8f1cec8d84
This patch enables support for references in Safe Transmute, by generating nested obligations during trait selection. Specifically, when we call `confirm_transmutability_candidate(...)`, we now recursively traverse the `rustc_transmute::Answer` tree and create obligations for all the `Answer` variants, some of which include multiple nested `Answer`s. Also, to handle recursive types, enable support for coinduction for the Safe Transmute trait (`BikeshedIntrinsicFrom`) by adding the `#[rustc_coinduction]` annotation. Also fix some small logic issues when reducing the `or` and `and` combinations in `rustc_transmute`, so that we don't end up with additional redundant `Answer`s in the tree. Co-authored-by: Jack Wrenn <jack@wrenn.fyi>
25 lines
587 B
Rust
25 lines
587 B
Rust
// check-fail
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#![feature(transmutability)]
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mod assert {
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use std::mem::{Assume, BikeshedIntrinsicFrom};
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pub struct Context;
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pub fn is_maybe_transmutable<Src, Dst>()
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where
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Dst: BikeshedIntrinsicFrom<Src, Context, {
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Assume {
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alignment: true,
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lifetimes: true,
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safety: true,
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validity: true,
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}
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}>
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{}
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}
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fn main() {
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#[repr(C)] struct Unit;
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assert::is_maybe_transmutable::<&'static Unit, &'static u8>(); //~ ERROR `Unit` cannot be safely transmuted into `u8`
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}
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