mirror of https://github.com/rust-lang/rust.git
42 lines
1.1 KiB
Rust
42 lines
1.1 KiB
Rust
#![feature(never_type)]
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#![feature(transmutability)]
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use std::mem::{Assume, TransmuteFrom};
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pub fn is_transmutable<Src, Dst>()
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where
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Dst: TransmuteFrom<Src, { Assume::SAFETY }>,
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{
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}
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fn main() {
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is_transmutable::<char, u32>();
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// `char`s can be in the following ranges:
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// - [0, 0xD7FF]
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// - [0xE000, 10FFFF]
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//
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// `Char` has variants whose tags are in the top and bottom of each range.
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// It also has generic variants which are out of bounds of these ranges, but
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// are generic on types which may be set to `!` to "disable" them in the
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// transmutability analysis.
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#[repr(u32)]
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enum Char<B, C, D> {
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A = 0,
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B = 0xD7FF,
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OverB(B) = 0xD800,
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UnderC(C) = 0xDFFF,
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C = 0xE000,
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D = 0x10FFFF,
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OverD(D) = 0x110000,
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}
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is_transmutable::<Char<!, !, !>, char>();
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is_transmutable::<Char<(), !, !>, char>();
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//~^ ERROR cannot be safely transmuted into `char`
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is_transmutable::<Char<!, (), !>, char>();
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//~^ ERROR cannot be safely transmuted into `char`
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is_transmutable::<Char<!, !, ()>, char>();
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//~^ ERROR cannot be safely transmuted into `char`
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}
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