Arrays.swift.gyb

// RUN: %empty-directory(%t)
//
// RUN: %gyb %s -o %t/main.swift
// RUN: if [ %target-runtime == "objc" ]; then \
// RUN:   %target-clang -fobjc-arc %S/Inputs/SlurpFastEnumeration/SlurpFastEnumeration.m -c -o %t/SlurpFastEnumeration.o; \
// RUN:   %line-directive %t/main.swift -- %target-build-swift %t/main.swift %S/Inputs/ArrayTypesAndHelpers.swift -I %S/Inputs/SlurpFastEnumeration/ -Xlinker %t/SlurpFastEnumeration.o -o %t/Arrays -Xfrontend -disable-access-control; \
// RUN: else \
// RUN:   %line-directive %t/main.swift -- %target-build-swift %S/Inputs/ArrayTypesAndHelpers.swift %t/main.swift -o %t/Arrays -Xfrontend -disable-access-control; \
// RUN: fi
//
// RUN: %line-directive %t/main.swift -- %target-run %t/Arrays
// REQUIRES: executable_test

import Swift
import StdlibUnittest
import StdlibCollectionUnittest

#if _runtime(_ObjC)
import Foundation
import StdlibUnittestFoundationExtras
#endif

let CopyToNativeArrayBufferTests = TestSuite("CopyToNativeArrayBufferTests")

extension Array {
  func _rawIdentifier() -> Int {
    return unsafeBitCast(self, to: Int.self)
  }
}

CopyToNativeArrayBufferTests.test("Sequence._copyToContiguousArray()") {
  do {
    // Call from a static context.
    let s =
      MinimalSequence(elements: LifetimeTracked(10)..<LifetimeTracked(27))

    expectEqual(0, s.timesMakeIteratorCalled.value)
    let copy = s._copyToContiguousArray()
    expectEqual(1, s.timesMakeIteratorCalled.value)
    expectEqualSequence(
      Array(10..<27),
      copy.map { $0.value })
  }
  do {
    // Call from a generic context.
    let wrapped = MinimalSequence(elements: LifetimeTracked(10)..<LifetimeTracked(27))
    let s = LoggingSequence(wrapping: wrapped)

    expectEqual(0, wrapped.timesMakeIteratorCalled.value)
    let copy = s._copyToContiguousArray()
    expectEqual(1, wrapped.timesMakeIteratorCalled.value)
    expectEqualSequence(
      Array(10..<27),
      copy.map { $0.value })
  }
}

CopyToNativeArrayBufferTests.test("Collection._copyToContiguousArray()") {
  // Check that collections are handled with the collection-specific API.  This
  // means that we are calling the right default implementation (one for
  // collections, not the one for sequences).

  do {
    // Call from a static context.
    let c =
      DefaultedCollection(elements: LifetimeTracked(10)..<LifetimeTracked(27))

    expectEqual(0, c.timesMakeIteratorCalled.value)
    expectEqual(0, c.timesStartIndexCalled.value)
    let copy = c._copyToContiguousArray()
    expectEqual(0, c.timesMakeIteratorCalled.value)
    expectNotEqual(0, c.timesStartIndexCalled.value)
    expectEqualSequence(
      Array(10..<27),
      copy.map { $0.value })
  }
  do {
    // Call from a generic context.
    let wrapped =
      DefaultedCollection(elements: LifetimeTracked(10)..<LifetimeTracked(27))
    let s = LoggingSequence(wrapping: wrapped)
    expectEqual(0, wrapped.timesMakeIteratorCalled.value)
    expectEqual(0, wrapped.timesStartIndexCalled.value)
    let copy = s._copyToContiguousArray()
    expectEqual(0, wrapped.timesMakeIteratorCalled.value)
    expectNotEqual(0, wrapped.timesStartIndexCalled.value)

    expectEqualSequence(
      Array(10..<27),
      copy.map { $0.value })
  }
}

%{
all_array_types = ['ContiguousArray', 'ArraySlice', 'Array']
}%

var ArrayTestSuite = TestSuite("Array")

ArrayTestSuite.test("sizeof") {
  var a = [ 10, 20, 30 ]
#if arch(i386) || arch(arm)
  expectEqual(4, MemoryLayout.size(ofValue: a))
#else
  expectEqual(8, MemoryLayout.size(ofValue: a))
#endif
}

ArrayTestSuite.test("valueDestruction") {
  var a = [LifetimeTracked]()
  for i in 100...110 {
    a.append(LifetimeTracked(i))
  }
}

