Merge pull request swiftlang#9512 from airspeedswift/come-back-where-…

…clauses-we-miss-you

[stdlib] Revert addition of some recursive where clauses on Collection protocols

stdlib/private/StdlibCollectionUnittest/CheckCollectionInstance.swift.gyb

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

stdlib/private/StdlibCollectionUnittest/CheckCollectionType.swift.gyb

@@ -471,9 +471,16 @@ 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()
 
@@ -487,7 +494,6 @@ internal enum _SubSequenceSubscriptOnRangeMode {
       [CollectionWithEquatableElement.Iterator.Element]
     ) -> CollectionWithEquatableElement,
 
-
     wrapValueIntoEquatable: @escaping (
       MinimalEquatableValue) -> CollectionWithEquatableElement.Iterator.Element,
 

stdlib/private/StdlibCollectionUnittest/CheckMutableCollectionType.swift.gyb

@@ -121,6 +121,8 @@ extension TestSuite {
     isFixedLengthCollection: Bool,
     collectionIsBidirectional: Bool = false
   ) where
+    C.SubSequence : MutableCollection,
+    C.Indices : Collection,
     CollectionWithEquatableElement.Iterator.Element : Equatable,
     CollectionWithComparableElement.Iterator.Element : Comparable {
 
@@ -781,6 +783,8 @@ 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 {
 
@@ -925,6 +929,8 @@ 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

@@ -462,7 +462,10 @@ extension TestSuite {
     outOfBoundsIndexOffset: Int = 1,
     collectionIsBidirectional: Bool = false
   ) where
-    CollectionWithEquatableElement.Iterator.Element : Equatable {
+    C.SubSequence : Collection,
+    C.Indices : Collection,
+    CollectionWithEquatableElement.Iterator.Element : Equatable,
+    CollectionWithEquatableElement.SubSequence : Collection {
 
     var testNamePrefix = testNamePrefix
 
@@ -1177,6 +1180,8 @@ 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
@@ -1297,6 +1302,8 @@ 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

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

stdlib/private/StdlibUnittest/StdlibUnittest.swift.gyb

@@ -376,7 +376,14 @@ public func expectSequenceType<X : Sequence>(_ x: X) -> 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
@@ -414,7 +421,12 @@ 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.
@@ -425,7 +437,12 @@ 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.
@@ -436,7 +453,12 @@ 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/core/ArrayBufferProtocol.swift

@@ -16,7 +16,10 @@
 internal protocol _ArrayBufferProtocol
   : MutableCollection, RandomAccessCollection {
 
-  associatedtype Indices = CountableRange<Int>
+  associatedtype Indices 
+  // FIXME(ABI) (Revert Where Clauses): Remove this conformance
+  : RandomAccessCollection 
+    = CountableRange<Int>
 
   /// The type of elements stored in the buffer.
   associatedtype Element

stdlib/public/core/BidirectionalCollection.swift

@@ -66,7 +66,9 @@ public protocol _BidirectionalIndexable : _Indexable {
 /// - If `i > c.startIndex && i <= c.endIndex`
 ///   `c.index(after: c.index(before: i)) == i`.
 public protocol BidirectionalCollection : _BidirectionalIndexable, Collection 
-where SubSequence: BidirectionalCollection, Indices: BidirectionalCollection {
+// FIXME(ABI) (Revert Where Clauses): Restore these 
+// where SubSequence: BidirectionalCollection, Indices: BidirectionalCollection
+{
 
 // TODO: swift-3-indexing-model - replaces functionality in BidirectionalIndex
   /// Returns the position immediately before the given index.
@@ -84,11 +86,17 @@ where SubSequence: BidirectionalCollection, Indices: BidirectionalCollection {
 
   /// A sequence that can represent a contiguous subrange of the collection's
   /// elements.
-  associatedtype SubSequence = BidirectionalSlice<Self>
+  associatedtype SubSequence
+  // FIXME(ABI) (Revert Where Clauses): Remove these conformances
+  : _BidirectionalIndexable, Collection
+    = BidirectionalSlice<Self>
 
