Remove collection conformances to Equatable and Hashable (#124)

Author: Tim Vermeulen

Guides/Compacted.md

@@ -31,8 +31,8 @@ extension Collection {
 ```
 
 One is a more general `CompactedSequence` for any `Sequence` base. And the other a more specialized `CompactedCollection` 
-where base is a `Collection` and with conditional conformance to `BidirectionalCollection`, `RandomAccessCollection`, 
-`LazyCollectionProtocol`, `Equatable` and `Hashable` when base collection conforms to them.
+where base is a `Collection` and with conditional conformance to `BidirectionalCollection`, `RandomAccessCollection` and
+`LazyCollectionProtocol` when base collection conforms to them.
 
 ### Naming
 

Sources/Algorithms/Chain.swift

@@ -283,9 +283,6 @@ extension Chain2: BidirectionalCollection
 extension Chain2: RandomAccessCollection
   where Base1: RandomAccessCollection, Base2: RandomAccessCollection {}
 
-extension Chain2: Equatable where Base1: Equatable, Base2: Equatable {}
-extension Chain2: Hashable where Base1: Hashable, Base2: Hashable {}
-
 //===----------------------------------------------------------------------===//
 // chain(_:_:)
 //===----------------------------------------------------------------------===//

Sources/Algorithms/Chunked.swift

@@ -512,21 +512,6 @@ extension Collection {
   }
 }
 
-// Conditional conformances.
-extension ChunkedByCount: Equatable where Base: Equatable {}
-
-// Since we have another stored property of type `Index` on the
-// collection, synthesis of `Hashble` conformace would require
-// a `Base.Index: Hashable` constraint, so we implement the hasher
-// only in terms of `base` and `chunkCount`. Since the computed
-// index is based on it, it should not make a difference here.
-extension ChunkedByCount: Hashable where Base: Hashable {
-  @inlinable
-  public func hash(into hasher: inout Hasher) {
-    hasher.combine(base)
-    hasher.combine(chunkCount)
-  }
-}
 extension ChunkedByCount.Index: Hashable where Base.Index: Hashable {}
 
 // Lazy conditional conformance.

Sources/Algorithms/Combinations.swift

@@ -181,8 +181,6 @@ extension Combinations: Sequence {
 }
 
 extension Combinations: LazySequenceProtocol where Base: LazySequenceProtocol {}
-extension Combinations: Equatable where Base: Equatable {}
-extension Combinations: Hashable where Base: Hashable {}
 
 //===----------------------------------------------------------------------===//
 // combinations(ofCount:)

Sources/Algorithms/Compacted.swift

@@ -179,48 +179,3 @@ extension CompactedCollection: LazySequenceProtocol
   where Base: LazySequenceProtocol {}
 extension CompactedCollection: LazyCollectionProtocol
   where Base: LazyCollectionProtocol {}
-
-
-// Hashable and Equatable conformance are based on each non-nil
-// element on base collection.
-extension CompactedSequence: Equatable
-  where Base.Element: Equatable {
-
-  @inlinable
-  public static func ==(lhs: CompactedSequence,
-                        rhs: CompactedSequence) -> Bool {
-    lhs.elementsEqual(rhs)
-  }
-}
-
-extension CompactedSequence: Hashable
-  where Element: Hashable {
-
-  @inlinable
-  public func hash(into hasher: inout Hasher) {
-    for element in self {
-      hasher.combine(element)
-    }
-  }
-}
-
-extension CompactedCollection: Equatable
-  where Base.Element: Equatable {
-
-  @inlinable
-  public static func ==(lhs: CompactedCollection,
-                        rhs: CompactedCollection) -> Bool {
-    lhs.elementsEqual(rhs)
-  }
-}
-
-extension CompactedCollection: Hashable
-  where Element: Hashable {
-
-  @inlinable
-  public func hash(into hasher: inout Hasher) {
-    for element in self {
-      hasher.combine(element)
-    }
-  }
-}

Sources/Algorithms/Cycle.swift

@@ -163,9 +163,6 @@ extension FiniteCycle: BidirectionalCollection
 extension FiniteCycle: RandomAccessCollection
   where Base: RandomAccessCollection {}
 
-extension FiniteCycle: Equatable where Base: Equatable {}
-extension FiniteCycle: Hashable where Base: Hashable {}
