Rollup merge of #137054 - jhpratt:phantom-variance, r=Mark-Simulacrum

Make phantom variance markers transparent

Author: matthiaskrgr

library/core/src/marker/variance.rs

@@ -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.
     ///
@@ -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.
     ///
@@ -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 ()>);
 }
 
@@ -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.
     ///
@@ -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.
     ///
@@ -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>);
 }