Skip to content

Make phantom variance markers transparent #137054

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Mar 4, 2025
Merged

Make phantom variance markers transparent #137054

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
12 changes: 12 additions & 0 deletions library/core/src/marker/variance.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,8 @@ phantom_lifetime! {
/// For all `'a`, the following are guaranteed:
/// * `size_of::<PhantomCovariantLifetime<'a>>() == 0`
/// * `align_of::<PhantomCovariantLifetime<'a>>() == 1`
#[rustc_pub_transparent]
#[repr(transparent)]
pub struct PhantomCovariantLifetime<'a>(PhantomCovariant<&'a ()>);
/// Zero-sized type used to mark a lifetime as contravariant.
///
Expand All @@ -149,6 +151,8 @@ phantom_lifetime! {
/// For all `'a`, the following are guaranteed:
/// * `size_of::<PhantomContravariantLifetime<'a>>() == 0`
/// * `align_of::<PhantomContravariantLifetime<'a>>() == 1`
#[rustc_pub_transparent]
#[repr(transparent)]
pub struct PhantomContravariantLifetime<'a>(PhantomContravariant<&'a ()>);
/// Zero-sized type used to mark a lifetime as invariant.
///
Expand All @@ -162,6 +166,8 @@ phantom_lifetime! {
/// For all `'a`, the following are guaranteed:
/// * `size_of::<PhantomInvariantLifetime<'a>>() == 0`
/// * `align_of::<PhantomInvariantLifetime<'a>>() == 1`
#[rustc_pub_transparent]
#[repr(transparent)]
pub struct PhantomInvariantLifetime<'a>(PhantomInvariant<&'a ()>);
}

Expand All @@ -179,6 +185,8 @@ phantom_type! {
/// For all `T`, the following are guaranteed:
/// * `size_of::<PhantomCovariant<T>>() == 0`
/// * `align_of::<PhantomCovariant<T>>() == 1`
#[rustc_pub_transparent]
#[repr(transparent)]
pub struct PhantomCovariant<T>(PhantomData<fn() -> T>);
/// Zero-sized type used to mark a type parameter as contravariant.
///
Expand All @@ -193,6 +201,8 @@ phantom_type! {
/// For all `T`, the following are guaranteed:
/// * `size_of::<PhantomContravariant<T>>() == 0`
/// * `align_of::<PhantomContravariant<T>>() == 1`
#[rustc_pub_transparent]
#[repr(transparent)]
pub struct PhantomContravariant<T>(PhantomData<fn(T)>);
/// Zero-sized type used to mark a type parameter as invariant.
///
Expand All @@ -206,6 +216,8 @@ phantom_type! {
/// For all `T`, the following are guaranteed:
/// * `size_of::<PhantomInvariant<T>>() == 0`
/// * `align_of::<PhantomInvariant<T>>() == 1`
#[rustc_pub_transparent]
#[repr(transparent)]
pub struct PhantomInvariant<T>(PhantomData<fn(T) -> T>);
}

Expand Down
Loading