.expr(
span,
hir::ExprKind::Yield(unit, hir::YieldSource::Await { expr: Some(expr_hir_id) }),
hir::ExprKind::Yield(yielded, hir::YieldSource::Await { expr: Some(expr_hir_id) }),
);
let yield_expr = self.arena.alloc(yield_expr);
@ -967,7 +1067,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
Some(movability)
}
Some(hir::CoroutineKind::Gen(_)) | Some(hir::CoroutineKind::Async(_)) => {
Some(
hir::CoroutineKind::Gen(_)
| hir::CoroutineKind::Async(_)
| hir::CoroutineKind::AsyncGen(_),
) => {
panic!("non-`async`/`gen` closure body turned `async`/`gen` during lowering");
}
None => {
@ -1474,8 +1578,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
fn lower_expr_yield(&mut self, span: Span, opt_expr: Option<&Expr>) -> hir::ExprKind<'hir> {
match self.coroutine_kind {
Some(hir::CoroutineKind::Gen(_)) => {}
let is_async_gen = match self.coroutine_kind {
Some(hir::CoroutineKind::Gen(_)) => false,
Some(hir::CoroutineKind::AsyncGen(_)) => true,
Some(hir::CoroutineKind::Async(_)) => {
return hir::ExprKind::Err(
self.tcx.sess.emit_err(AsyncCoroutinesNotSupported { span }),
@ -1491,14 +1596,24 @@ impl<'hir> LoweringContext<'_, 'hir> {
)
.emit();
}
self.coroutine_kind = Some(hir::CoroutineKind::Coroutine)
self.coroutine_kind = Some(hir::CoroutineKind::Coroutine);
false
}
}
};
let expr =
let mut yielded =
opt_expr.as_ref().map(|x| self.lower_expr(x)).unwrap_or_else(|| self.expr_unit(span));
hir::ExprKind::Yield(expr, hir::YieldSource::Yield)
if is_async_gen {
// yield async_gen_ready($expr);
yielded = self.expr_call_lang_item_fn(
span,
hir::LangItem::AsyncGenReady,
std::slice::from_ref(yielded),
);
}
hir::ExprKind::Yield(yielded, hir::YieldSource::Yield)
}
/// Desugar `ExprForLoop` from: `[opt_ident]: for <pat> in <head> <body>` into:

15
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
View File

@ -2517,12 +2517,23 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
CoroutineKind::Gen(kind) => match kind {
CoroutineSource::Block => "gen block",
CoroutineSource::Closure => "gen closure",
_ => bug!("gen block/closure expected, but gen function found."),
CoroutineSource::Fn => {
bug!("gen block/closure expected, but gen function found.")
}
},
CoroutineKind::AsyncGen(kind) => match kind {
CoroutineSource::Block => "async gen block",
CoroutineSource::Closure => "async gen closure",
CoroutineSource::Fn => {
bug!("gen block/closure expected, but gen function found.")
}
},
CoroutineKind::Async(async_kind) => match async_kind {
CoroutineSource::Block => "async block",
CoroutineSource::Closure => "async closure",
_ => bug!("async block/closure expected, but async function found."),
CoroutineSource::Fn => {
bug!("async block/closure expected, but async function found.")
}
},
CoroutineKind::Coroutine => "coroutine",
},

19
compiler/rustc_borrowck/src/diagnostics/region_name.rs
View File

@ -684,7 +684,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
hir::FnRetTy::Return(hir_ty) => (fn_decl.output.span(), Some(hir_ty)),
};
let mir_description = match hir.body(body).coroutine_kind {
Some(hir::CoroutineKind::Async(gen)) => match gen {
Some(hir::CoroutineKind::Async(src)) => match src {
hir::CoroutineSource::Block => " of async block",
hir::CoroutineSource::Closure => " of async closure",
hir::CoroutineSource::Fn => {
@ -701,7 +701,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
" of async function"
}
},
Some(hir::CoroutineKind::Gen(gen)) => match gen {
Some(hir::CoroutineKind::Gen(src)) => match src {
hir::CoroutineSource::Block => " of gen block",
hir::CoroutineSource::Closure => " of gen closure",
hir::CoroutineSource::Fn => {
@ -715,6 +715,21 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
" of gen function"
}
},
Some(hir::CoroutineKind::AsyncGen(src)) => match src {
hir::CoroutineSource::Block => " of async gen block",
hir::CoroutineSource::Closure => " of async gen closure",
hir::CoroutineSource::Fn => {
let parent_item =
hir.get_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
let output = &parent_item
.fn_decl()
.expect("coroutine lowered from async gen fn should be in fn")
.output;
span = output.span();
" of async gen function"
}
},
Some(hir::CoroutineKind::Coroutine) => " of coroutine",
None => " of closure",
};

