Update library/core/src/iter/traits/iterator.rs

Co-authored-by: Jubilee <workingjubilee@gmail.com>

Author: JakenHerman

library/core/src/iter/traits/iterator.rs

@@ -3493,9 +3493,8 @@ pub trait Iterator {
     ///
     /// Takes each element, adds them together, and returns the result.
     ///
-    /// An empty iterator returns the zero value of the type except in the event
-    /// of summing primitive types that have negative zero values like f32 and f64.
-    /// An empty iterator of these types will return the negative zero value.
+    /// An empty iterator returns the *additive identity* ("zero") of the type,
+    /// which is `0` for integers and `-0.0` for floats.
     ///
     /// `sum()` can be used to sum any type implementing [`Sum`][`core::iter::Sum`],
     /// including [`Option`][`Option::sum`] and [`Result`][`Result::sum`].