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Rollup merge of #64292 - davidtwco:issue-63832-await-temporary-lifetimes, r=matthewjasper

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lowering: extend temporary lifetimes around await

Fixes #63832.

r? @matthewjasper
cc @nikomatsakis
This commit is contained in:
Mazdak Farrokhzad 2019-09-10 17:19:25 +02:00 • committed by GitHub
commit a1755dfbc7
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4 changed files with 58 additions and 32 deletions
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35
src/librustc/hir/lowering/expr.rs
View file

@ -507,14 +507,13 @@ impl LoweringContext<'_> {
/// Desugar `<expr>.await` into:
/// ```rust
/// {
/// let mut pinned = <expr>;
/// loop {
/// match <expr> {
/// mut pinned => loop {
/// match ::std::future::poll_with_tls_context(unsafe {
/// ::std::pin::Pin::new_unchecked(&mut pinned)
/// <::std::pin::Pin>::new_unchecked(&mut pinned)
/// }) {
/// ::std::task::Poll::Ready(result) => break result,
/// ::std::task::Poll::Pending => {},
/// ::std::task::Poll::Pending => {}
/// }
/// yield ();
/// }
@ -549,21 +548,12 @@ impl LoweringContext<'_> {
self.allow_gen_future.clone(),
);
// let mut pinned = <expr>;
let expr = P(self.lower_expr(expr));
let pinned_ident = Ident::with_dummy_span(sym::pinned);
let (pinned_pat, pinned_pat_hid) = self.pat_ident_binding_mode(
span,
pinned_ident,
hir::BindingAnnotation::Mutable,
);
let pinned_let = self.stmt_let_pat(
ThinVec::new(),
span,
Some(expr),
pinned_pat,
hir::LocalSource::AwaitDesugar,
);
// ::std::future::poll_with_tls_context(unsafe {
// ::std::pin::Pin::new_unchecked(&mut pinned)
@ -621,7 +611,7 @@ impl LoweringContext<'_> {
self.arm(hir_vec![pending_pat], empty_block)
};
let match_stmt = {
let inner_match_stmt = {
let match_expr = self.expr_match(
span,
poll_expr,
@ -643,10 +633,11 @@ impl LoweringContext<'_> {
let loop_block = P(self.block_all(
span,
hir_vec![match_stmt, yield_stmt],
hir_vec![inner_match_stmt, yield_stmt],
None,
));
// loop { .. }
let loop_expr = P(hir::Expr {
hir_id: loop_hir_id,
node: hir::ExprKind::Loop(
@ -658,10 +649,14 @@ impl LoweringContext<'_> {
attrs: ThinVec::new(),
});
hir::ExprKind::Block(
P(self.block_all(span, hir_vec![pinned_let], Some(loop_expr))),
None,
)
// mut pinned => loop { ... }
let pinned_arm = self.arm(hir_vec![pinned_pat], loop_expr);
// match <expr> {
// mut pinned => loop { .. }
// }
let expr = P(self.lower_expr(expr));
hir::ExprKind::Match(expr, hir_vec![pinned_arm], hir::MatchSource::AwaitDesugar)
}
fn lower_expr_closure(