-
 //===----------------------------------------------------------------------===//
 // cycled()
 //===----------------------------------------------------------------------===//

Sources/Algorithms/Indexed.swift

@@ -72,8 +72,6 @@ extension Indexed: BidirectionalCollection where Base: BidirectionalCollection {
 extension Indexed: RandomAccessCollection where Base: RandomAccessCollection {}
 extension Indexed: LazySequenceProtocol where Base: LazySequenceProtocol {}
 extension Indexed: LazyCollectionProtocol where Base: LazyCollectionProtocol {}
-extension Indexed: Equatable where Base: Equatable {}
-extension Indexed: Hashable where Base: Hashable {}
 
 //===----------------------------------------------------------------------===//
 // indexed()

Sources/Algorithms/Product.swift

@@ -438,8 +438,6 @@ extension Product2: RandomAccessCollection
   where Base1: RandomAccessCollection, Base2: RandomAccessCollection {}
 
 extension Product2.Index: Hashable where Base1.Index: Hashable, Base2.Index: Hashable {}
-extension Product2: Equatable where Base1: Equatable, Base2: Equatable {}
-extension Product2: Hashable where Base1: Hashable, Base2: Hashable {}
 
 //===----------------------------------------------------------------------===//
 // product(_:_:)

Sources/Algorithms/Stride.swift

@@ -269,22 +269,4 @@ extension StrideCollection: BidirectionalCollection
 }
 
 extension StrideCollection: RandomAccessCollection where Base: RandomAccessCollection {}
-
-extension StrideCollection: Equatable where Base.Element: Equatable {
-  @inlinable
-  public static func == (lhs: StrideCollection, rhs: StrideCollection) -> Bool {
-    lhs.elementsEqual(rhs, by: ==)
-  }
-}
-
-extension StrideCollection: Hashable where Base.Element: Hashable {
-  @inlinable
-  public func hash(into hasher: inout Hasher) {
-    hasher.combine(stride)
-    for element in self {
-      hasher.combine(element)
-    }
-  }
-}
-
 extension StrideCollection.Index: Hashable where Base.Index: Hashable {}

Sources/Algorithms/Windows.swift

@@ -350,6 +350,4 @@ extension Windows: BidirectionalCollection where Base: BidirectionalCollection {
 extension Windows: LazySequenceProtocol where Base: LazySequenceProtocol {}
 extension Windows: LazyCollectionProtocol where Base: LazyCollectionProtocol {}
 extension Windows: RandomAccessCollection where Base: RandomAccessCollection {}
-extension Windows: Equatable where Base: Equatable {}
-extension Windows: Hashable where Base: Hashable, Base.Index: Hashable {}
 extension Windows.Index: Hashable where Base.Index: Hashable {}

Tests/SwiftAlgorithmsTests/ChunkedTests.swift

@@ -145,16 +145,4 @@ final class ChunkedTests: XCTestCase {
       validateIndexTraversals(chunks)
     }
   }
-  
-  func testChunksOfCountHash() {
-    let collection1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
-    let collection2 = [1, 2, 3, 4, 5]
-    
-    XCTAssertEqualHashValue(
-      collection1.chunks(ofCount: 1), collection1.chunks(ofCount: 1))
-    XCTAssertNotEqualHashValue(
-      collection1.chunks(ofCount: 1), collection2.chunks(ofCount: 1))
-    XCTAssertNotEqualHashValue(
-      collection1.chunks(ofCount: 2), collection2.chunks(ofCount: 4))
-  }
 }

Tests/SwiftAlgorithmsTests/CompactedTests.swift

@@ -41,41 +41,4 @@ final class CompactedTests: XCTestCase {
       validateIndexTraversals(array.compacted())
     }
   }
-
-  func testCollectionEquatableConformances() {
-    for array in self.tests {
-      XCTAssertEqual(
-        array.eraseToAnyHashableSequence().compacted(),
-        array.compactMap({ $0 }).eraseToAnyHashableSequence().compacted()
-      )
-      XCTAssertEqual(
-        array.compacted(), array.compactMap({ $0 }).compacted()
-      )
-    }
-  }
-  
-  func testCollectionHashableConformances() {
-    for array1 in self.tests {
-      for array2 in self.tests {
-        // For non-equal Collections and Sequences that produce the same
-        // compacted, the compacted wrapper should produce the same hash.
