Eliminate a number of uses of the *Indexable protocols.

Author: DougGregor

stdlib/private/StdlibCollectionUnittest/CheckCollectionInstance.swift.gyb

@@ -40,8 +40,8 @@ public struct CollectionMisuseResiliencyChecks {
 }
 
 % for inc, protocol, direction, end in (
-%  ('inc', '_Indexable', 'after', 'end'),
-%  ('dec', '_BidirectionalIndexable', 'before', 'start')):
+%  ('inc', 'Collection', 'after', 'end'),
+%  ('dec', 'BidirectionalCollection', 'before', 'start')):
 
 /// Test that the elements of `instances` satisfy
 /// ${'some of ' if inc == 'dec' else ''}the semantic
@@ -88,7 +88,7 @@ internal func _checkIncrementalAdvance<Instances, BaseCollection>(
   ${TRACE}
 ) where
   Instances : Collection,
-  BaseCollection : _Indexable,
+  BaseCollection : Collection,
   Instances.Iterator.Element == BaseCollection.Index {
   for i in instances {
     let d: BaseCollection.IndexDistance = sign > 0 ?
@@ -122,7 +122,7 @@ public func checkForwardIndex<Instances, BaseCollection>(
   endIndex: Instances.Iterator.Element, ${TRACE}
 ) where
   Instances : Collection,
-  BaseCollection : _Indexable,
+  BaseCollection : Collection,
   Instances.Iterator.Element == BaseCollection.Index {
 
   checkIncrementable(instances, of: baseCollection,
@@ -149,7 +149,7 @@ public func checkBidirectionalIndex<Instances, BaseCollection>(
   ${TRACE}
 ) where
   Instances: Collection,
-  BaseCollection : _BidirectionalIndexable,
+  BaseCollection : BidirectionalCollection,
   Instances.Iterator.Element == BaseCollection.Index {
 
   checkForwardIndex(instances, of: baseCollection,
@@ -185,7 +185,7 @@ public func checkRandomAccessIndex<Instances, Distances, BaseCollection>(
 ) where
   Instances : Collection,
   Distances : Collection,
-  BaseCollection : _RandomAccessIndexable,
+  BaseCollection : RandomAccessCollection,
   Instances.Iterator.Element == BaseCollection.Index,
   Distances.Iterator.Element == BaseCollection.IndexDistance {
 
@@ -214,7 +214,7 @@ public func checkAdvancesAndDistances<Instances, Distances, BaseCollection>(
 ) where
   Instances : Collection,
   Distances : Collection,
-  BaseCollection : _Indexable,
+  BaseCollection : Collection,
   Instances.Iterator.Element == BaseCollection.Index,
   Distances.Iterator.Element == BaseCollection.IndexDistance {
 

stdlib/public/SDK/Foundation/IndexSet.swift

@@ -371,7 +371,7 @@ public struct IndexSet : ReferenceConvertible, Equatable, BidirectionalCollectio
     public func intersects(integersIn range: CountableClosedRange<Element>) -> Bool { return self.intersects(integersIn: Range(range)) }
 
     // MARK: -
-    // Indexable
+    // Collection
 
     public func index(after i: Index) -> Index {
         if i.value + 1 == i.extent.upperBound {

stdlib/public/core/UnsafeBufferPointer.swift.gyb

@@ -59,7 +59,7 @@ public struct UnsafeBufferPointerIterator<Element>
 /// referenced memory and into the new collection.
 @_fixed_layout
 public struct Unsafe${Mutable}BufferPointer<Element>
-  : _${Mutable}Indexable, ${Mutable}Collection, RandomAccessCollection {
+  : ${Mutable}Collection, RandomAccessCollection {
   // FIXME: rdar://18157434 - until this is fixed, this has to be fixed layout
   // to avoid a hang in Foundation, which has the following setup:
   // struct A { struct B { let x: UnsafeMutableBufferPointer<...> } let b: B }