3
compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
View File

@ -566,6 +566,9 @@ fn coroutine_kind_label(coroutine_kind: Option<CoroutineKind>) -> &'static str {
Some(CoroutineKind::Async(CoroutineSource::Block)) => "async_block",
Some(CoroutineKind::Async(CoroutineSource::Closure)) => "async_closure",
Some(CoroutineKind::Async(CoroutineSource::Fn)) => "async_fn",
Some(CoroutineKind::AsyncGen(CoroutineSource::Block)) => "async_gen_block",
Some(CoroutineKind::AsyncGen(CoroutineSource::Closure)) => "async_gen_closure",
Some(CoroutineKind::AsyncGen(CoroutineSource::Fn)) => "async_gen_fn",
Some(CoroutineKind::Coroutine) => "coroutine",
None => "closure",
}

6
compiler/rustc_codegen_ssa/src/mir/locals.rs
View File

@ -43,7 +43,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
let local = mir::Local::from_usize(local);
let expected_ty = self.monomorphize(self.mir.local_decls[local].ty);
if expected_ty != op.layout.ty {
warn!("Unexpected initial operand type. See the issues/114858");
warn!(
"Unexpected initial operand type: expected {expected_ty:?}, found {:?}.\
See <https://github.com/rust-lang/rust/issues/114858>.",
op.layout.ty
);
}
}
}

25
compiler/rustc_hir/src/hir.rs
View File

@ -1339,12 +1339,16 @@ impl<'hir> Body<'hir> {
/// The type of source expression that caused this coroutine to be created.
#[derive(Clone, PartialEq, Eq, Debug, Copy, Hash, HashStable_Generic, Encodable, Decodable)]
pub enum CoroutineKind {
/// An explicit `async` block or the body of an async function.
/// An explicit `async` block or the body of an `async` function.
Async(CoroutineSource),
/// An explicit `gen` block or the body of a `gen` function.
Gen(CoroutineSource),
/// An explicit `async gen` block or the body of an `async gen` function,
/// which is able to both `yield` and `.await`.
AsyncGen(CoroutineSource),
/// A coroutine literal created via a `yield` inside a closure.
Coroutine,
}
@ -1369,6 +1373,14 @@ impl fmt::Display for CoroutineKind {
}
k.fmt(f)
}
CoroutineKind::AsyncGen(k) => {
if f.alternate() {
f.write_str("`async gen` ")?;
} else {
f.write_str("async gen ")?
}
k.fmt(f)
}
}
}
}
@ -2064,17 +2076,6 @@ impl fmt::Display for YieldSource {
}
}
impl From<CoroutineKind> for YieldSource {
fn from(kind: CoroutineKind) -> Self {
match kind {
// Guess based on the kind of the current coroutine.
CoroutineKind::Coroutine => Self::Yield,
CoroutineKind::Async(_) => Self::Await { expr: None },
CoroutineKind::Gen(_) => Self::Yield,
}
}
}
// N.B., if you change this, you'll probably want to change the corresponding
// type structure in middle/ty.rs as well.
#[derive(Debug, Clone, Copy, HashStable_Generic)]

5
compiler/rustc_hir/src/lang_items.rs
View File

@ -212,6 +212,7 @@ language_item_table! {
Iterator, sym::iterator, iterator_trait, Target::Trait, GenericRequirement::Exact(0);
Future, sym::future_trait, future_trait, Target::Trait, GenericRequirement::Exact(0);
AsyncIterator, sym::async_iterator, async_iterator_trait, Target::Trait, GenericRequirement::Exact(0);
CoroutineState, sym::coroutine_state, coroutine_state, Target::Enum, GenericRequirement::None;
Coroutine, sym::coroutine, coroutine_trait, Target::Trait, GenericRequirement::Minimum(1);
Unpin, sym::unpin, unpin_trait, Target::Trait, GenericRequirement::None;
@ -294,6 +295,10 @@ language_item_table! {
PollReady, sym::Ready, poll_ready_variant, Target::Variant, GenericRequirement::None;
PollPending, sym::Pending, poll_pending_variant, Target::Variant, GenericRequirement::None;
AsyncGenReady, sym::AsyncGenReady, async_gen_ready, Target::Method(MethodKind::Inherent), GenericRequirement::Exact(1);
AsyncGenPending, sym::AsyncGenPending, async_gen_pending, Target::AssocConst, GenericRequirement::Exact(1);
AsyncGenFinished, sym::AsyncGenFinished, async_gen_finished, Target::AssocConst, GenericRequirement::Exact(1);
// FIXME(swatinem): the following lang items are used for async lowering and
// should become obsolete eventually.
ResumeTy, sym::ResumeTy, resume_ty, Target::Struct, GenericRequirement::None;

4
compiler/rustc_hir_typeck/src/check.rs
View File

@ -59,7 +59,9 @@ pub(super) fn check_fn<'a, 'tcx>(
&& can_be_coroutine.is_some()
{
let yield_ty = match kind {
hir::CoroutineKind::Gen(..) | hir::CoroutineKind::Coroutine => {
hir::CoroutineKind::Gen(..)
| hir::CoroutineKind::AsyncGen(..)
| hir::CoroutineKind::Coroutine => {
let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::TypeInference,
span,

1
compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
View File

@ -763,6 +763,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let args = self.fresh_args_for_item(span, def_id);
let ty = item_ty.instantiate(self.tcx, args);
self.write_args(hir_id, args);
self.write_resolution(hir_id, Ok((def_kind, def_id)));
let code = match lang_item {

