async fn: 'static lifetime not inferred for Arc trait object #54974
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A-async-await
Area: Async & Await
A-lifetimes
Area: Lifetimes / regions
AsyncAwait-Polish
Async-await issues that are part of the "polish" area
C-bug
Category: This is a bug.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
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jonas-schievink
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A-lifetimes
nikomatsakis
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AsyncAwait-Polish
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Tagging as blocking -- this issue ought to be resolved before async-await can be stabilized, because it is generally surprising and kind of a bug. However, we expect it to get fixed by fixing #56238 (see that issue for notes as to why). |
bors
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that referenced
this issue
Apr 2, 2019
Refactor async fn return type lowering
async fn now lowers directly to an existential type declaration
rather than reusing the `impl Trait` return type lowering.
As part of this, it lowers all argument-position elided lifetimes
using the in-band-lifetimes machinery, creating fresh parameter
names for each of them, using each lifetime parameter as a generic
argument to the generated existential type.
This doesn't currently successfully allow multiple
argument-position elided lifetimes since `existential type`
doesn't yet support multiple lifetimes where neither outlive
the other:
```rust
existential type Foo<'a, 'b>:; // error: ambiguous lifetime bound in `impl Trait`
fn foo<'a, 'b>(_: &'a u8, _: &'b u8) -> Foo<'a, 'b> { () }
```
This requires a separate fix.
Fix #59001
Fix #58885
Fix #55324
Fix #54974
Progress on #56238
r? @nikomatsakis
Centril
added a commit
to Centril/rust
that referenced
this issue
Apr 2, 2019
Refactor async fn return type lowering
async fn now lowers directly to an existential type declaration
rather than reusing the `impl Trait` return type lowering.
As part of this, it lowers all argument-position elided lifetimes
using the in-band-lifetimes machinery, creating fresh parameter
names for each of them, using each lifetime parameter as a generic
argument to the generated existential type.
This doesn't currently successfully allow multiple
argument-position elided lifetimes since `existential type`
doesn't yet support multiple lifetimes where neither outlive
the other:
```rust
existential type Foo<'a, 'b>:; // error: ambiguous lifetime bound in `impl Trait`
fn foo<'a, 'b>(_: &'a u8, _: &'b u8) -> Foo<'a, 'b> { () }
```
This requires a separate fix.
Fix rust-lang#59001
Fix rust-lang#58885
Fix rust-lang#55324
Fix rust-lang#54974
Progress on rust-lang#56238
r? @nikomatsakis
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Playground link to reproduce: https://play.rust-lang.org/?gist=697ecc0c55cbf30bee0fb2d87736f704&version=nightly&mode=debug&edition=2018
Changing the suggested type to
Arc<SomeTrait + 'static>fixes the compiler error.Having to manually specify this does not seem intentional. Perhaps this
'staticlifetime should be automatically inferred?The text was updated successfully, but these errors were encountered: