Slight changes to index(_:offsetBy:) discussion.

Author: natecook1000

stdlib/public/core/Array.swift

@@ -438,7 +438,7 @@ extension Array: RandomAccessCollection, MutableCollection {
   /// - Returns: An index offset by `distance` from the index `i`. If
   ///   `distance` is positive, this is the same value as the result of
   ///   `distance` calls to `index(after:)`. If `distance` is negative, this
-  ///   is the same value as the result of `-distance` calls to
+  ///   is the same value as the result of `abs(distance)` calls to
   ///   `index(before:)`.
   @inlinable
   public func index(_ i: Int, offsetBy distance: Int) -> Int {

stdlib/public/core/ArraySlice.swift

@@ -261,7 +261,7 @@ extension ArraySlice: RandomAccessCollection, MutableCollection {
   /// - Returns: An index offset by `distance` from the index `i`. If
   ///   `distance` is positive, this is the same value as the result of
   ///   `distance` calls to `index(after:)`. If `distance` is negative, this
-  ///   is the same value as the result of `-distance` calls to
+  ///   is the same value as the result of `abs(distance)` calls to
   ///   `index(before:)`.
   @inlinable
   public func index(_ i: Int, offsetBy distance: Int) -> Int {

stdlib/public/core/Collection.swift

@@ -669,7 +669,7 @@ public protocol Collection: Sequence where SubSequence: Collection {
   /// - Returns: An index offset by `distance` from the index `i`. If
   ///   `distance` is positive, this is the same value as the result of
   ///   `distance` calls to `index(after:)`. If `distance` is negative, this
-  ///   is the same value as the result of `-distance` calls to
+  ///   is the same value as the result of `abs(distance)` calls to
   ///   `index(before:)`.
   ///
   /// - Complexity: O(1) if the collection conforms to
@@ -874,7 +874,7 @@ extension Collection {
   /// - Returns: An index offset by `distance` from the index `i`. If
   ///   `distance` is positive, this is the same value as the result of
   ///   `distance` calls to `index(after:)`. If `distance` is negative, this
-  ///   is the same value as the result of `-distance` calls to
+  ///   is the same value as the result of `abs(distance)` calls to
   ///   `index(before:)`.
   ///
   /// - Complexity: O(1) if the collection conforms to

stdlib/public/core/ContiguousArray.swift

@@ -170,7 +170,7 @@ extension ContiguousArray: RandomAccessCollection, MutableCollection {
   /// - Returns: An index offset by `distance` from the index `i`. If
   ///   `distance` is positive, this is the same value as the result of
   ///   `distance` calls to `index(after:)`. If `distance` is negative, this
-  ///   is the same value as the result of `-distance` calls to
+  ///   is the same value as the result of `abs(distance)` calls to
   ///   `index(before:)`.
   @inlinable
   public func index(_ i: Int, offsetBy distance: Int) -> Int {

stdlib/public/core/RandomAccessCollection.swift

@@ -223,7 +223,7 @@ where Index : Strideable,
   /// - Returns: An index offset by `distance` from the index `i`. If
   ///   `distance` is positive, this is the same value as the result of
   ///   `distance` calls to `index(after:)`. If `distance` is negative, this
-  ///   is the same value as the result of `-distance` calls to
+  ///   is the same value as the result of `abs(distance)` calls to
   ///   `index(before:)`.
   ///
   /// - Complexity: O(1)

stdlib/public/core/StringRangeReplaceableCollection.swift

@@ -150,16 +150,17 @@ extension String : StringProtocol, RangeReplaceableCollection {
   ///     print(s[i])
   ///     // Prints "t"
   ///
-  /// The value passed as `distance` must not offset `i` beyond the bounds of the
-  /// collection.
+  /// The value passed as `distance` must not offset `i` beyond the bounds of
+  /// the collection.
   ///
   /// - Parameters:
   ///   - i: A valid index of the collection.
   ///   - distance: The distance to offset `i`.
-  /// - Returns: An index offset by `distance` from the index `i`. If `distance` is positive,
-  ///   this is the same value as the result of `distance` calls to `index(after:)`.
-  ///   If `distance` is negative, this is the same value as the result of `-distance` calls
-  ///   to `index(before:)`.
+  /// - Returns: An index offset by `distance` from the index `i`. If
+  ///   `distance` is positive, this is the same value as the result of
+  ///   `distance` calls to `index(after:)`. If `distance` is negative, this
+  ///   is the same value as the result of `abs(distance)` calls to
+  ///   `index(before:)`.
   ///
   /// - Complexity: O(*k*), where *k* is the absolute value of `distance`.
   public func index(_ i: Index, offsetBy distance: IndexDistance) -> Index {