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In rustc it doesn't really matter what the order of the witnesses is, but I'm planning to use the witnesses for implementing the "add missing match arms" assist in rust-analyzer, and there `true` before `false` is the natural order (like `Some` before `None`), and also what the current assist does. The current order doesn't seem to be intentional; the code was created when bool ctors became their own thing, not just int ctors, but for integer, 0 before 1 is indeed the natural order.
36 lines
1.1 KiB
Rust
36 lines
1.1 KiB
Rust
fn main() {
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#[derive(Copy, Clone)]
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union U8AsBool {
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n: u8,
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b: bool,
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}
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let x = U8AsBool { n: 1 };
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unsafe {
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match x {
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// exhaustive
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U8AsBool { n: 2 } => {}
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U8AsBool { b: true } => {}
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U8AsBool { b: false } => {}
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}
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match x {
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// exhaustive
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U8AsBool { b: true } => {}
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U8AsBool { n: 0 } => {}
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U8AsBool { n: 1.. } => {}
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}
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match x {
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//~^ ERROR non-exhaustive patterns: `U8AsBool { n: 0_u8 }` and `U8AsBool { b: false }` not covered
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U8AsBool { b: true } => {}
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U8AsBool { n: 1.. } => {}
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}
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// Our approach can report duplicate witnesses sometimes.
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match (x, true) {
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//~^ ERROR non-exhaustive patterns: `(U8AsBool { n: 0_u8 }, false)`, `(U8AsBool { b: true }, false)`, `(U8AsBool { n: 0_u8 }, false)` and 1 more not covered
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(U8AsBool { b: true }, true) => {}
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(U8AsBool { b: false }, true) => {}
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(U8AsBool { n: 1.. }, true) => {}
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}
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}
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}
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