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Rollup merge of rust-lang#123301 - Nadrieril:unions, r=compiler-errors pattern analysis: fix union handling Little known fact: rust supports union patterns. Exhaustiveness handles them soundly but reports nonsensical missing patterns. This PR fixes the reported patterns and documents what we're doing. r? `@compiler-errors`
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,35 @@ | ||
fn main() { | ||
#[derive(Copy, Clone)] | ||
union U8AsBool { | ||
n: u8, | ||
b: bool, | ||
} | ||
|
||
let x = U8AsBool { n: 1 }; | ||
unsafe { | ||
match x { | ||
// exhaustive | ||
U8AsBool { n: 2 } => {} | ||
U8AsBool { b: true } => {} | ||
U8AsBool { b: false } => {} | ||
} | ||
match x { | ||
// exhaustive | ||
U8AsBool { b: true } => {} | ||
U8AsBool { n: 0 } => {} | ||
U8AsBool { n: 1.. } => {} | ||
} | ||
match x { | ||
//~^ ERROR non-exhaustive patterns: `U8AsBool { n: 0_u8 }` and `U8AsBool { b: false }` not covered | ||
U8AsBool { b: true } => {} | ||
U8AsBool { n: 1.. } => {} | ||
} | ||
// Our approach can report duplicate witnesses sometimes. | ||
match (x, true) { | ||
//~^ ERROR non-exhaustive patterns: `(U8AsBool { n: 0_u8 }, false)`, `(U8AsBool { b: false }, false)`, `(U8AsBool { n: 0_u8 }, false)` and 1 more not covered | ||
(U8AsBool { b: true }, true) => {} | ||
(U8AsBool { b: false }, true) => {} | ||
(U8AsBool { n: 1.. }, true) => {} | ||
} | ||
} | ||
} |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,34 @@ | ||
error[E0004]: non-exhaustive patterns: `U8AsBool { n: 0_u8 }` and `U8AsBool { b: false }` not covered | ||
--> $DIR/unions.rs:22:15 | ||
| | ||
LL | match x { | ||
| ^ patterns `U8AsBool { n: 0_u8 }` and `U8AsBool { b: false }` not covered | ||
| | ||
note: `U8AsBool` defined here | ||
--> $DIR/unions.rs:3:11 | ||
| | ||
LL | union U8AsBool { | ||
| ^^^^^^^^ | ||
= note: the matched value is of type `U8AsBool` | ||
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms | ||
| | ||
LL ~ U8AsBool { n: 1.. } => {}, | ||
LL + U8AsBool { n: 0_u8 } | U8AsBool { b: false } => todo!() | ||
| | ||
|
||
error[E0004]: non-exhaustive patterns: `(U8AsBool { n: 0_u8 }, false)`, `(U8AsBool { b: false }, false)`, `(U8AsBool { n: 0_u8 }, false)` and 1 more not covered | ||
--> $DIR/unions.rs:28:15 | ||
| | ||
LL | match (x, true) { | ||
| ^^^^^^^^^ patterns `(U8AsBool { n: 0_u8 }, false)`, `(U8AsBool { b: false }, false)`, `(U8AsBool { n: 0_u8 }, false)` and 1 more not covered | ||
| | ||
= note: the matched value is of type `(U8AsBool, bool)` | ||
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown, or multiple match arms | ||
| | ||
LL ~ (U8AsBool { n: 1.. }, true) => {}, | ||
LL + _ => todo!() | ||
| | ||
|
||
error: aborting due to 2 previous errors | ||
|
||
For more information about this error, try `rustc --explain E0004`. |