1ad218f3af
As our implementation of MCP411 nears completion and we begin to solicit testing, it's no longer reasonable to expect testers to type or remember `BikeshedIntrinsicFrom`. The name degrades the ease-of-reading of documentation, and the overall experience of using compiler safe transmute. Tentatively, we'll instead adopt `TransmuteFrom`. This name seems to be the one most likely to be stabilized, after discussion on Zulip [1]. We may want to revisit the ordering of `Src` and `Dst` before stabilization, at which point we'd likely consider `TransmuteInto` or `Transmute`. [1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20should.20.60BikeshedIntrinsicFrom.60.20be.20named.3F
92 lines
1.7 KiB
Rust
92 lines
1.7 KiB
Rust
//@ check-pass
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//! Accept lifetime extensions with `Assume::LIFETIMES`.
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#![feature(transmutability, core_intrinsics)]
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use std::mem::{Assume, TransmuteFrom};
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unsafe fn transmute<Src, Dst>(src: Src) -> Dst
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where
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Dst: TransmuteFrom<Src, { Assume::SAFETY.and(Assume::LIFETIMES) }>,
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{
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core::intrinsics::transmute_unchecked(src)
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}
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mod bare {
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use super::*;
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fn extend_bare<'a>(src: &'a u8) -> &'static u8 {
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unsafe { transmute(src) }
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}
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}
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mod nested {
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use super::*;
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fn extend_nested<'a>(src: &'a &'a u8) -> &'a &'static u8 {
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unsafe { transmute(src) }
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}
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}
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mod tuple {
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use super::*;
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fn extend_unit<'a>(src: (&'a u8,)) -> (&'static u8,) {
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unsafe { transmute(src) }
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}
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fn extend_pair<'a>(src: (&'a u8, u8)) -> (&'static u8, u8) {
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unsafe { transmute(src) }
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}
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}
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mod r#struct {
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use super::*;
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struct Struct<'a>(&'a u8);
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fn extend_struct<'a>(src: Struct<'a>) -> Struct<'static> {
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unsafe { transmute(src) }
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}
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}
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mod r#enum {
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use super::*;
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enum Single<'a> {
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A(&'a u8),
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}
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fn extend_single<'a>(src: Single<'a>) -> Single<'static> {
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unsafe { transmute(src) }
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}
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enum Multi<'a> {
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A(&'a u8),
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B,
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C,
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}
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fn extend_multi<'a>(src: Multi<'a>) -> Multi<'static> {
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unsafe { transmute(src) }
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}
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}
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mod hrtb {
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use super::*;
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fn call_extend_hrtb<'a>(src: &'a u8) -> &'static u8 {
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unsafe { extend_hrtb(src) }
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}
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unsafe fn extend_hrtb<'a>(src: &'a u8) -> &'static u8
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where
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for<'b> &'b u8: TransmuteFrom<&'a u8, { Assume::LIFETIMES }>,
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{
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core::intrinsics::transmute_unchecked(src)
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}
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}
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fn main() {}
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