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https://github.com/rust-lang/rust
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3aa14e3b2e
In its first step of computing transmutability, `rustc_transmutability` constructs a byte-level representation of type layout (`Tree`). Previously, this representation was computed for ADTs by inspecting the ADT definition and performing our own layout computations. This process was error-prone, verbose, and limited our ability to analyze many types (particularly default-repr types). In this PR, we instead construct `Tree`s from `rustc_target::abi::Layout`s. This helps ensure that layout optimizations are reflected our analyses, and increases the kinds of types we can now analyze, including: - default repr ADTs - transparent unions - `UnsafeCell`-containing types Overall, this PR expands the expressvity of `rustc_transmutability` to be much closer to the transmutability analysis performed by miri. Future PRs will work to close the remaining gaps (e.g., support for `Box`, raw pointers, `NonZero*`, coroutines, etc.).
35 lines
724 B
Rust
35 lines
724 B
Rust
//@ check-pass
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//! This UI test was introduced as check-fail by a buggy bug-fix for an ICE. In
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//! fact, this transmutation should be valid.
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#![crate_type = "lib"]
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#![feature(transmutability)]
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#![allow(dead_code)]
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use std::mem::size_of;
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mod assert {
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use std::mem::{Assume, BikeshedIntrinsicFrom};
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pub fn is_maybe_transmutable<Src, Dst>()
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where
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Dst: BikeshedIntrinsicFrom<
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Src,
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{ Assume { alignment: true, lifetimes: true, safety: true, validity: true } },
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>,
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{
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}
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}
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fn test() {
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#[repr(C, align(2))]
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struct A(u8, u8);
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#[repr(C)]
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struct B(u8, u8);
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assert_eq!(size_of::<A>(), size_of::<B>());
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assert::is_maybe_transmutable::<B, A>();
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}
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