8
compiler/rustc_middle/src/mir/terminator.rs
View File

@ -150,11 +150,17 @@ impl<O> AssertKind<O> {
RemainderByZero(_) => "attempt to calculate the remainder with a divisor of zero",
ResumedAfterReturn(CoroutineKind::Coroutine) => "coroutine resumed after completion",
ResumedAfterReturn(CoroutineKind::Async(_)) => "`async fn` resumed after completion",
ResumedAfterReturn(CoroutineKind::AsyncGen(_)) => {
"`async gen fn` resumed after completion"
}
ResumedAfterReturn(CoroutineKind::Gen(_)) => {
"`gen fn` should just keep returning `None` after completion"
}
ResumedAfterPanic(CoroutineKind::Coroutine) => "coroutine resumed after panicking",
ResumedAfterPanic(CoroutineKind::Async(_)) => "`async fn` resumed after panicking",
ResumedAfterPanic(CoroutineKind::AsyncGen(_)) => {
"`async gen fn` resumed after panicking"
}
ResumedAfterPanic(CoroutineKind::Gen(_)) => {
"`gen fn` should just keep returning `None` after panicking"
}
@ -245,6 +251,7 @@ impl<O> AssertKind<O> {
DivisionByZero(_) => middle_assert_divide_by_zero,
RemainderByZero(_) => middle_assert_remainder_by_zero,
ResumedAfterReturn(CoroutineKind::Async(_)) => middle_assert_async_resume_after_return,
ResumedAfterReturn(CoroutineKind::AsyncGen(_)) => todo!(),
ResumedAfterReturn(CoroutineKind::Gen(_)) => {
bug!("gen blocks can be resumed after they return and will keep returning `None`")
}
@ -252,6 +259,7 @@ impl<O> AssertKind<O> {
middle_assert_coroutine_resume_after_return
}
ResumedAfterPanic(CoroutineKind::Async(_)) => middle_assert_async_resume_after_panic,
ResumedAfterPanic(CoroutineKind::AsyncGen(_)) => todo!(),
ResumedAfterPanic(CoroutineKind::Gen(_)) => middle_assert_gen_resume_after_panic,
ResumedAfterPanic(CoroutineKind::Coroutine) => {
middle_assert_coroutine_resume_after_panic

8
compiler/rustc_middle/src/traits/select.rs
View File

@ -144,10 +144,14 @@ pub enum SelectionCandidate<'tcx> {
/// generated for an async construct.
FutureCandidate,
/// Implementation of an `Iterator` trait by one of the generator types
/// generated for a gen construct.
/// Implementation of an `Iterator` trait by one of the coroutine types
/// generated for a `gen` construct.
IteratorCandidate,
/// Implementation of an `AsyncIterator` trait by one of the coroutine types
/// generated for a `async gen` construct.
AsyncIteratorCandidate,
/// Implementation of a `Fn`-family trait by one of the anonymous
/// types generated for a fn pointer type (e.g., `fn(int) -> int`)
FnPointerCandidate {

7
compiler/rustc_middle/src/ty/context.rs
View File

@ -825,11 +825,16 @@ impl<'tcx> TyCtxt<'tcx> {
matches!(self.coroutine_kind(def_id), Some(hir::CoroutineKind::Coroutine))
}
/// Returns `true` if the node pointed to by `def_id` is a coroutine for a gen construct.
/// Returns `true` if the node pointed to by `def_id` is a coroutine for a `gen` construct.
pub fn coroutine_is_gen(self, def_id: DefId) -> bool {
matches!(self.coroutine_kind(def_id), Some(hir::CoroutineKind::Gen(_)))
}
/// Returns `true` if the node pointed to by `def_id` is a coroutine for a `async gen` construct.
pub fn coroutine_is_async_gen(self, def_id: DefId) -> bool {
matches!(self.coroutine_kind(def_id), Some(hir::CoroutineKind::AsyncGen(_)))
}
pub fn stability(self) -> &'tcx stability::Index {
self.stability_index(())
}

2
compiler/rustc_middle/src/ty/util.rs
View File

@ -732,6 +732,7 @@ impl<'tcx> TyCtxt<'tcx> {
DefKind::Closure if let Some(coroutine_kind) = self.coroutine_kind(def_id) => {
match coroutine_kind {
rustc_hir::CoroutineKind::Async(..) => "async closure",
rustc_hir::CoroutineKind::AsyncGen(..) => "async gen closure",
rustc_hir::CoroutineKind::Coroutine => "coroutine",
rustc_hir::CoroutineKind::Gen(..) => "gen closure",
}
@ -752,6 +753,7 @@ impl<'tcx> TyCtxt<'tcx> {
DefKind::Closure if let Some(coroutine_kind) = self.coroutine_kind(def_id) => {
match coroutine_kind {
rustc_hir::CoroutineKind::Async(..) => "an",
rustc_hir::CoroutineKind::AsyncGen(..) => "an",
rustc_hir::CoroutineKind::Coroutine => "a",
rustc_hir::CoroutineKind::Gen(..) => "a",
}

