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Reintroduce into_future in .await desugaring

Browse source 
This is a reintroduction of the remaining parts from
https://github.com/rust-lang/rust/pull/65244 that have not been relanded
yet.

Issues GH-67644, GH-67982
This commit is contained in:
Eric Holk 2021-11-09 10:08:38 -08:00
parent 936f2600b6
commit dfa0db5961
9 changed files with 91 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

26
compiler/rustc_ast_lowering/src/expr.rs
View file

@ -593,7 +593,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
/// Desugar `<expr>.await` into:
/// ```rust
/// match <expr> {
/// match ::std::future::IntoFuture::into_future(<expr>) {
/// mut pinned => loop {
/// match unsafe { ::std::future::Future::poll(
/// <::std::pin::Pin>::new_unchecked(&mut pinned),
@ -629,7 +629,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
await_span,
self.allow_gen_future.clone(),
);
let expr = self.lower_expr(expr);
let expr = self.lower_expr_mut(expr);
let pinned_ident = Ident::with_dummy_span(sym::pinned);
let (pinned_pat, pinned_pat_hid) =
@ -746,10 +746,26 @@ impl<'hir> LoweringContext<'_, 'hir> {
// mut pinned => loop { ... }
let pinned_arm = self.arm(pinned_pat, loop_expr);
// match <expr> {
// mut pinned => loop { .. }
// `match ::std::future::IntoFuture::into_future(<expr>) { ... }`
let into_future_span = self.mark_span_with_reason(
DesugaringKind::Await,
await_span,
self.allow_into_future.clone(),
);
//let expr = self.lower_expr_mut(expr);
let into_future_expr = self.expr_call_lang_item_fn(
into_future_span,
hir::LangItem::IntoFutureIntoFuture,
arena_vec![self; expr],
);
// match <into_future_expr> { // mut pinned => loop { .. }
// }
hir::ExprKind::Match(expr, arena_vec![self; pinned_arm], hir::MatchSource::AwaitDesugar)
hir::ExprKind::Match(
into_future_expr,
arena_vec![self; pinned_arm],
hir::MatchSource::AwaitDesugar,
)
}
fn lower_expr_closure(

2
compiler/rustc_ast_lowering/src/lib.rs
View file

@ -162,6 +162,7 @@ struct LoweringContext<'a, 'hir: 'a> {
allow_try_trait: Option<Lrc<[Symbol]>>,
allow_gen_future: Option<Lrc<[Symbol]>>,
allow_into_future: Option<Lrc<[Symbol]>>,
}
pub trait ResolverAstLowering {
@ -320,6 +321,7 @@ pub fn lower_crate<'a, 'hir>(
in_scope_lifetimes: Vec::new(),
allow_try_trait: Some([sym::try_trait_v2][..].into()),
allow_gen_future: Some([sym::gen_future][..].into()),
allow_into_future: Some([sym::into_future][..].into()),
}
.lower_crate(krate)
}

1
compiler/rustc_hir/src/lang_items.rs
View file

@ -347,6 +347,7 @@ language_item_table! {
ControlFlowContinue, sym::Continue, cf_continue_variant, Target::Variant, GenericRequirement::None;
ControlFlowBreak, sym::Break, cf_break_variant, Target::Variant, GenericRequirement::None;
IntoFutureIntoFuture, sym::into_future, into_future_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
IntoIterIntoIter, sym::into_iter, into_iter_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
IteratorNext, sym::next, next_fn, Target::Method(MethodKind::Trait { body: false}), GenericRequirement::None;

2
compiler/rustc_span/src/symbol.rs
View file

@ -196,6 +196,7 @@ symbols! {
Implied,
Input,
Into,
IntoFuture,
IntoIterator,
IoRead,
IoWrite,
@ -734,6 +735,7 @@ symbols! {
inout,
instruction_set,
intel,
into_future,
into_iter,
intra_doc_pointers,
intrinsics,