1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
|
#![feature(type_alias_impl_trait)]
use std::fmt::Debug;
type Foo = impl Debug;
fn is_send<T: Send>() {}
fn not_good() {
// Error: this function does not constrain `Foo` to any particular
// hidden type, so it cannot rely on `Send` being true.
is_send::<Foo>();
//~^ ERROR: cannot check whether the hidden type of `reveal_local[9507]::Foo::{opaque#0}` satisfies auto traits
}
fn not_gooder() -> Foo {
// Constrain `Foo = u32`
let x: Foo = 22_u32;
// while we could know this from the hidden type, it would
// need extra roundabout logic to support it.
is_send::<Foo>();
//~^ ERROR: type annotations needed: cannot satisfy `Foo: Send`
x
}
fn main() {}
|