30
compiler/rustc_mir_transform/src/coroutine.rs
View File

@ -355,6 +355,26 @@ impl<'tcx> TransformVisitor<'tcx> {
)
}
}
CoroutineKind::AsyncGen(_) => {
if is_return {
let ty::Adt(_poll_adt, args) = *self.old_yield_ty.kind() else { bug!() };
let ty::Adt(_option_adt, args) = *args.type_at(0).kind() else { bug!() };
let yield_ty = args.type_at(0);
Rvalue::Use(Operand::Constant(Box::new(ConstOperand {
span: source_info.span,
const_: Const::Unevaluated(
UnevaluatedConst::new(
self.tcx.require_lang_item(LangItem::AsyncGenFinished, None),
self.tcx.mk_args(&[yield_ty.into()]),
),
self.old_yield_ty,
),
user_ty: None,
})))
} else {
Rvalue::Use(val)
}
}
CoroutineKind::Coroutine => {
let coroutine_state_def_id =
self.tcx.require_lang_item(LangItem::CoroutineState, None);
@ -1373,7 +1393,8 @@ fn create_coroutine_resume_function<'tcx>(
if can_return {
let block = match coroutine_kind {
CoroutineKind::Async(_) | CoroutineKind::Coroutine => {
// FIXME(gen_blocks): Should `async gen` yield `None` when resumed once again?
CoroutineKind::Async(_) | CoroutineKind::AsyncGen(_) | CoroutineKind::Coroutine => {
insert_panic_block(tcx, body, ResumedAfterReturn(coroutine_kind))
}
CoroutineKind::Gen(_) => transform.insert_none_ret_block(body),
@ -1562,6 +1583,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
};
let is_async_kind = matches!(body.coroutine_kind(), Some(CoroutineKind::Async(_)));
let is_async_gen_kind = matches!(body.coroutine_kind(), Some(CoroutineKind::AsyncGen(_)));
let is_gen_kind = matches!(body.coroutine_kind(), Some(CoroutineKind::Gen(_)));
let new_ret_ty = match body.coroutine_kind().unwrap() {
CoroutineKind::Async(_) => {
@ -1578,6 +1600,10 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
let option_args = tcx.mk_args(&[old_yield_ty.into()]);
Ty::new_adt(tcx, option_adt_ref, option_args)
}
CoroutineKind::AsyncGen(_) => {
// The yield ty is already `Poll<Option<yield_ty>>`
old_yield_ty
}
CoroutineKind::Coroutine => {
// Compute CoroutineState<yield_ty, return_ty>
let state_did = tcx.require_lang_item(LangItem::CoroutineState, None);
@ -1592,7 +1618,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
let old_ret_local = replace_local(RETURN_PLACE, new_ret_ty, body, tcx);
// Replace all occurrences of `ResumeTy` with `&mut Context<'_>` within async bodies.
if is_async_kind {
if is_async_kind || is_async_gen_kind {
transform_async_context(tcx, body);
}

23
compiler/rustc_parse/src/parser/expr.rs
View File

@ -1442,8 +1442,9 @@ impl<'a> Parser<'a> {
} else if this.token.uninterpolated_span().at_least_rust_2018() {
// `Span:.at_least_rust_2018()` is somewhat expensive; don't get it repeatedly.
if this.check_keyword(kw::Async) {
if this.is_gen_block(kw::Async) {
// Check for `async {` and `async move {`.
if this.is_gen_block(kw::Async, 0) || this.is_gen_block(kw::Gen, 1) {
// Check for `async {` and `async move {`,
// or `async gen {` and `async gen move {`.
this.parse_gen_block()
} else {
this.parse_expr_closure()
@ -1451,7 +1452,7 @@ impl<'a> Parser<'a> {
} else if this.eat_keyword(kw::Await) {
this.recover_incorrect_await_syntax(lo, this.prev_token.span)
} else if this.token.uninterpolated_span().at_least_rust_2024() {
if this.is_gen_block(kw::Gen) {
if this.is_gen_block(kw::Gen, 0) {
this.parse_gen_block()
} else {
this.parse_expr_lit()
@ -3179,7 +3180,7 @@ impl<'a> Parser<'a> {
fn parse_gen_block(&mut self) -> PResult<'a, P<Expr>> {
let lo = self.token.span;
let kind = if self.eat_keyword(kw::Async) {
GenBlockKind::Async
if self.eat_keyword(kw::Gen) { GenBlockKind::AsyncGen } else { GenBlockKind::Async }
} else {
assert!(self.eat_keyword(kw::Gen));
self.sess.gated_spans.gate(sym::gen_blocks, lo.to(self.token.span));
@ -3191,22 +3192,26 @@ impl<'a> Parser<'a> {
Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
}
fn is_gen_block(&self, kw: Symbol) -> bool {
self.token.is_keyword(kw)
fn is_gen_block(&self, kw: Symbol, lookahead: usize) -> bool {
self.is_keyword_ahead(lookahead, &[kw])
&& ((
// `async move {`
self.is_keyword_ahead(1, &[kw::Move])
&& self.look_ahead(2, |t| {
self.is_keyword_ahead(lookahead + 1, &[kw::Move])
&& self.look_ahead(lookahead + 2, |t| {
*t == token::OpenDelim(Delimiter::Brace) || t.is_whole_block()
})
) || (
// `async {`
self.look_ahead(1, |t| {
self.look_ahead(lookahead + 1, |t| {
*t == token::OpenDelim(Delimiter::Brace) || t.is_whole_block()
})
))
}
pub(super) fn is_async_gen_block(&self) -> bool {
self.token.is_keyword(kw::Async) && self.is_gen_block(kw::Gen, 1)
}
fn is_certainly_not_a_block(&self) -> bool {
self.look_ahead(1, |t| t.is_ident())
&& (

