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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
44 lines
1023 B
Rust
44 lines
1023 B
Rust
#![crate_type = "lib"]
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#![feature(transmutability)]
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#![allow(dead_code, incomplete_features, non_camel_case_types)]
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use std::mem::MaybeUninit;
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mod assert {
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use std::mem::{Assume, TransmuteFrom};
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pub fn is_maybe_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 validity() {
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// An initialized byte is a valid uninitialized byte.
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assert::is_maybe_transmutable::<u8, MaybeUninit<u8>>();
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// An uninitialized byte is never a valid initialized byte.
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assert::is_maybe_transmutable::<MaybeUninit<u8>, u8>(); //~ ERROR: cannot be safely transmuted
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}
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fn padding() {
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#[repr(align(8))]
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struct Align8;
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#[repr(u8)]
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enum ImplicitlyPadded {
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A(Align8),
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}
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#[repr(u8)]
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enum V0 {
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V0 = 0,
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}
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#[repr(C)]
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struct ExplicitlyPadded(V0, MaybeUninit<[u8; 7]>);
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assert::is_maybe_transmutable::<ExplicitlyPadded, ImplicitlyPadded>();
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assert::is_maybe_transmutable::<ImplicitlyPadded, ExplicitlyPadded>();
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}
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