[SE-0157] Standard library uses of Recursive Protocol Constraints

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 {
 
@@ -257,8 +257,7 @@ public func checkCollection<${genericParam}, C : Collection>(
   ${TRACE},
   resiliencyChecks: CollectionMisuseResiliencyChecks = .all,
   sameValue: (${Element}, ${Element}) -> Bool
-) where C.Iterator.Element == ${Element},
-  C.SubSequence : Collection {
+) where C.Iterator.Element == ${Element} {
 
   checkForwardCollection(expected, collection, message(),
     stackTrace: stackTrace, showFrame: showFrame, file: file, line: line,
@@ -278,7 +277,6 @@ public func check${Traversal}Collection<
   resiliencyChecks: CollectionMisuseResiliencyChecks = .all
 ) where
   C.Iterator.Element == ${Element},
-  C.SubSequence : ${TraversalCollection},
   ${Element} : Equatable {
 
   check${Traversal}Collection(
@@ -298,8 +296,7 @@ public func check${Traversal}Collection<
   resiliencyChecks: CollectionMisuseResiliencyChecks = .all,
   sameValue: (${Element}, ${Element}) -> Bool
 ) where
-  C.Iterator.Element == ${Element},
-  C.SubSequence : ${TraversalCollection} {
+  C.Iterator.Element == ${Element} {
 
   checkOneLevelOf${Traversal}Collection(expected, collection, ${trace},
     resiliencyChecks: resiliencyChecks, sameValue: sameValue)
@@ -504,8 +501,7 @@ ${genericParam}, S : ${TraversalCollection}
   resiliencyChecks: CollectionMisuseResiliencyChecks = .all,
   sameValue: (${Element}, ${Element}) -> Bool
 ) where
-  S.Iterator.Element == ${Element},
-  S.SubSequence : ${TraversalCollection} {
+  S.Iterator.Element == ${Element} {
 
   let expectedArray = Array(expected)
 

stdlib/private/StdlibCollectionUnittest/CheckCollectionType.swift.gyb

@@ -471,16 +471,9 @@ internal enum _SubSequenceSubscriptOnRangeMode {
 %{
   from gyb_stdlib_support import collectionForTraversal
   def testConstraints(protocol):
-    if protocol == 'Collection':
-      subseq_as_collection = 'CollectionWithEquatableElement.SubSequence : Collection,'
-    else:
-      subseq_as_collection=''
     return '''
     C : %(protocol)s,
     CollectionWithEquatableElement : %(protocol)s,
-    %(subseq_as_collection)s
-    C.SubSequence : %(protocol)s,
-    C.Indices : %(protocol)s,
     CollectionWithEquatableElement.Iterator.Element : Equatable
   ''' % locals()
 

stdlib/private/StdlibCollectionUnittest/CheckMutableCollectionType.swift.gyb

@@ -121,8 +121,6 @@ extension TestSuite {
     isFixedLengthCollection: Bool,
     collectionIsBidirectional: Bool = false
   ) where
-    C.SubSequence : MutableCollection,
-    C.Indices : Collection,
     CollectionWithEquatableElement.Iterator.Element : Equatable,
     CollectionWithComparableElement.Iterator.Element : Comparable {
 
@@ -776,8 +774,6 @@ self.test("\(testNamePrefix).partition/InvalidOrderings") {
     withUnsafeMutableBufferPointerIsSupported: Bool,
     isFixedLengthCollection: Bool
   ) where
-    C.SubSequence : BidirectionalCollection & MutableCollection,
-    C.Indices : BidirectionalCollection,
     CollectionWithEquatableElement.Iterator.Element : Equatable,
     CollectionWithComparableElement.Iterator.Element : Comparable {
 
@@ -922,8 +918,6 @@ self.test("\(testNamePrefix).partition/DispatchesThrough_withUnsafeMutableBuffer
     withUnsafeMutableBufferPointerIsSupported: Bool,
     isFixedLengthCollection: Bool
   ) where
-    C.SubSequence : RandomAccessCollection & MutableCollection,
-    C.Indices : RandomAccessCollection,
     CollectionWithEquatableElement.Iterator.Element : Equatable,
     CollectionWithComparableElement.Iterator.Element : Comparable {
 

stdlib/private/StdlibCollectionUnittest/CheckRangeReplaceableCollectionType.swift

