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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
60 lines
1.7 KiB
Rust
60 lines
1.7 KiB
Rust
//@ check-pass
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//! An array must inherit the alignment of its inner type.
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#![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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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, {
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Assume::ALIGNMENT
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.and(Assume::LIFETIMES)
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.and(Assume::SAFETY)
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.and(Assume::VALIDITY)
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}>
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{}
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}
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#[derive(Clone, Copy)] #[repr(u8)] enum Ox00 { V = 0x00 }
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#[derive(Clone, Copy)] #[repr(u8)] enum Ox01 { V = 0x01 }
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#[derive(Clone, Copy)] #[repr(u8)] enum OxFF { V = 0xFF }
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#[repr(C)]
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union Uninit {
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a: (),
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b: OxFF,
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}
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#[repr(C, align(2))] struct align_2(Ox00);
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fn len_0() {
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#[repr(C)] struct ImplicitlyPadded([align_2; 0], Ox01);
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#[repr(C)] struct ExplicitlyPadded(Ox01, Uninit);
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#[repr(C)] struct Struct();
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assert::is_maybe_transmutable::<ImplicitlyPadded, ExplicitlyPadded>();
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assert::is_maybe_transmutable::<ExplicitlyPadded, ImplicitlyPadded>();
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}
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fn len_1() {
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#[repr(C)] struct ImplicitlyPadded([align_2; 1], Ox01);
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#[repr(C)] struct ExplicitlyPadded(Ox00, Uninit, Ox01, Uninit);
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#[repr(C)] struct Struct();
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assert::is_maybe_transmutable::<ImplicitlyPadded, ExplicitlyPadded>();
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assert::is_maybe_transmutable::<ExplicitlyPadded, ImplicitlyPadded>();
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}
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fn len_2() {
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#[repr(C)] struct ImplicitlyPadded([align_2; 2], Ox01);
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#[repr(C)] struct ExplicitlyPadded(Ox00, Uninit, Ox00, Uninit, Ox01, Uninit);
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#[repr(C)] struct Struct();
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assert::is_maybe_transmutable::<ImplicitlyPadded, ExplicitlyPadded>();
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assert::is_maybe_transmutable::<ExplicitlyPadded, ImplicitlyPadded>();
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}
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