ArrayTestSuite.test("capacity/reserveCapacity(_:)") {
  var a1 = [1010, 1020, 1030]
  expectGE(a1.capacity, 3)
  a1.append(1040)
  expectGT(a1.capacity, 3)

  // Reserving new capacity jumps up to next limit.
  a1.reserveCapacity(7)
  expectGE(a1.capacity, 7)

  // Can reserve right up to a limit.
  a1.reserveCapacity(24)
  expectGE(a1.capacity, 24)

  // Fill up to the limit, no reallocation.
  for v in stride(from: 50, through: 240, by: 10).lazy.map({ 1000 + $0 }) {
    a1.append(v)
  }
  expectEqual(24, a1.count)
  expectGE(a1.capacity, 24)
  a1.append(1250)
  expectGT(a1.capacity, 24)
}

ArrayTestSuite.test("init(arrayLiteral:)") {
  do {
    let empty = Array<Int>()
    expectEqual(0, empty.count)
  }
  do {
    let a = Array(arrayLiteral: 1010)
    expectEqual(1, a.count)
    expectEqual(1010, a[0])
  }
  do {
    let a = Array(arrayLiteral: 1010, 1020)
    expectEqual(2, a.count)
    expectEqual(1010, a[0])
    expectEqual(1020, a[1])
  }
  do {
    let a = Array(arrayLiteral: 1010, 1020, 1030)
    expectEqual(3, a.count)
    expectEqual(1010, a[0])
    expectEqual(1020, a[1])
    expectEqual(1030, a[2])
  }
  do {
    let a = Array(arrayLiteral: 1010, 1020, 1030, 1040)
    expectEqual(4, a.count)
    expectEqual(1010, a[0])
    expectEqual(1020, a[1])
    expectEqual(1030, a[2])
    expectEqual(1040, a[3])
  }
  do {
    let a: Array<Int> = [ 1010, 1020, 1030 ]
    expectEqual(3, a.count)
    expectEqual(1010, a[0])
    expectEqual(1020, a[1])
    expectEqual(1030, a[2])
  }
}

ArrayTestSuite.test("init(repeating:count:)") {
  do {
    let a = Array(repeating: 1010, count: 5)
    expectEqual(a.count, 5)
    expectEqual(1010, a[0])
    expectEqual(1010, a[1])
    expectEqual(1010, a[2])
    expectEqual(1010, a[3])
    expectEqual(1010, a[4])
  }
}

#if _runtime(_ObjC)
//===----------------------------------------------------------------------===//
// NSArray -> Array bridging tests.
//===----------------------------------------------------------------------===//

ArrayTestSuite.test("BridgedFromObjC.Verbatim.ArrayIsCopied") {
  var (a, nsa) = getBridgedVerbatimArrayAndNSMutableArray()
  expectTrue(isCocoaArray(a))

  // Find an existing value.
  do {
    let v = a[0] as! TestObjCValueTy
    expectEqual(1010, v.value)
  }

  // Remove the value from the NSMutableArray.
  nsa.removeObject(at: 0)

  // Find an existing value, again.
  do {
    let v = a[0] as! TestObjCValueTy
    expectEqual(1010, v.value)
  }
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.ArrayIsCopied") {
  var (a, nsa) = getBridgedNonverbatimArrayAndNSMutableArray()
  expectTrue(isNativeArray(a))

  // Find an existing value.
  do {
    let v = a[0]
    expectEqual(1010, v.value)
  }

  // Remove the value from the NSMutableArray.
  nsa.removeObject(at: 0)

  // Find an existing value, again.
  do {
    let v = a[0]
    expectEqual(1010, v.value)
  }
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.NSArrayIsRetained") {
  let nsa: NSArray = autoreleasepool {
    NSArray(array: getAsNSArray([1010, 1020, 1030]))
  }
  
  let a: [AnyObject] = convertNSArrayToArray(nsa)
  
  let bridgedBack: NSArray = convertArrayToNSArray(a)
  
  expectEqual(
    unsafeBitCast(nsa, to: Int.self),
    unsafeBitCast(bridgedBack, to: Int.self))
  
  _blackHole(nsa)
  _blackHole(a)
  _blackHole(bridgedBack)
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.NSArrayIsCopied") {
  let nsa: NSArray = autoreleasepool {
    NSArray(array: getAsNSArray([1010, 1020, 1030]))
  }
  
  let a: [TestBridgedValueTy] = convertNSArrayToArray(nsa)
  
  let bridgedBack: NSArray = convertArrayToNSArray(a)
  
  expectNotEqual(
    unsafeBitCast(nsa, to: Int.self),
    unsafeBitCast(bridgedBack, to: Int.self))
  