@@ -462,10 +462,7 @@ extension TestSuite {
     outOfBoundsIndexOffset: Int = 1,
     collectionIsBidirectional: Bool = false
   ) where
-    C.SubSequence : Collection,
-    C.Indices : Collection,
-    CollectionWithEquatableElement.Iterator.Element : Equatable,
-    CollectionWithEquatableElement.SubSequence : Collection {
+    CollectionWithEquatableElement.Iterator.Element : Equatable {
 
     var testNamePrefix = testNamePrefix
 
@@ -1180,8 +1177,6 @@ self.test("\(testNamePrefix).OperatorPlus") {
     resiliencyChecks: CollectionMisuseResiliencyChecks = .all,
     outOfBoundsIndexOffset: Int = 1
   ) where
-    C.SubSequence : BidirectionalCollection & RangeReplaceableCollection,
-    C.Indices : BidirectionalCollection,
     CollectionWithEquatableElement.Iterator.Element : Equatable {
 
     var testNamePrefix = testNamePrefix
@@ -1302,8 +1297,6 @@ self.test("\(testNamePrefix).removeLast(n: Int)/whereIndexIsBidirectional/remove
     resiliencyChecks: CollectionMisuseResiliencyChecks = .all,
     outOfBoundsIndexOffset: Int = 1
   ) where
-    C.SubSequence : RandomAccessCollection & RangeReplaceableCollection,
-    C.Indices : RandomAccessCollection,
     CollectionWithEquatableElement.Iterator.Element : Equatable {
 
     var testNamePrefix = testNamePrefix

stdlib/private/StdlibCollectionUnittest/CheckRangeReplaceableSliceType.swift

@@ -33,7 +33,6 @@ extension TestSuite {
     collectionIsBidirectional: Bool = false
   ) where
     C.SubSequence == C,
-    C.Indices : Collection,
     CollectionWithEquatableElement.SubSequence == CollectionWithEquatableElement,
     CollectionWithEquatableElement.Iterator.Element : Equatable {
 
@@ -165,7 +164,6 @@ extension TestSuite {
     outOfBoundsIndexOffset: Int = 1
   ) where
     C.SubSequence == C,
-    C.Indices : BidirectionalCollection,
     CollectionWithEquatableElement.SubSequence == CollectionWithEquatableElement,
     CollectionWithEquatableElement.Iterator.Element : Equatable {
 
@@ -310,7 +308,6 @@ extension TestSuite {
     outOfBoundsIndexOffset: Int = 1
   ) where
     C.SubSequence == C,
-    C.Indices : RandomAccessCollection,
     CollectionWithEquatableElement.SubSequence == CollectionWithEquatableElement,
     CollectionWithEquatableElement.Iterator.Element : Equatable {
 

stdlib/private/StdlibCollectionUnittest/CheckSequenceType.swift

@@ -1536,13 +1536,7 @@ extension TestSuite {
 
     resiliencyChecks: CollectionMisuseResiliencyChecks = .all
   ) where
-    SequenceWithEquatableElement.Iterator.Element : Equatable,
-    SequenceWithEquatableElement.SubSequence : Sequence,
-    SequenceWithEquatableElement.SubSequence.Iterator.Element
-      == SequenceWithEquatableElement.Iterator.Element,
-    S.SubSequence : Sequence,
-    S.SubSequence.Iterator.Element == S.Iterator.Element,
-    S.SubSequence.SubSequence == S.SubSequence {
+    SequenceWithEquatableElement.Iterator.Element : Equatable {
 
     var testNamePrefix = testNamePrefix
 

stdlib/private/StdlibUnittest/StdlibUnittest.swift.gyb

@@ -378,25 +378,14 @@ public func expectTrapping<Bound>(
 public func expectType<T>(_: T.Type, _ x: inout T) {}
 public func expectEqualType<T>(_: T.Type, _: T.Type) {}
 
-public func expectSequenceType<X : Sequence>(_ x: X) -> X
-  where
-  X.SubSequence : Sequence,
-  X.SubSequence.Iterator.Element == X.Iterator.Element,
-  X.SubSequence.SubSequence == X.SubSequence {
+public func expectSequenceType<X : Sequence>(_ x: X) -> X {
   return x
 }
 
