[stdlib] Use double space as sentence separator in IteratorType.next() docs.

Author: PatrickPijnappel

stdlib/public/core/Algorithm.swift

@@ -85,7 +85,7 @@ public struct EnumeratedIterator<
   public typealias Element = (offset: Int, element: Base.Element)
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   public mutating func next() -> Element? {
     guard let b = _base.next() else { return nil }
     defer { _count += 1 }

stdlib/public/core/Collection.swift

@@ -82,7 +82,7 @@ public struct IndexingIterator<Elements : Indexable>
   }
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   public mutating func next() -> Elements._Element? {
     if _position == _elements.endIndex { return nil }
     let element = _elements[_position]

stdlib/public/core/CollectionOfOne.swift

@@ -20,7 +20,7 @@ public struct IteratorOverOne<Element> : IteratorProtocol, Sequence {
   }
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   ///
   /// - Precondition: `next()` has not been applied to a copy of `self`
   ///   since the copy was made.

stdlib/public/core/ExistentialCollection.swift.gyb

@@ -67,7 +67,7 @@ public struct AnyIterator<Element> : IteratorProtocol {
   }
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   public func next() -> Element? {
     return _box.next()
   }
@@ -93,7 +93,7 @@ internal class _AnyIteratorBoxBase<Element>
   : _AnyIteratorBase, IteratorProtocol {
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   ///
   /// - Note: Subclasses must override this method.
   internal func next() -> Element? { _abstract() }

stdlib/public/core/Flatten.swift.gyb

@@ -28,7 +28,7 @@ public struct FlattenIterator<
   }
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   ///
   /// - Precondition: `next()` has not been applied to a copy of `self`
   ///   since the copy was made.

stdlib/public/core/HashedCollections.swift.gyb

@@ -3984,7 +3984,7 @@ public struct ${Self}Iterator<${TypeParametersDecl}> : IteratorProtocol {
   }
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   public mutating func next() -> ${Sequence}? {
     if _fastPath(_guaranteedNative) {
       return _nativeNext()

stdlib/public/core/Join.swift

@@ -37,7 +37,7 @@ public struct JoinedIterator<
   }
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   public mutating func next() -> Base.Element.Iterator.Element? {
     repeat {
       switch _state {

stdlib/public/core/Map.swift

@@ -17,7 +17,7 @@ public struct LazyMapIterator<
   Base : IteratorProtocol, Element
 > : IteratorProtocol, Sequence {
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   ///
   /// - Precondition: `next()` has not been applied to a copy of `self`
   ///   since the copy was made.

stdlib/public/core/Range.swift

@@ -23,7 +23,7 @@ public struct RangeIterator<
   }
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   public mutating func next() -> Element? {
     if startIndex == endIndex { return nil }
     let element = startIndex

stdlib/public/core/Sequence.swift

@@ -27,7 +27,7 @@ public protocol IteratorProtocol {
   associatedtype Element
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   ///
   /// - Precondition: `next()` has not been applied to a copy of `self`
   ///   since the copy was made.
@@ -635,7 +635,7 @@ public struct IteratorSequence<
   }
 
   /// Advance to the next element and return it, or `nil` if no next element
-  /// exists. Once `nil` has been returned, all subsequent calls return `nil`.
+  /// exists.  Once `nil` has been returned, all subsequent calls return `nil`.
   ///
   /// - Precondition: `next()` has not been applied to a copy of `self`
   ///   since the copy was made.