  _blackHole(nsa)
  _blackHole(a)
  _blackHole(bridgedBack)
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.ImmutableArrayIsRetained") {
  let nsa: NSArray = CustomImmutableNSArray(_privateInit: ())
  
  CustomImmutableNSArray.timesCopyWithZoneWasCalled = 0
  CustomImmutableNSArray.timesObjectAtIndexWasCalled = 0
  CustomImmutableNSArray.timesObjectEnumeratorWasCalled = 0
  CustomImmutableNSArray.timesCountWasCalled = 0
  let a: [AnyObject] = convertNSArrayToArray(nsa)
  expectEqual(1, CustomImmutableNSArray.timesCopyWithZoneWasCalled)
  expectEqual(0, CustomImmutableNSArray.timesObjectAtIndexWasCalled)
  expectEqual(0, CustomImmutableNSArray.timesObjectEnumeratorWasCalled)
  expectEqual(0, CustomImmutableNSArray.timesCountWasCalled)
  
  let bridgedBack: NSArray = convertArrayToNSArray(a)
  expectEqual(
    unsafeBitCast(nsa, to: Int.self),
    unsafeBitCast(bridgedBack, to: Int.self))
  
  _blackHole(nsa)
  _blackHole(a)
  _blackHole(bridgedBack)
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.ImmutableArrayIsCopied") {
  let nsa: NSArray = CustomImmutableNSArray(_privateInit: ())

  CustomImmutableNSArray.timesCopyWithZoneWasCalled = 0
  CustomImmutableNSArray.timesObjectAtIndexWasCalled = 0
  CustomImmutableNSArray.timesObjectEnumeratorWasCalled = 0
  CustomImmutableNSArray.timesCountWasCalled = 0
  TestBridgedValueTy.bridgeOperations = 0
  let a: [TestBridgedValueTy] = convertNSArrayToArray(nsa)
  //FIXME: Why is this copied?
  expectEqual(1, CustomImmutableNSArray.timesCopyWithZoneWasCalled)
  expectEqual(3, CustomImmutableNSArray.timesObjectAtIndexWasCalled)
  expectNotEqual(0, CustomImmutableNSArray.timesCountWasCalled)
  expectEqual(3, TestBridgedValueTy.bridgeOperations)

  let bridgedBack: NSArray = convertArrayToNSArray(a)
  expectNotEqual(
    unsafeBitCast(nsa, to: Int.self),
    unsafeBitCast(bridgedBack, to: Int.self))

  _blackHole(nsa)
  _blackHole(a)
  _blackHole(bridgedBack)
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.Subscript") {
  let a = getBridgedVerbatimArray()
  let identity1 = a._rawIdentifier()
  expectTrue(isCocoaArray(a))

  // Find an existing value.
  do {
    var v = a[0]
    expectEqual(1010, (v as! TestObjCValueTy).value)

    v = a[1]
    expectEqual(1020, (v as! TestObjCValueTy).value)

    v = a[2]
    expectEqual(1030, (v as! TestObjCValueTy).value)
  }
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.Subscript") {
  var a = getBridgedNonverbatimArray()
  let identity1 = a._rawIdentifier()
  expectTrue(isNativeArray(a))

  // Find an existing value.
  do {
    var v = a[0]
    expectEqual(1010, v.value)

    v = a[1]
    expectEqual(1020, v.value)

    v = a[2]
    expectEqual(1030, v.value)
  }
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.RemoveAt") {
  var a = getBridgedVerbatimArray()
  let identity = a._rawIdentifier()
  expectTrue(isCocoaArray(a))

  let index = 0
  expectEqual(1010, (a[index] as! TestObjCValueTy).value)
  expectEqual(identity, a._rawIdentifier())

  let removedElement = a.remove(at: index)
  expectNotEqual(identity, a._rawIdentifier())
  expectTrue(isNativeArray(a))
  expectEqual(1010, (removedElement as! TestObjCValueTy).value)
  expectEqual(2, a.count)
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.RemoveAt") {
  var a = getBridgedNonverbatimArray()
  let identity = a._rawIdentifier()
  expectTrue(isNativeArray(a))

  let index = 0
  expectEqual(1010, a[index].value)
  expectEqual(identity, a._rawIdentifier())

  let removedElement = a.remove(at: index)
  expectEqual(identity, a._rawIdentifier())
  expectTrue(isNativeArray(a))
  expectEqual(1010, removedElement.value)
  expectEqual(2, a.count)
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.RemoveAll") {
  do {
    var a = getBridgedVerbatimArray()
    let identity1 = a._rawIdentifier()
    expectTrue(isCocoaArray(a))
    let originalCapacity = a.count
    expectEqual(3, a.count)
    expectEqual(1010, (a[0] as! TestObjCValueTy).value)

