mirror of https://github.com/rust-lang/rust
45 lines
1.1 KiB
Rust
45 lines
1.1 KiB
Rust
//@ build-fail
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trait Tr {
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const A: u8 = 255;
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// This should not be a constant evaluation error (overflow). The value of
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// `Self::A` must not be assumed to hold inside the trait.
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const B: u8 = Self::A + 1;
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//~^ ERROR evaluation of `<() as Tr>::B` failed
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}
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// An impl that doesn't override any constant will NOT cause a const eval error
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// just because it's defined, but only if the bad constant is used anywhere.
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// This matches the behavior without defaults.
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impl Tr for () {}
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// An impl that overrides either constant with a suitable value will be fine.
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impl Tr for u8 {
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const A: u8 = 254;
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}
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impl Tr for u16 {
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const B: u8 = 0;
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}
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impl Tr for u32 {
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const A: u8 = 254;
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const B: u8 = 0;
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}
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fn main() {
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assert_eq!(<() as Tr>::A, 255);
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assert_eq!(<() as Tr>::B, 0); // causes the error above
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//~^ constant
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assert_eq!(<u8 as Tr>::A, 254);
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assert_eq!(<u8 as Tr>::B, 255);
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assert_eq!(<u16 as Tr>::A, 255);
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assert_eq!(<u16 as Tr>::B, 0);
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assert_eq!(<u32 as Tr>::A, 254);
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assert_eq!(<u32 as Tr>::B, 0);
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}
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