d2061faf9e
* applying * binding * complex * constituent * demonstrate * desugaring * exact * expression * for * functionalities * github * implementation * infers * multiple conflicting traits * mutable * necessarily * nightly * nonexistent * optional * parameter * reassignments * resources * substitution * suggestion * that * that array is * using the Signed-off-by: Josh Soref <2119212+jsoref@users.noreply.github.com>
54 lines
1.9 KiB
Rust
54 lines
1.9 KiB
Rust
#![feature(stmt_expr_attributes)]
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#![allow(clippy::let_unit_value, invalid_value)]
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use std::mem::MaybeUninit;
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union MyOwnMaybeUninit {
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value: u8,
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uninit: (),
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}
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fn main() {
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let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
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// This is OK, because ZSTs do not contain data.
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let _: () = unsafe { MaybeUninit::uninit().assume_init() };
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// This is OK, because `MaybeUninit` allows uninitialized data.
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let _: MaybeUninit<usize> = unsafe { MaybeUninit::uninit().assume_init() };
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// This is OK, because all constituent types are uninit-compatible.
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let _: (MaybeUninit<usize>, MaybeUninit<bool>) = unsafe { MaybeUninit::uninit().assume_init() };
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// This is OK, because all constituent types are uninit-compatible.
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let _: (MaybeUninit<usize>, [MaybeUninit<bool>; 2]) = unsafe { MaybeUninit::uninit().assume_init() };
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// This is OK, because our own MaybeUninit is just as fine as the one from core.
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let _: MyOwnMaybeUninit = unsafe { MaybeUninit::uninit().assume_init() };
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// This is OK, because empty arrays don't contain data.
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let _: [u8; 0] = unsafe { MaybeUninit::uninit().assume_init() };
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// Was a false negative.
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let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
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polymorphic::<()>();
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polymorphic_maybe_uninit_array::<10>();
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polymorphic_maybe_uninit::<u8>();
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fn polymorphic<T>() {
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// We are conservative around polymorphic types.
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let _: T = unsafe { MaybeUninit::uninit().assume_init() };
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}
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fn polymorphic_maybe_uninit_array<const N: usize>() {
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// While the type is polymorphic, MaybeUninit<u8> is not.
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let _: [MaybeUninit<u8>; N] = unsafe { MaybeUninit::uninit().assume_init() };
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}
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fn polymorphic_maybe_uninit<T>() {
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// The entire type is polymorphic, but it's wrapped in a MaybeUninit.
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let _: MaybeUninit<T> = unsafe { MaybeUninit::uninit().assume_init() };
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}
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}
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