 % for Mutable in ['', 'Mutable']:
 public func expect${Mutable}CollectionType<X : ${Mutable}Collection>(
   _ x: X.Type
-) where
-  // FIXME(ABI)#2 (Associated Types with where clauses): there should be no constraints in
-  // the 'where' clause, all of these should be required by the protocol.
-%   if Mutable == '':
-  X.SubSequence : Collection,
-%   end
-  // X.SubSequence.Indices == X.Indices, // FIXME(ABI)#3 (Recursive Protocol Constraints): can't have this constraint now.
-  X.Indices : Collection {}
+) {}
 % end
 
 /// A slice is a `Collection` that when sliced returns an instance of
@@ -417,13 +406,7 @@ public func expectSequenceAssociatedTypes<X : Sequence>(
   sequenceType: X.Type,
   iteratorType: X.Iterator.Type,
   subSequenceType: X.SubSequence.Type
-) where
-  // FIXME(ABI)#4 (Associated Types with where clauses): there should be no constraints in
-  // the 'where' clause, all of these should be required by the protocol.
-  X.SubSequence : Sequence,
-  X.SubSequence.Iterator.Element == X.Iterator.Element,
-  // X.SubSequence.Indices == X.Indices, // FIXME(ABI)#5 (Recursive Protocol Constraints): can't have this constraint now.
-  X.SubSequence.SubSequence == X.SubSequence {}
+) {}
 
 /// Check that all associated types of a `Collection` are what we expect them
 /// to be.
@@ -434,12 +417,7 @@ public func expectCollectionAssociatedTypes<X : Collection>(
   indexType: X.Index.Type,
   indexDistanceType: X.IndexDistance.Type,
   indicesType: X.Indices.Type
-) where
-  // FIXME(ABI)#6 (Associated Types with where clauses): there should be no constraints in
-  // the 'where' clause, all of these should be required by the protocol.
-  X.SubSequence : Collection,
-  // X.SubSequence.Indices == X.Indices, // FIXME(ABI)#7 (Recursive Protocol Constraints): can't have this constraint now.
-  X.Indices : Collection {}
+) {}
 
 /// Check that all associated types of a `BidirectionalCollection` are what we
 /// expect them to be.
@@ -450,12 +428,7 @@ public func expectBidirectionalCollectionAssociatedTypes<X : BidirectionalCollec
   indexType: X.Index.Type,
   indexDistanceType: X.IndexDistance.Type,
   indicesType: X.Indices.Type
-) where
-  // FIXME(ABI)#8 (Associated Types with where clauses): there should be no constraints in
-  // the 'where' clause, all of these should be required by the protocol.
-  X.SubSequence : BidirectionalCollection,
-  // X.SubSequence.Indices == X.Indices, // FIXME(ABI)#9 (Recursive Protocol Constraints): can't have this constraint now.
-  X.Indices : BidirectionalCollection {}
+) {}
 
 /// Check that all associated types of a `RandomAccessCollection` are what we
 /// expect them to be.
@@ -466,12 +439,7 @@ public func expectRandomAccessCollectionAssociatedTypes<X : RandomAccessCollecti
   indexType: X.Index.Type,
   indexDistanceType: X.IndexDistance.Type,
   indicesType: X.Indices.Type
-) where
-  // FIXME(ABI)#10 (Associated Types with where clauses): there should be no constraints in
-  // the 'where' clause, all of these should be required by the protocol.
-  X.SubSequence : RandomAccessCollection,
-  // X.SubSequence.Indices == X.Indices, // FIXME(ABI)#11 (Recursive Protocol Constraints): can't have this constraint now.
-  X.Indices : RandomAccessCollection {}
+) {}
 
 public struct AssertionResult : CustomStringConvertible {
   init(isPass: Bool) {

stdlib/public/SDK/Dispatch/Data.swift

@@ -299,6 +299,7 @@ public struct DispatchData : RandomAccessCollection, _ObjectiveCBridgeable {
 }
 
 public struct DispatchDataIterator : IteratorProtocol, Sequence {
+  public typealias Element = UInt8
 
 	/// Create an iterator over the given DispatchData
 	public init(_data: DispatchData) {

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/ArrayBufferProtocol.swift

@@ -16,10 +16,7 @@
 internal protocol _ArrayBufferProtocol
   : MutableCollection, RandomAccessCollection {
 
-  associatedtype Indices 
-  // FIXME(ABI) (Revert Where Clauses): Remove this conformance
-  : RandomAccessCollection 
-    = CountableRange<Int>
+  associatedtype Indices = CountableRange<Int>
 
   /// Create an empty buffer.
   init()