[stdlib] Propagate BidirectionalIndexType docs

193 undocumented public non-operator APIs remain in core

Swift SVN r22225

stdlib/core/Bit.swift

@@ -27,8 +27,9 @@ public enum Bit : Int, RandomAccessIndexType, Reflectable {
     return .One
   }
 
-  /// Return the previous consecutive value in a discrete sequence of
-  /// `Bit` values.
+  /// Returns the previous consecutive value before `self`.
+  ///
+  /// Requires: `self != .Zero`.
   public func predecessor() -> Bit {
     _precondition(self == .One, "Can't decrement past zero")
     return .Zero

stdlib/core/Concatenate.swift.gyb

@@ -153,7 +153,9 @@ struct ${Index}<
   }
 
   % if traversal == 'Bidirectional':
-  /// Return an index for the previous position.
+  /// Returns the previous consecutive value before `self`.
+  ///
+  /// Requires: the previous value is representable.
   func predecessor() -> ${Index} {
 
     var outer = _outer

stdlib/core/Dictionary.swift

@@ -1680,6 +1680,9 @@ public struct DictionaryIndex<Key : Hashable, Value> :
 
   public typealias Index = DictionaryIndex<Key, Value>
 
+  /// Returns the previous consecutive value before `self`.
+  ///
+  /// Requires: the previous value is representable.
   public func predecessor() -> Index {
     if _fastPath(_guaranteedNative) {
       return ._Native(_nativeIndex.predecessor())

stdlib/core/FixedPoint.swift.gyb

@@ -287,6 +287,9 @@ extension ${Self} : RandomAccessIndexType {
   func successor() -> ${Self} {
     return self &+ 1
   }
+  /// Returns the previous consecutive value before `self`.
+  ///
+  /// Requires: the previous value is representable.
   @transparent public
   func predecessor() -> ${Self} {
     return self &- 1

stdlib/core/Reverse.swift.gyb

@@ -40,6 +40,9 @@ public struct ${Index}<I: ${IndexProtocol}> : ${IndexProtocol} {
     return ${Index}(_base.predecessor())
   }
   
+  /// Returns the previous consecutive value before `self`.
+  ///
+  /// Requires: the previous value is representable.
   public func predecessor() -> ${Index} {
     return ${Index}(_base.successor())
   }

stdlib/core/String.swift

@@ -345,6 +345,9 @@ extension String : CollectionType {
       return Index(_endBase)
     }
 
+  /// Returns the previous consecutive value before `self`.
+  ///
+  /// Requires: the previous value is representable.
     public func predecessor() -> Index {
       _precondition(_base != _base._viewStartIndex,
           "can not decrement startIndex")

stdlib/core/StringUnicodeScalarView.swift

@@ -61,6 +61,9 @@ extension String {
         return Index(_position + length, _core)
       }
 
+      /// Returns the previous consecutive value before `self`.
+      ///
+      /// Requires: the previous value is representable.
       public func predecessor() -> Index {
         var i = _position
         let codeUnit = _core[--i]

stdlib/core/UnsafePointer.swift.gyb

@@ -358,6 +358,9 @@ public struct ${Self}<T>
   public func successor() -> ${Self} {
     return self + 1
   }
+  /// Returns the previous consecutive value before `self`.
+  ///
+  /// Requires: the previous value is representable.
   public func predecessor() -> ${Self} {
     return self - 1
   }