-        // e.g. [1, 2, 3, nil, nil, 4].compacted() should produce the
-        // same hash as [1, nil, 2, nil, 3, 4].compacted()
-        guard !array1.elementsEqual(array2) &&
-               array1.compacted() == array2.compacted() else {
-          continue
-        }
-        
-        let seq = array1.eraseToAnyHashableSequence()
-        let seq2 = array2.eraseToAnyHashableSequence()
-        
-        XCTAssertEqualHashValue(
-          seq.compacted(), seq2.compacted()
-        )
-        XCTAssertEqualHashValue(
-          array1.compacted(), array2.compacted()
-        )
-      }
-    }
-  }
 }

Tests/SwiftAlgorithmsTests/StrideTests.swift

@@ -64,19 +64,6 @@ final class StridingTests: XCTestCase {
 //    a.index(after: a.endIndex) // Precondition failed: Advancing past end index
   }
 
-  func testStrideCompositionEquivalence() {
-    let a = (0...10)
-    XCTAssertEqualSequences(a.striding(by: 6), a.striding(by: 2).striding(by: 3))
-    XCTAssertTrue(a.striding(by: 6) == a.striding(by: 2).striding(by: 3))
-    XCTAssert(type(of: a.striding(by: 2).striding(by: 3)) == StrideCollection<ClosedRange<Int>>.self)
-  }
-  
-  func testEquality() {
-    let a = [1, 2, 3, 4, 5].striding(by: 2)
-    let b = [1, 0, 3, 0, 5].striding(by: 2)
-    XCTAssertEqual(a, b)
-  }
-  
   func testStrideLast() {
     XCTAssertEqual((1...10).striding(by: 2).last, 9) // 1, 3, 5, 7, 9
     XCTAssertEqual((1...10).striding(by: 3).last, 10) // 1, 4, 7, 10

Tests/SwiftAlgorithmsTests/TestUtilities.swift

@@ -46,27 +46,6 @@ struct SplitMix64: RandomNumberGenerator {
   }
 }
 
-// An eraser helper to any hashable sequence.
-struct AnyHashableSequence<Base>
-  where Base: Sequence, Base: Hashable {
-  var base: Base
-}
-
-extension AnyHashableSequence: Hashable {}
-extension AnyHashableSequence: Sequence {
-  typealias Iterator = Base.Iterator
-  
-  func makeIterator() -> Iterator {
-    base.makeIterator()
-  }
-}
-
-extension Sequence where Self: Hashable {
-  func eraseToAnyHashableSequence() -> AnyHashableSequence<Self> {
-    AnyHashableSequence(base: self)
-  }
-}
-
 // An eraser helper to any mutable collection
 struct AnyMutableCollection<Base> where Base: MutableCollection {
   var base: Base
@@ -184,38 +163,6 @@ func XCTAssertEqualCollections<C1: Collection, C2: Collection>(
   }
 }
 
-func hash<T: Hashable>(_ value: T) -> Int {
-  var hasher = Hasher()
-  value.hash(into: &hasher)
-  return hasher.finalize()
-}
-
-/// Asserts that two hashable instances produce the same hash value.
-func XCTAssertEqualHashValue<T: Hashable, U: Hashable>(
-  _ expression1: @autoclosure () throws -> T,
-  _ expression2: @autoclosure () throws -> U,
-  _ message: @autoclosure () -> String = "",
-  file: StaticString = #file, line: UInt = #line
-) {
-  XCTAssertEqual(
-    hash(try expression1()), hash(try expression2()),
-    message(), file: file, line: line
-  )
-}
-
-/// Asserts that two hashable instances don't produce the same hash value.
-func XCTAssertNotEqualHashValue<T: Hashable, U: Hashable>(
-  _ expression1: @autoclosure () throws -> T,
-  _ expression2: @autoclosure () throws -> U,
-  _ message: @autoclosure () -> String = "",
-  file: StaticString = #file, line: UInt = #line
-) {
-  XCTAssertNotEqual(
-    hash(try expression1()), hash(try expression2()),
-    message(), file: file, line: line
-  )
-}
-
 /// Tests that all index traversal methods behave as expected.
 ///
 /// Verifies the correctness of the implementations of `startIndex`, `endIndex`,