doc: apply suggestions

library/alloc/src/macros.rs

@@ -29,8 +29,9 @@
 /// to the same boxed integer value, not five references pointing to independently
 /// boxed integers.
 ///
-/// Also, note that `[T; 0]` is a valid initializer. This will initialize (or call)
-/// `T` but not populate the vector with it, so be mindful of side effects.
+/// Also, note that `vec![expr; 0]` is allowed, and produces an empty vector.
+/// This will still evaluate `expr`, however, and immediately drop the resulting value, so
+/// be mindful of side effects.
 ///
 /// [`Vec`]: crate::vec::Vec
 #[cfg(not(test))]

library/std/src/primitive_docs.rs

@@ -489,8 +489,9 @@ mod prim_pointer {}
 /// * A repeat expression `[x; N]`, which produces an array with `N` copies of `x`.
 ///   The type of `x` must be [`Copy`].
 ///
-/// Note that `[x; 0]` is a valid repeat expression. This will produce an empty array
-/// but will also initialize (or call) `x`, which may produce side effects.
+/// Note that `[expr; 0]` is allowed, and produces an empty array.
+/// This will still evaluate `expr`, however, and immediately drop the resulting value, so
+/// be mindful of side effects.
 ///
 /// Arrays of *any* size implement the following traits if the element type allows it:
 ///