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typeck: silence unreachable code from await
This commit silences the unreachable code lint when it originates from
within a await desugaring.

Signed-off-by: David Wood <david@davidtw.co>
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davidtwco committed Sep 30, 2019
1 parent 22bc9e1 commit 870b47f
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Showing 4 changed files with 43 additions and 1 deletion.
3 changes: 2 additions & 1 deletion src/librustc_typeck/check/mod.rs
Expand Up @@ -2364,7 +2364,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// which diverges, that we are about to lint on. This gives suboptimal diagnostics.
// Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
if !span.is_desugaring(DesugaringKind::CondTemporary) &&
!span.is_desugaring(DesugaringKind::Async)
!span.is_desugaring(DesugaringKind::Async) &&
!orig_span.is_desugaring(DesugaringKind::Await)
{
self.diverges.set(Diverges::WarnedAlways);

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12 changes: 12 additions & 0 deletions src/test/ui/async-await/unreachable-lint-1.rs
@@ -0,0 +1,12 @@
// edition:2018
#![deny(unreachable_code)]

async fn foo() {
return; bar().await;
//~^ ERROR unreachable statement
}

async fn bar() {
}

fn main() { }
16 changes: 16 additions & 0 deletions src/test/ui/async-await/unreachable-lint-1.stderr
@@ -0,0 +1,16 @@
error: unreachable statement
--> $DIR/unreachable-lint-1.rs:5:13
|
LL | return; bar().await;
| ------ ^^^^^^^^^^^^ unreachable statement
| |
| any code following this expression is unreachable
|
note: lint level defined here
--> $DIR/unreachable-lint-1.rs:2:9
|
LL | #![deny(unreachable_code)]
| ^^^^^^^^^^^^^^^^

error: aborting due to previous error

13 changes: 13 additions & 0 deletions src/test/ui/async-await/unreachable-lint.rs
@@ -0,0 +1,13 @@
// check-pass
// edition:2018
#![deny(unreachable_code)]

async fn foo() {
endless().await;
}

async fn endless() -> ! {
loop {}
}

fn main() { }

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