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
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
|
//@ check-pass
//@ revisions: e2018 e2021
//@[e2018] edition:2018
//@[e2021] edition:2021
#![feature(never_patterns)]
#![allow(incomplete_features)]
#[derive(Debug, PartialEq, Eq)]
struct Pattern;
#[derive(Debug, PartialEq, Eq)]
struct Never;
#[derive(Debug, PartialEq, Eq)]
struct Other;
macro_rules! detect_pat {
($p:pat) => {
Pattern
};
(!) => {
Never
};
($($x:tt)*) => {
Other
};
}
// For backwards-compatibility, all the cases that parse as `Pattern` under the feature gate must
// have been parse errors before.
fn main() {
// For backwards compatibility this does not match `$p:pat`.
assert_eq!(detect_pat!(!), Never);
// Edition 2018 parses both of these cases as `Other`. Both editions have been parsing the
// first case as `Other` before, so we mustn't change that.
assert_eq!(detect_pat!(! | true), Other);
#[cfg(e2018)]
assert_eq!(detect_pat!(true | !), Other);
#[cfg(e2021)]
assert_eq!(detect_pat!(true | !), Pattern);
// These are never patterns; they take no body when they're in a match arm.
assert_eq!(detect_pat!((!)), Pattern);
assert_eq!(detect_pat!((true, !)), Pattern);
assert_eq!(detect_pat!(Some(!)), Pattern);
// These count as normal patterns.
assert_eq!(detect_pat!((! | true)), Pattern);
assert_eq!(detect_pat!((Ok(x) | Err(&!))), Pattern);
}
|
