Mark NonZeroLayout::padding_needed_for const

Author: TimDiekmann

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 - Provide default implementation for `realloc`
 - Don't reexport `Layout`
-- Make `NonZeroLayout::size` and `align` const
+- Make `NonZeroLayout::size`, `padding_needed_for` and `align` const
 
 # v0.5
 

src/alloc/layout.rs

@@ -134,7 +134,7 @@ impl NonZeroLayout {
     /// satisfy this constraint is to ensure `align <= self.align()`.
     #[inline]
     #[must_use]
-    pub fn padding_needed_for(&self, align: NonZeroUsize) -> usize {
+    pub const fn padding_needed_for(&self, align: NonZeroUsize) -> usize {
         // Rounded up value is:
         //   len_rounded_up = (len + align - 1) & !(align - 1);
         // and then we return the padding difference: `len_rounded_up - len`.