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110 lines
3.3 KiB
Rust
110 lines
3.3 KiB
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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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 {
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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 void() {
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enum Void {}
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// This transmutation is vacuously acceptable; since one cannot construct a
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// `Void`, unsoundness cannot directly arise from transmuting a void into
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// anything else.
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assert::is_maybe_transmutable::<Void, u128>();
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assert::is_maybe_transmutable::<(), Void>(); //~ ERROR: cannot be safely transmuted
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}
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// Non-ZST uninhabited types are, nonetheless, uninhabited.
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fn yawning_void_struct() {
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enum Void {}
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struct YawningVoid(Void, u128);
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const _: () = {
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assert!(std::mem::size_of::<YawningVoid>() == std::mem::size_of::<u128>());
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// Just to be sure the above constant actually evaluated:
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assert!(false); //~ ERROR: evaluation of constant value failed
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};
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// This transmutation is vacuously acceptable; since one cannot construct a
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// `Void`, unsoundness cannot directly arise from transmuting a void into
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// anything else.
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assert::is_maybe_transmutable::<YawningVoid, u128>();
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assert::is_maybe_transmutable::<(), Void>(); //~ ERROR: cannot be safely transmuted
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}
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// Non-ZST uninhabited types are, nonetheless, uninhabited.
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fn yawning_void_enum() {
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enum Void {}
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enum YawningVoid {
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A(Void, u128),
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}
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const _: () = {
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assert!(std::mem::size_of::<YawningVoid>() == std::mem::size_of::<u128>());
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// Just to be sure the above constant actually evaluated:
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assert!(false); //~ ERROR: evaluation of constant value failed
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};
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// This transmutation is vacuously acceptable; since one cannot construct a
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// `Void`, unsoundness cannot directly arise from transmuting a void into
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// anything else.
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assert::is_maybe_transmutable::<YawningVoid, u128>();
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assert::is_maybe_transmutable::<(), Void>(); //~ ERROR: cannot be safely transmuted
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}
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// References to uninhabited types are, logically, uninhabited, but for layout
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// purposes are not ZSTs, and aren't treated as uninhabited when they appear in
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// enum variants.
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fn distant_void() {
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enum Void {}
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enum DistantVoid {
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A(&'static Void)
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}
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const _: () = {
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assert!(std::mem::size_of::<DistantVoid>() == std::mem::size_of::<usize>());
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// Just to be sure the above constant actually evaluated:
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assert!(false); //~ ERROR: evaluation of constant value failed
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};
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assert::is_maybe_transmutable::<DistantVoid, ()>();
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assert::is_maybe_transmutable::<DistantVoid, &'static Void>();
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assert::is_maybe_transmutable::<u128, DistantVoid>(); //~ ERROR: cannot be safely transmuted
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}
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fn issue_126267() {
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pub enum ApiError {}
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pub struct TokioError {
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b: bool,
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}
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pub enum Error {
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Api { source: ApiError }, // this variant is uninhabited
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Ethereum,
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Tokio { source: TokioError },
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}
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struct Src;
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type Dst = Error;
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assert::is_maybe_transmutable::<Src, Dst>(); //~ERROR: cannot be safely transmuted
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}
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