   /// A type that represents the indices that are valid for subscripting the
   /// collection, in ascending order.
-  associatedtype Indices = DefaultBidirectionalIndices<Self>
+  associatedtype Indices 
+  // FIXME(ABI) (Revert Where Clauses): Remove these conformances
+  : _BidirectionalIndexable, Collection
+    = DefaultBidirectionalIndices<Self>
 
   /// The indices that are valid for subscripting the collection, in ascending
   /// order.

stdlib/public/core/Collection.swift

@@ -647,8 +647,8 @@ public struct IndexingIterator<
 /// count the number of contained elements, accessing its `count` property is
 /// an O(*n*) operation.
 public protocol Collection : _Indexable, Sequence 
-where SubSequence: Collection, Indices: Collection,
-      SubSequence.Index == Index
+// FIXME(ABI) (Revert Where Clauses): Restore these 
+// where SubSequence: Collection, Indices: Collection,
 {
   /// A type that represents the number of steps between a pair of
   /// indices.
@@ -675,9 +675,15 @@ where SubSequence: Collection, Indices: Collection,
   /// This associated type appears as a requirement in the `Sequence`
   /// protocol, but it is restated here with stricter constraints. In a
   /// collection, the subsequence should also conform to `Collection`.
-  associatedtype SubSequence = Slice<Self>
-      where Iterator.Element == SubSequence.Iterator.Element,
-            SubSequence.SubSequence == SubSequence
+  associatedtype SubSequence
+  // FIXME(ABI) (Revert Where Clauses): remove these conformances:
+  : _IndexableBase, Sequence
+     = Slice<Self>
+      where SubSequence.SubSequence == SubSequence
+  // FIXME(ABI) (Revert Where Clauses): and this where clause:
+          , Iterator.Element == SubSequence.Iterator.Element
+          , SubSequence.Index == Index
+
 
   // FIXME(ABI)#98 (Recursive Protocol Constraints):
   // FIXME(ABI)#99 (Associated Types with where clauses):
@@ -739,10 +745,15 @@ where SubSequence: Collection, Indices: Collection,
 
   /// A type that represents the indices that are valid for subscripting the
   /// collection, in ascending order.
-  associatedtype Indices = DefaultIndices<Self>
-    where Indices.Iterator.Element == Index,
+  associatedtype Indices
+  // FIXME(ABI) (Revert Where Clauses): Remove these two conformances 
+  : _Indexable, Sequence
+    = DefaultIndices<Self>
+    where Indices.Iterator.Element == Index, 
           Indices.Index == Index
-
+  // FIXME(ABI) (Revert Where Clauses): Remove this where clause
+        , Indices.SubSequence == Indices
+
   // FIXME(ABI)#100 (Recursive Protocol Constraints):
   // associatedtype Indices : Collection
   //   where

stdlib/public/core/ExistentialCollection.swift.gyb

@@ -423,14 +423,21 @@ internal class _AnyRandomAccessCollectionBox<Element>
 %     assert False, 'Unknown kind'
 %   end
 
+
+
 @_fixed_layout
 @_versioned
 internal final class _${Kind}Box<S : ${Kind}> : _Any${Kind}Box<S.Iterator.Element>
-%  if Kind == 'Sequence':
   where
   S.SubSequence : ${Kind},
+// FIXME(ABI) (Revert Where Clauses): apply all this only to Sequence:
+%  if Kind == 'Sequence':
   S.SubSequence.Iterator.Element == S.Iterator.Element,
   S.SubSequence.SubSequence == S.SubSequence
+// FIXME(ABI) (Revert Where Clauses): remove this else clause:
+%  else:
+  S.SubSequence.Indices : ${Kind},
+  S.Indices : ${Kind}
 %  end
 {
   internal typealias Element = S.Iterator.Element
@@ -1035,8 +1042,12 @@ public struct ${Self}<Element>
   @_inlineable
   public init<C : ${SubProtocol}>(_ base: C)
     where
-    // FIXME(ABI)#101 (Associated Types with where clauses): these constraints should be applied to
-    // associated types of Collection.
+    // FIXME(ABI) (Revert Where Clauses): remove next 3 lines
+    C.SubSequence : ${SubProtocol},
+    C.SubSequence.Indices : ${SubProtocol},
+    C.Indices : ${SubProtocol},
+    // FIXME(ABI)#101 (Associated Types with where clauses): these constraints
+    // should be applied to associated types of Collection.
     C.SubSequence.Iterator.Element == Element
      {
     // Traversal: ${Traversal}

