Bump to 3.20.0 (#307)

* Small clean ups and formatting

* Bump to version 3.20.0

* fmt

Author: fitzgen

CHANGELOG.md

@@ -28,6 +28,23 @@ Released YYYY-MM-DD.
 
 --------------------------------------------------------------------------------
 
+## 3.20.0
+
+Released 2026-02-18.
+
+### Added
+
+* Added the `bumpalo::collections::Vec::pop_if` method.
+
+### Fixed
+
+* Fixed a bug in the `bumpalo::collections::String::retain` method in the face
+  of panics.
+* Made `bumpalo::collections::Box<T>` covariant with `T` (just like
+  `std::boxed::Box<T>`).
+
+--------------------------------------------------------------------------------
+
 ## 3.19.1
 
 Released 2025-12-16.

Cargo.toml

@@ -10,7 +10,7 @@ name = "bumpalo"
 readme = "README.md"
 repository = "https://github.com/fitzgen/bumpalo"
 rust-version = "1.71.1"
-version = "3.19.1"
+version = "3.20.0"
 
 [package.metadata.docs.rs]
 all-features = true

src/boxed.rs

@@ -234,7 +234,8 @@ impl<'a, T: ?Sized> Box<'a, T> {
     /// ```
     #[inline]
     pub unsafe fn from_raw(raw: *mut T) -> Self {
-        // Safety - The preconditions of the unsafe from_raw function ensure raw is valid
+        // Safety: part of this function's unsafe contract is that the raw
+        // pointer be non-null.
         Box(unsafe { NonNull::new_unchecked(raw) }, PhantomData)
     }
 
@@ -551,15 +552,16 @@ impl<'a, T: ?Sized> fmt::Pointer for Box<'a, T> {
     }
 }
 
-//This function tests that box isn't contravariant.
+///This function tests that box isn't contravariant.
+///
 /// ```compile_fail
 /// fn _box_is_not_contravariant<'sub, 'sup :'sub>(
-///   a: Box<&'sup u32>,
-///  b: Box<&'sub u32>,
-///   f: impl Fn(Box<&'sup u32>),
+///     a: Box<&'sup u32>,
+///     b: Box<&'sub u32>,
+///     f: impl Fn(Box<&'sup u32>),
 /// ) {
-///   f(a);
-///   f(b);
+///     f(a);
+///     f(b);
 /// }
 /// ```
 #[cfg(doctest)]
@@ -569,14 +571,18 @@ impl<'a, T: ?Sized> Deref for Box<'a, T> {
     type Target = T;
 
     fn deref(&self) -> &T {
-        // Safety - The box points to a valid instance of T allocated with a Bumpalo arena.
+        // Safety: Our pointer always points to a valid instance of `T`
+        // allocated within a `Bump` and the `&self` borrow ensures that there
+        // are no active exclusive borrows.
         unsafe { self.0.as_ref() }
     }
 }
 
 impl<'a, T: ?Sized> DerefMut for Box<'a, T> {
     fn deref_mut(&mut self) -> &mut T {
-        // Safety - The box points to a valid instance of T allocated with a Bumpalo arena.
+        // Safety: Our pointer always points to a valid instance of `T`
+        // allocated within a `Bump` and the `&mut self` borrow ensures that
+        // there are no other active borrows.
         unsafe { self.0.as_mut() }
     }
 }

tests/all/boxed.rs

@@ -23,8 +23,7 @@ fn test_box_basic() {
     assert_eq!("world", &*value);
 }
 
-// This function tests that Box is covariant.
-// If you change the PhantomData<&'a T> in Box to PhantomData<&'a mut T> the test fails the borrow checker.
+// This function tests that `Box` is covariant.
 fn _box_is_covariant<'sup, 'sub: 'sup>(
     a: Box<&'sup u32>,
     b: Box<&'sub u32>,