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Do not lint when range is completely included into another one #6603

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Jan 31, 2021
Merged

Do not lint when range is completely included into another one #6603

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70704db
Do not lint when range is completely included into another one
ThibsG Jan 15, 2021
0518911
Add more tests for `match_overlapping_arm` lint
ThibsG Jan 24, 2021
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12 changes: 11 additions & 1 deletion clippy_lints/src/matches.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1544,7 +1544,17 @@ where
}
},
(&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
_ => return Some((a.range(), b.range())),
_ => {
// skip if the range `a` is completely included into the range `b`
if let Ordering::Equal | Ordering::Less = a.cmp(&b) {
let kind_a = Kind::End(a.range().node.1, a.range());
let kind_b = Kind::End(b.range().node.1, b.range());
if let Ordering::Equal | Ordering::Greater = kind_a.cmp(&kind_b) {
return None;
}
}
return Some((a.range(), b.range()));
},
}
}

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30 changes: 30 additions & 0 deletions tests/ui/match_overlapping_arm.rs
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Expand Up @@ -57,6 +57,36 @@ fn overlapping() {
_ => (),
}

match 42 {
5..7 => println!("5 .. 7"),
0..10 => println!("0 .. 10"),
_ => (),
}

match 42 {
5..10 => println!("5 .. 10"),
0..=10 => println!("0 ... 10"),
_ => (),
}
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match 42 {
0..14 => println!("0 .. 14"),
5..10 => println!("5 .. 10"),
_ => (),
}
Comment on lines +72 to +76
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Huh, shouldn't rustc trigger here? the second arm is unreachable. Well, at least this lint doesn't trigger here.

A quick check on Playground shows that rustc triggers here correctly. So I assume this is a late pass lint in rustc and therefore would only trigger once the clippy lint doesn't trigger anymore.

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Yes I was a bit surprise too, I was also waiting for an unreachable warning 😅


match 42 {
5..14 => println!("5 .. 14"),
0..=10 => println!("0 ... 10"),
_ => (),
}

match 42 {
0..7 => println!("0 .. 7"),
0..=10 => println!("0 ... 10"),
_ => (),
}

/*
// FIXME(JohnTitor): uncomment this once rustfmt knows half-open patterns
match 42 {
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32 changes: 16 additions & 16 deletions tests/ui/match_overlapping_arm.stderr
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Expand Up @@ -24,39 +24,39 @@ LL | FOO..=11 => println!("0 ... 11"),
| ^^^^^^^^

error: some ranges overlap
--> $DIR/match_overlapping_arm.rs:26:9
--> $DIR/match_overlapping_arm.rs:55:9
|
LL | 0..=5 => println!("0 ... 5"),
LL | 0..11 => println!("0 .. 11"),
| ^^^^^
|
note: overlaps with this
--> $DIR/match_overlapping_arm.rs:25:9
--> $DIR/match_overlapping_arm.rs:56:9
|
LL | 2 => println!("2"),
| ^
LL | 0..=11 => println!("0 ... 11"),
| ^^^^^^

error: some ranges overlap
--> $DIR/match_overlapping_arm.rs:32:9
--> $DIR/match_overlapping_arm.rs:80:9
|
LL | 0..=2 => println!("0 ... 2"),
| ^^^^^
LL | 0..=10 => println!("0 ... 10"),
| ^^^^^^
|
note: overlaps with this
--> $DIR/match_overlapping_arm.rs:31:9
--> $DIR/match_overlapping_arm.rs:79:9
|
LL | 2 => println!("2"),
| ^
LL | 5..14 => println!("5 .. 14"),
| ^^^^^

error: some ranges overlap
--> $DIR/match_overlapping_arm.rs:55:9
--> $DIR/match_overlapping_arm.rs:85:9
|
LL | 0..11 => println!("0 .. 11"),
| ^^^^^
LL | 0..7 => println!("0 .. 7"),
| ^^^^
|
note: overlaps with this
--> $DIR/match_overlapping_arm.rs:56:9
--> $DIR/match_overlapping_arm.rs:86:9
|
LL | 0..=11 => println!("0 ... 11"),
LL | 0..=10 => println!("0 ... 10"),
| ^^^^^^

error: aborting due to 5 previous errors
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