Revert "Merge pull request swiftlang#9379 from airspeedswift/redundant-where"

95e9681

Author: airspeedswift

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/Collection.swift

@@ -648,7 +648,8 @@ public struct IndexingIterator<
 /// an O(*n*) operation.
 public protocol Collection : _Indexable, Sequence 
 where SubSequence: Collection, Indices: Collection,
-      SubSequence.Index == Index
+      SubSequence.Index == Index, 
+      SubSequence.Iterator.Element == Iterator.Element 
 {
   /// A type that represents the number of steps between a pair of
   /// indices.