bjoernager/rust
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Remove identity_future indirection

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This was previously needed because the indirection used to hide some unexplained lifetime errors, which it turned out were related to the `min_choice` algorithm.

Removing the indirection also solves a couple of cycle errors, large moves and makes async blocks support the `#[track_caller]` annotation.
This commit is contained in:
Arpad Borsos 2022-11-24 17:58:32 +01:00 • committed by Arpad Borsos
parent 64165aac68
commit 9f03cfc207
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GPG key ID: 570F20163159CB55
32 changed files with 149 additions and 361 deletions
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64
compiler/rustc_ast_lowering/src/expr.rs
View file

@ -32,7 +32,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
pub(super) fn lower_expr_mut(&mut self, e: &Expr) -> hir::Expr<'hir> {
ensure_sufficient_stack(|| {
match &e.kind {
// Paranthesis expression does not have a HirId and is handled specially.
// Parenthesis expression does not have a HirId and is handled specially.
ExprKind::Paren(ex) => {
let mut ex = self.lower_expr_mut(ex);
// Include parens in span, but only if it is a super-span.
@ -63,6 +63,20 @@ impl<'hir> LoweringContext<'_, 'hir> {
ExprKind::ForLoop(pat, head, body, opt_label) => {
return self.lower_expr_for(e, pat, head, body, *opt_label);
}
// Similarly, async blocks do not use `e.id` but rather `closure_node_id`.
ExprKind::Async(capture_clause, closure_node_id, block) => {
let hir_id = self.lower_node_id(*closure_node_id);
self.lower_attrs(hir_id, &e.attrs);
return self.make_async_expr(
*capture_clause,
hir_id,
*closure_node_id,
None,
e.span,
hir::AsyncGeneratorKind::Block,
|this| this.with_new_scopes(|this| this.lower_block_expr(block)),
);
}
_ => (),
}
@ -182,15 +196,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.arena.alloc_from_iter(arms.iter().map(|x| self.lower_arm(x))),
hir::MatchSource::Normal,
),
ExprKind::Async(capture_clause, closure_node_id, block) => self.make_async_expr(
*capture_clause,
hir_id,
*closure_node_id,
None,
e.span,
hir::AsyncGeneratorKind::Block,
|this| this.with_new_scopes(|this| this.lower_block_expr(block)),
),
ExprKind::Await(expr) => {
let dot_await_span = if expr.span.hi() < e.span.hi() {
let span_with_whitespace = self
@ -324,7 +329,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
),
ExprKind::Try(sub_expr) => self.lower_expr_try(e.span, sub_expr),
ExprKind::Paren(_) | ExprKind::ForLoop(..) => unreachable!("already handled"),
ExprKind::Paren(_) | ExprKind::ForLoop(..) | ExprKind::Async(..) => {
unreachable!("already handled")
}
ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span),
};
@ -586,9 +593,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
/// This results in:
///
/// ```text
/// std::future::identity_future(static move? |_task_context| -> <ret_ty> {
/// static move? |_task_context| -> <ret_ty> {
/// <body>
/// })
/// }
/// ```
pub(super) fn make_async_expr(
&mut self,
@ -599,7 +606,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
span: Span,
async_gen_kind: hir::AsyncGeneratorKind,
body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
) -> hir::ExprKind<'hir> {
) -> hir::Expr<'hir> {
let output = ret_ty.unwrap_or_else(|| hir::FnRetTy::DefaultReturn(self.lower_span(span)));
// Resume argument type: `ResumeTy`
@ -664,13 +671,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
};
let hir_id = self.lower_node_id(closure_node_id);
let unstable_span =
self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
if self.tcx.features().closure_track_caller
&& let Some(attrs) = self.attrs.get(&outer_hir_id.local_id)
&& attrs.into_iter().any(|attr| attr.has_name(sym::track_caller))
{
let unstable_span =
self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
self.lower_attrs(
hir_id,
&[Attribute {
@ -689,22 +695,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
);
}
let generator = hir::Expr { hir_id, kind: generator_kind, span: self.lower_span(span) };
// FIXME(swatinem):
// For some reason, the async block needs to flow through *any*
// call (like the identity function), as otherwise type and lifetime
// inference have a hard time figuring things out.
// Without this, we would get:
// E0720 in tests/ui/impl-trait/in-trait/default-body-with-rpit.rs
// E0700 in tests/ui/self/self_lifetime-async.rs
// `future::identity_future`:
let identity_future =
self.expr_lang_item_path(unstable_span, hir::LangItem::IdentityFuture, None);
// `future::identity_future(generator)`:
hir::ExprKind::Call(self.arena.alloc(identity_future), arena_vec![self; generator])
hir::Expr { hir_id, kind: generator_kind, span: self.lower_span(span) }
}
/// Desugar `<expr>.await` into:
@ -1010,7 +1001,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
// Transform `async |x: u8| -> X { ... }` into
// `|x: u8| identity_future(|| -> X { ... })`.
// `|x: u8| || -> X { ... }`.
let body_id = this.lower_fn_body(&outer_decl, |this| {
let async_ret_ty = if let FnRetTy::Ty(ty) = &decl.output {
let itctx = ImplTraitContext::Disallowed(ImplTraitPosition::AsyncBlock);
@ -1019,7 +1010,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
None
};
let async_body = this.make_async_expr(
this.make_async_expr(
capture_clause,
closure_hir_id,
inner_closure_id,
@ -1027,8 +1018,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
body.span,
hir::AsyncGeneratorKind::Closure,
|this| this.with_new_scopes(|this| this.lower_expr_mut(body)),
);
this.expr(fn_decl_span, async_body)
)
});
body_id
});

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

@ -1180,7 +1180,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
},
);
(this.arena.alloc_from_iter(parameters), this.expr(body.span, async_expr))
(this.arena.alloc_from_iter(parameters), async_expr)
})
}