6
compiler/rustc_parse/src/parser/item.rs
View File

@ -2359,8 +2359,10 @@ impl<'a> Parser<'a> {
|| case == Case::Insensitive
&& t.is_non_raw_ident_where(|i| quals.iter().any(|qual| qual.as_str() == i.name.as_str().to_lowercase()))
)
// Rule out unsafe extern block.
&& !self.is_unsafe_foreign_mod())
// Rule out `unsafe extern {`.
&& !self.is_unsafe_foreign_mod()
// Rule out `async gen {` and `async gen move {`
&& !self.is_async_gen_block())
})
// `extern ABI fn`
|| self.check_keyword_case(kw::Extern, case)

1
compiler/rustc_smir/src/rustc_smir/convert/mod.rs
View File

@ -56,6 +56,7 @@ impl<'tcx> Stable<'tcx> for rustc_hir::CoroutineKind {
stable_mir::mir::CoroutineKind::Gen(source.stable(tables))
}
CoroutineKind::Coroutine => stable_mir::mir::CoroutineKind::Coroutine,
CoroutineKind::AsyncGen(_) => todo!(),
}
}
}

5
compiler/rustc_span/src/symbol.rs
View File

@ -139,6 +139,9 @@ symbols! {
AssertParamIsClone,
AssertParamIsCopy,
AssertParamIsEq,
AsyncGenFinished,
AsyncGenPending,
AsyncGenReady,
AtomicBool,
AtomicI128,
AtomicI16,
@ -423,6 +426,7 @@ symbols! {
async_closure,
async_fn_in_trait,
async_fn_track_caller,
async_iterator,
atomic,
atomic_mod,
atomics,
@ -1200,6 +1204,7 @@ symbols! {
pointer,
pointer_like,
poll,
poll_next,
post_dash_lto: "post-lto",
powerpc_target_feature,
powf32,

7
compiler/rustc_trait_selection/src/solve/assembly/mod.rs
View File

@ -207,6 +207,11 @@ pub(super) trait GoalKind<'tcx>:
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
fn consider_builtin_async_iterator_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
/// A coroutine (that doesn't come from an `async` or `gen` desugaring) is known to
/// implement `Coroutine<R, Yield = Y, Return = O>`, given the resume, yield,
/// and return types of the coroutine computed during type-checking.
@ -565,6 +570,8 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
G::consider_builtin_future_candidate(self, goal)
} else if lang_items.iterator_trait() == Some(trait_def_id) {
G::consider_builtin_iterator_candidate(self, goal)
} else if lang_items.async_iterator_trait() == Some(trait_def_id) {
G::consider_builtin_async_iterator_candidate(self, goal)
} else if lang_items.coroutine_trait() == Some(trait_def_id) {
G::consider_builtin_coroutine_candidate(self, goal)
} else if lang_items.discriminant_kind_trait() == Some(trait_def_id) {

34
compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
View File

@ -510,6 +510,40 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
)
}
fn consider_builtin_async_iterator_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx> {
let self_ty = goal.predicate.self_ty();
let ty::Coroutine(def_id, args, _) = *self_ty.kind() else {
return Err(NoSolution);
};
// Coroutines are not AsyncIterators unless they come from `gen` desugaring
let tcx = ecx.tcx();
if !tcx.coroutine_is_async_gen(def_id) {
return Err(NoSolution);
}
ecx.probe_misc_candidate("builtin AsyncIterator kind").enter(|ecx| {
// Take `AsyncIterator<Item = I>` and turn it into the corresponding
// coroutine yield ty `Poll<Option<I>>`.
let expected_ty = Ty::new_adt(
tcx,
tcx.adt_def(tcx.require_lang_item(LangItem::Poll, None)),
tcx.mk_args(&[Ty::new_adt(
tcx,
tcx.adt_def(tcx.require_lang_item(LangItem::Option, None)),
tcx.mk_args(&[goal.predicate.term.into()]),
)
.into()]),
);
let yield_ty = args.as_coroutine().yield_ty();
ecx.eq(goal.param_env, expected_ty, yield_ty)?;
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn consider_builtin_coroutine_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,

24
compiler/rustc_trait_selection/src/solve/trait_goals.rs
View File

@ -370,6 +370,30 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
fn consider_builtin_async_iterator_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx> {
if goal.predicate.polarity != ty::ImplPolarity::Positive {
return Err(NoSolution);
}
let ty::Coroutine(def_id, _, _) = *goal.predicate.self_ty().kind() else {
return Err(NoSolution);
};
// Coroutines are not iterators unless they come from `gen` desugaring
let tcx = ecx.tcx();
if !tcx.coroutine_is_async_gen(def_id) {
return Err(NoSolution);
}
// Gen coroutines unconditionally implement `Iterator`
// Technically, we need to check that the iterator output type is Sized,
// but that's already proven by the coroutines being WF.
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
fn consider_builtin_coroutine_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,

