add Zeroable::init_zeroed

The trait function delegates to the already existing `init_zeroed`
function that returns a zeroing initializer for `Self`.

The syntax `..Zeroable::init_zeroed()` is already used by the
initialization macros to initialize all fields that are not mentioned in
the initializer with zero. Therefore it is expected that the function
also exists on the trait.

Signed-off-by: Benno Lossin <lossin@kernel.org>

Author: BennoLossin

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   implement it.
 - `unsafe fn cast_[pin_]init()` functions to unsafely change the initialized type of an initializer
 - `impl<T, E> [Pin]Init<T, E> for Result<T, E>`, so results are now (pin-)initializers
+- add `Zeroable::init_zeroed()` delegating to `init_zeroed()`
 
 ### Changed
 

src/lib.rs

@@ -1495,7 +1495,18 @@ pub unsafe trait PinnedDrop: __internal::HasPinData {
 /// ```rust,ignore
 /// let val: Self = unsafe { core::mem::zeroed() };
 /// ```
-pub unsafe trait Zeroable {}
+pub unsafe trait Zeroable {
+    /// Create a new zeroed `Self`.
+    ///
+    /// The returned initializer will write `0x00` to every byte of the given `slot`.
+    #[inline]
+    fn init_zeroed() -> impl Init<Self>
+    where
+        Self: Sized,
+    {
+        init_zeroed()
+    }
+}
 
 /// Marker trait for types that allow `Option<Self>` to be set to all zeroes in order to write
 /// `None` to that location.

tests/ui/compile-fail/init/missing_comma_with_zeroable.stderr

@@ -1,14 +1,3 @@
-error[E0782]: expected a type, found a trait
-  --> tests/ui/compile-fail/init/missing_comma_with_zeroable.rs:12:15
-   |
-12 |         a: 0..Zeroable::init_zeroed()
-   |               ^^^^^^^^
-   |
-help: you can add the `dyn` keyword if you want a trait object
-   |
-12 |         a: 0..<dyn Zeroable>::init_zeroed()
-   |               ++++         +
-
 error[E0308]: mismatched types
   --> tests/ui/compile-fail/init/missing_comma_with_zeroable.rs:11:13
    |