src/test/ui/never_type/never-value-fallback-issue-66757.rs


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
29
30
31

// Regression test for #66757
//
// Test than when you have a `!` value (e.g., the local variable
// never) and an uninferred variable (here the argument to `From`) it
// doesn't fallback to `()` but rather `!`.
//
// revisions: nofallback fallback
//[fallback] run-pass
//[nofallback] check-fail

#![feature(never_type)]

#![cfg_attr(fallback, feature(never_type_fallback))]

struct E;

impl From<!> for E {
    fn from(_: !) -> E {
        E
    }
}

#[allow(unreachable_code)]
#[allow(dead_code)]
#[allow(unused_must_use)]
fn foo(never: !) {
    <E as From<!>>::from(never);  // Ok
    <E as From<_>>::from(never);  //[nofallback]~ ERROR trait bound `E: From<()>` is not satisfied
}

fn main() { }