stdlib/public/core/Mirror.swift

@@ -214,7 +214,10 @@ public struct Mirror {
     children: C,
     displayStyle: DisplayStyle? = nil,
     ancestorRepresentation: AncestorRepresentation = .generated
-  ) where C.Iterator.Element == Child {
+  ) where C.Iterator.Element == Child 
+  // FIXME(ABI) (Revert Where Clauses): Remove these 
+  , C.SubSequence : Collection, C.SubSequence.Indices : Collection, C.Indices : Collection
+  {
 
     self.subjectType = Subject.self
     self._makeSuperclassMirror = Mirror._superclassIterator(
@@ -261,7 +264,10 @@ public struct Mirror {
     unlabeledChildren: C,
     displayStyle: DisplayStyle? = nil,
     ancestorRepresentation: AncestorRepresentation = .generated
-  ) {
+  ) 
+  // FIXME(ABI) (Revert Where Clauses): Remove these two clauses
+  where C.SubSequence : Collection, C.Indices : Collection
+  {
 
     self.subjectType = Subject.self
     self._makeSuperclassMirror = Mirror._superclassIterator(

stdlib/public/core/MutableCollection.swift

@@ -197,8 +197,13 @@ public protocol _MutableIndexable : _Indexable {
 ///     a[i] = x
 ///     let y = x
 public protocol MutableCollection : _MutableIndexable, Collection
-where SubSequence: MutableCollection {
-  associatedtype SubSequence = MutableSlice<Self>
+// FIXME(ABI) (Revert Where Clauses): restore this:
+// where SubSequence: MutableCollection
+{
+  associatedtype SubSequence
+  // FIXME(ABI) (Revert Where Clauses): remove this conformance:
+  : Collection
+   = MutableSlice<Self>
 
   /// Accesses the element at the specified position.
   ///

stdlib/public/core/RandomAccessCollection.swift

@@ -48,15 +48,22 @@ public protocol _RandomAccessIndexable : _BidirectionalIndexable {
 /// `distance(from:to:)` methods with O(1) efficiency.
 public protocol RandomAccessCollection :
   _RandomAccessIndexable, BidirectionalCollection
-  where SubSequence: RandomAccessCollection, Indices: RandomAccessCollection
+// FIXME(ABI) (Revert Where Clauses): Restore this:
+// where SubSequence: RandomAccessCollection, Indices: RandomAccessCollection
 {
   /// A collection that represents a contiguous subrange of the collection's
   /// elements.
-  associatedtype SubSequence = RandomAccessSlice<Self>
+  associatedtype SubSequence
+  // FIXME(ABI) (Revert Where Clauses): Remove these two constraints:
+   : _RandomAccessIndexable, BidirectionalCollection
+   = RandomAccessSlice<Self>
 
   /// A type that represents the indices that are valid for subscripting the
   /// collection, in ascending order.
-  associatedtype Indices = DefaultRandomAccessIndices<Self>
+  associatedtype Indices 
+  // FIXME(ABI) (Revert Where Clauses): Remove these two constraints:
+  : _RandomAccessIndexable, BidirectionalCollection
+  = DefaultRandomAccessIndices<Self>
 
   /// The indices that are valid for subscripting the collection, in ascending
   /// order.