21
compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
View File

@ -2587,6 +2587,23 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
CoroutineKind::Async(CoroutineSource::Closure) => {
format!("future created by async closure is not {trait_name}")
}
CoroutineKind::AsyncGen(CoroutineSource::Fn) => self
.tcx
.parent(coroutine_did)
.as_local()
.map(|parent_did| self.tcx.local_def_id_to_hir_id(parent_did))
.and_then(|parent_hir_id| hir.opt_name(parent_hir_id))
.map(|name| {
format!("async iterator returned by `{name}` is not {trait_name}")
})?,
CoroutineKind::AsyncGen(CoroutineSource::Block) => {
format!("async iterator created by async gen block is not {trait_name}")
}
CoroutineKind::AsyncGen(CoroutineSource::Closure) => {
format!(
"async iterator created by async gen closure is not {trait_name}"
)
}
CoroutineKind::Gen(CoroutineSource::Fn) => self
.tcx
.parent(coroutine_did)
@ -3127,7 +3144,9 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
let what = match self.tcx.coroutine_kind(coroutine_def_id) {
None
| Some(hir::CoroutineKind::Coroutine)
| Some(hir::CoroutineKind::Gen(_)) => "yield",
| Some(hir::CoroutineKind::Gen(_))
// FIXME(gen_blocks): This could be yield or await...
| Some(hir::CoroutineKind::AsyncGen(_)) => "yield",
Some(hir::CoroutineKind::Async(..)) => "await",
};
err.note(format!(

3
compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
View File

@ -1921,6 +1921,9 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
hir::CoroutineKind::Async(hir::CoroutineSource::Block) => "an async block",
hir::CoroutineKind::Async(hir::CoroutineSource::Fn) => "an async function",
hir::CoroutineKind::Async(hir::CoroutineSource::Closure) => "an async closure",
hir::CoroutineKind::AsyncGen(hir::CoroutineSource::Block) => "an async gen block",
hir::CoroutineKind::AsyncGen(hir::CoroutineSource::Fn) => "an async gen function",
hir::CoroutineKind::AsyncGen(hir::CoroutineSource::Closure) => "an async gen closure",
hir::CoroutineKind::Gen(hir::CoroutineSource::Block) => "a gen block",
hir::CoroutineKind::Gen(hir::CoroutineSource::Fn) => "a gen function",
hir::CoroutineKind::Gen(hir::CoroutineSource::Closure) => "a gen closure",

66
compiler/rustc_trait_selection/src/traits/project.rs
View File

@ -1823,11 +1823,18 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
let self_ty = selcx.infcx.shallow_resolve(obligation.predicate.self_ty());
let lang_items = selcx.tcx().lang_items();
if [lang_items.coroutine_trait(), lang_items.future_trait(), lang_items.iterator_trait()].contains(&Some(trait_ref.def_id))
|| selcx.tcx().fn_trait_kind_from_def_id(trait_ref.def_id).is_some()
if [
lang_items.coroutine_trait(),
lang_items.future_trait(),
lang_items.iterator_trait(),
lang_items.async_iterator_trait(),
lang_items.fn_trait(),
lang_items.fn_mut_trait(),
lang_items.fn_once_trait(),
].contains(&Some(trait_ref.def_id))
{
true
} else if lang_items.discriminant_kind_trait() == Some(trait_ref.def_id) {
}else if lang_items.discriminant_kind_trait() == Some(trait_ref.def_id) {
match self_ty.kind() {
ty::Bool
| ty::Char
@ -2042,6 +2049,8 @@ fn confirm_select_candidate<'cx, 'tcx>(
confirm_future_candidate(selcx, obligation, data)
} else if lang_items.iterator_trait() == Some(trait_def_id) {
confirm_iterator_candidate(selcx, obligation, data)
} else if lang_items.async_iterator_trait() == Some(trait_def_id) {
confirm_async_iterator_candidate(selcx, obligation, data)
} else if selcx.tcx().fn_trait_kind_from_def_id(trait_def_id).is_some() {
if obligation.predicate.self_ty().is_closure() {
confirm_closure_candidate(selcx, obligation, data)
@ -2203,6 +2212,57 @@ fn confirm_iterator_candidate<'cx, 'tcx>(
.with_addl_obligations(obligations)
}
fn confirm_async_iterator_candidate<'cx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,
nested: Vec<PredicateObligation<'tcx>>,
) -> Progress<'tcx> {
let ty::Coroutine(_, args, _) =
selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
else {
unreachable!()
};
let gen_sig = args.as_coroutine().sig();
let Normalized { value: gen_sig, obligations } = normalize_with_depth(
selcx,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
gen_sig,
);
debug!(?obligation, ?gen_sig, ?obligations, "confirm_async_iterator_candidate");
let tcx = selcx.tcx();
let iter_def_id = tcx.require_lang_item(LangItem::AsyncIterator, None);
let (trait_ref, yield_ty) = super::util::async_iterator_trait_ref_and_outputs(
tcx,
iter_def_id,
obligation.predicate.self_ty(),
gen_sig,
);
debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Item);
let ty::Adt(_poll_adt, args) = *yield_ty.kind() else {
bug!();
};
let ty::Adt(_option_adt, args) = *args.type_at(0).kind() else {
bug!();
};
let item_ty = args.type_at(0);
let predicate = ty::ProjectionPredicate {
projection_ty: ty::AliasTy::new(tcx, obligation.predicate.def_id, trait_ref.args),
term: item_ty.into(),
};
confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false)
.with_addl_obligations(nested)
.with_addl_obligations(obligations)
}
fn confirm_builtin_candidate<'cx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,

30
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
View File

@ -112,6 +112,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
self.assemble_future_candidates(obligation, &mut candidates);
} else if lang_items.iterator_trait() == Some(def_id) {
self.assemble_iterator_candidates(obligation, &mut candidates);
} else if lang_items.async_iterator_trait() == Some(def_id) {
self.assemble_async_iterator_candidates(obligation, &mut candidates);
}
self.assemble_closure_candidates(obligation, &mut candidates);
@ -258,6 +260,34 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
}
fn assemble_async_iterator_candidates(
&mut self,
obligation: &PolyTraitObligation<'tcx>,
candidates: &mut SelectionCandidateSet<'tcx>,
) {
let self_ty = obligation.self_ty().skip_binder();
if let ty::Coroutine(did, args, _) = *self_ty.kind() {
// gen constructs get lowered to a special kind of coroutine that
// should directly `impl AsyncIterator`.
if self.tcx().coroutine_is_async_gen(did) {
debug!(?self_ty, ?obligation, "assemble_iterator_candidates",);
// Can only confirm this candidate if we have constrained
// the `Yield` type to at least `Poll<Option<?0>>`..
let ty::Adt(_poll_def, args) = *args.as_coroutine().yield_ty().kind() else {
candidates.ambiguous = true;
return;
};
let ty::Adt(_option_def, _) = *args.type_at(0).kind() else {
candidates.ambiguous = true;
return;
};
candidates.vec.push(AsyncIteratorCandidate);
}
}
}
/// Checks for the artificial impl that the compiler will create for an obligation like `X :
/// FnMut<..>` where `X` is a closure type.
///

34
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View File

@ -98,6 +98,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplSource::Builtin(BuiltinImplSource::Misc, vtable_iterator)
}
AsyncIteratorCandidate => {
let vtable_iterator = self.confirm_async_iterator_candidate(obligation)?;
ImplSource::Builtin(BuiltinImplSource::Misc, vtable_iterator)
}
FnPointerCandidate { is_const } => {
let data = self.confirm_fn_pointer_candidate(obligation, is_const)?;
ImplSource::Builtin(BuiltinImplSource::Misc, data)
@ -813,6 +818,35 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
Ok(nested)
}
fn confirm_async_iterator_candidate(
&mut self,
obligation: &PolyTraitObligation<'tcx>,
) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
// Okay to skip binder because the args on coroutine types never
// touch bound regions, they just capture the in-scope
// type/region parameters.
let self_ty = self.infcx.shallow_resolve(obligation.self_ty().skip_binder());
let ty::Coroutine(coroutine_def_id, args, _) = *self_ty.kind() else {
bug!("closure candidate for non-closure {:?}", obligation);
};
debug!(?obligation, ?coroutine_def_id, ?args, "confirm_async_iterator_candidate");
let gen_sig = args.as_coroutine().sig();
let (trait_ref, _) = super::util::async_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,
);
let nested = self.confirm_poly_trait_refs(obligation, ty::Binder::dummy(trait_ref))?;
debug!(?trait_ref, ?nested, "iterator candidate obligations");
Ok(nested)
}
#[instrument(skip(self), level = "debug")]
fn confirm_closure_candidate(
&mut self,

6
compiler/rustc_trait_selection/src/traits/select/mod.rs
View File

@ -1875,6 +1875,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
| CoroutineCandidate
| FutureCandidate
| IteratorCandidate
| AsyncIteratorCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
@ -1904,6 +1905,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
| CoroutineCandidate
| FutureCandidate
| IteratorCandidate
| AsyncIteratorCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
@ -1939,6 +1941,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
| CoroutineCandidate
| FutureCandidate
| IteratorCandidate
| AsyncIteratorCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
@ -1954,6 +1957,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
| CoroutineCandidate
| FutureCandidate
| IteratorCandidate
| AsyncIteratorCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
@ -2061,6 +2065,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
| CoroutineCandidate
| FutureCandidate
| IteratorCandidate
| AsyncIteratorCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
@ -2072,6 +2077,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
| CoroutineCandidate
| FutureCandidate
| IteratorCandidate
| AsyncIteratorCandidate
| FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate

11
compiler/rustc_trait_selection/src/traits/util.rs
View File

@ -308,6 +308,17 @@ pub fn iterator_trait_ref_and_outputs<'tcx>(
(trait_ref, sig.yield_ty)
}
pub fn async_iterator_trait_ref_and_outputs<'tcx>(
tcx: TyCtxt<'tcx>,
async_iterator_def_id: DefId,
self_ty: 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, async_iterator_def_id, [self_ty]);
(trait_ref, sig.yield_ty)
}
pub fn impl_item_is_final(tcx: TyCtxt<'_>, assoc_item: &ty::AssocItem) -> bool {
assoc_item.defaultness(tcx).is_final()
&& tcx.defaultness(assoc_item.container_id(tcx)).is_final()

30
compiler/rustc_ty_utils/src/abi.rs
View File

@ -119,9 +119,9 @@ fn fn_sig_for_fn_abi<'tcx>(
// unlike for all other coroutine kinds.
env_ty
}
hir::CoroutineKind::Async(_) | hir::CoroutineKind::Coroutine => {
Ty::new_adt(tcx, pin_adt_ref, pin_args)
}
hir::CoroutineKind::Async(_)
| hir::CoroutineKind::AsyncGen(_)
| hir::CoroutineKind::Coroutine => Ty::new_adt(tcx, pin_adt_ref, pin_args),
};
// The `FnSig` and the `ret_ty` here is for a coroutines main
@ -168,6 +168,30 @@ fn fn_sig_for_fn_abi<'tcx>(
(None, ret_ty)
}
hir::CoroutineKind::AsyncGen(_) => {
// The signature should be
// `AsyncIterator::poll_next(_, &mut Context<'_>) -> Poll<Option<Output>>`
assert_eq!(sig.return_ty, tcx.types.unit);
// Yield type is already `Poll<Option<yield_ty>>`
let ret_ty = sig.yield_ty;
// We have to replace the `ResumeTy` that is used for type and borrow checking
// with `&mut Context<'_>` which is used in codegen.
#[cfg(debug_assertions)]
{
if let ty::Adt(resume_ty_adt, _) = sig.resume_ty.kind() {
let expected_adt =
tcx.adt_def(tcx.require_lang_item(LangItem::ResumeTy, None));
assert_eq!(*resume_ty_adt, expected_adt);
} else {
panic!("expected `ResumeTy`, found `{:?}`", sig.resume_ty);
};
}
let context_mut_ref = Ty::new_task_context(tcx);
(Some(context_mut_ref), ret_ty)
}
hir::CoroutineKind::Coroutine => {
// The signature should be `Coroutine::resume(_, Resume) -> CoroutineState<Yield, Return>`
let state_did = tcx.require_lang_item(LangItem::CoroutineState, None);

15
compiler/rustc_ty_utils/src/instance.rs
View File

@ -271,6 +271,21 @@ fn resolve_associated_item<'tcx>(
debug_assert!(tcx.defaultness(trait_item_id).has_value());
Some(Instance::new(trait_item_id, rcvr_args))
}
} else if Some(trait_ref.def_id) == lang_items.async_iterator_trait() {
let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else {
bug!()
};
if cfg!(debug_assertions) && tcx.item_name(trait_item_id) != sym::poll_next {
span_bug!(
tcx.def_span(coroutine_def_id),
"no definition for `{trait_ref}::{}` for built-in coroutine type",
tcx.item_name(trait_item_id)
)
}
// `AsyncIterator::poll_next` is generated by the compiler.
Some(Instance { def: ty::InstanceDef::Item(coroutine_def_id), args })
} else if Some(trait_ref.def_id) == lang_items.coroutine_trait() {
let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else {
bug!()

25
library/core/src/async_iter/async_iter.rs
View File

@ -13,6 +13,7 @@ use crate::task::{Context, Poll};
#[unstable(feature = "async_iterator", issue = "79024")]
#[must_use = "async iterators do nothing unless polled"]
#[doc(alias = "Stream")]
#[cfg_attr(not(bootstrap), lang = "async_iterator")]
pub trait AsyncIterator {
/// The type of items yielded by the async iterator.
type Item;
@ -109,3 +110,27 @@ where
(**self).size_hint()
}
}
#[unstable(feature = "async_gen_internals", issue = "none")]
impl<T> Poll<Option<T>> {
/// A helper function for internal desugaring -- produces `Ready(Some(t))`,
/// which corresponds to the async iterator yielding a value.
#[unstable(feature = "async_gen_internals", issue = "none")]
#[cfg_attr(not(bootstrap), lang = "AsyncGenReady")]
pub fn async_gen_ready(t: T) -> Self {
Poll::Ready(Some(t))
}
/// A helper constant for internal desugaring -- produces `Pending`,
/// which corresponds to the async iterator pending on an `.await`.
#[unstable(feature = "async_gen_internals", issue = "none")]
#[cfg_attr(not(bootstrap), lang = "AsyncGenPending")]
// FIXME(gen_blocks): This probably could be deduplicated.
pub const PENDING: Self = Poll::Pending;
/// A helper constant for internal desugaring -- produces `Ready(None)`,
/// which corresponds to the async iterator finishing its iteration.
#[unstable(feature = "async_gen_internals", issue = "none")]
#[cfg_attr(not(bootstrap), lang = "AsyncGenFinished")]
pub const FINISHED: Self = Poll::Ready(None);
}