    a.removeAll()
    expectNotEqual(identity1, a._rawIdentifier())
    expectLT(a._buffer.capacity, originalCapacity)
    expectEqual(0, a.count)
  }

  do {
    var a = getBridgedVerbatimArray()
    let identity1 = a._rawIdentifier()
    expectTrue(isCocoaArray(a))
    let originalCapacity = a.count
    expectEqual(3, a.count)
    expectEqual(1010, (a[0] as! TestObjCValueTy).value)

    a.removeAll(keepingCapacity: true)
    expectNotEqual(identity1, a._rawIdentifier())
    expectGE(a._buffer.capacity, originalCapacity)
    expectEqual(0, a.count)
  }

  do {
    var a1 = getBridgedVerbatimArray()
    let identity1 = a1._rawIdentifier()
    expectTrue(isCocoaArray(a1))
    let originalCapacity = a1.count
    expectEqual(3, a1.count)
    expectEqual(1010, (a1[0] as! TestObjCValueTy).value)

    var a2 = a1
    a2.removeAll()
    let identity2 = a2._rawIdentifier()
    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity2, identity1)
    expectEqual(3, a1.count)
    expectEqual(1010, (a1[0] as! TestObjCValueTy).value)
    expectLT(a2._buffer.capacity, originalCapacity)
    expectEqual(0, a2.count)
  }

  do {
    var a1 = getBridgedVerbatimArray()
    let identity1 = a1._rawIdentifier()
    expectTrue(isCocoaArray(a1))
    let originalCapacity = a1.count
    expectEqual(3, a1.count)
    expectEqual(1010, (a1[0] as! TestObjCValueTy).value)

    var a2 = a1
    a2.removeAll(keepingCapacity: true)
    let identity2 = a2._rawIdentifier()
    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity2, identity1)
    expectEqual(3, a1.count)
    expectEqual(1010, (a1[0] as! TestObjCValueTy).value)
    expectGE(a2._buffer.capacity, originalCapacity)
    expectEqual(0, a2.count)
  }
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.RemoveAll") {
  do {
    var a = getBridgedNonverbatimArray()
    let identity1 = a._rawIdentifier()
    expectTrue(isNativeArray(a))
    let originalCapacity = a.count
    expectEqual(3, a.count)
    expectEqual(1010, a[0].value)

    a.removeAll()
    expectNotEqual(identity1, a._rawIdentifier())
    expectLT(a._buffer.capacity, originalCapacity)
    expectEqual(0, a.count)
  }

  do {
    var a = getBridgedNonverbatimArray()
    let identity1 = a._rawIdentifier()
    expectTrue(isNativeArray(a))
    let originalCapacity = a.count
    expectEqual(3, a.count)
    expectEqual(1010, a[0].value)

    a.removeAll(keepingCapacity: true)
    expectEqual(identity1, a._rawIdentifier())
    expectGE(a._buffer.capacity, originalCapacity)
    expectEqual(0, a.count)
  }

  do {
    var a1 = getBridgedNonverbatimArray()
    let identity1 = a1._rawIdentifier()
    expectTrue(isNativeArray(a1))
    let originalCapacity = a1.count
    expectEqual(3, a1.count)
    expectEqual(1010, a1[0].value)

    var a2 = a1
    a2.removeAll()
    let identity2 = a2._rawIdentifier()
    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity2, identity1)
    expectEqual(3, a1.count)
    expectEqual(1010, a1[0].value)
    expectLT(a2._buffer.capacity, originalCapacity)
    expectEqual(0, a2.count)
  }

  do {
    var a1 = getBridgedNonverbatimArray()
    let identity1 = a1._rawIdentifier()
    expectTrue(isNativeArray(a1))
    let originalCapacity = a1.count
    expectEqual(3, a1.count)
    expectEqual(1010, a1[0].value)

    var a2 = a1
    a2.removeAll(keepingCapacity: true)
    let identity2 = a2._rawIdentifier()
    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity2, identity1)
    expectEqual(3, a1.count)
    expectEqual(1010, a1[0].value)
    expectGE(a2._buffer.capacity, originalCapacity)
    expectEqual(0, a2.count)
  }
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.Count") {
  let a = getBridgedVerbatimArray()
  let identity1 = a._rawIdentifier()
  expectTrue(isCocoaArray(a))

  expectEqual(3, a.count)
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.Count") {
  let a = getBridgedNonverbatimArray()
  let identity1 = a._rawIdentifier()
  expectTrue(isNativeArray(a))

  expectEqual(3, a.count)
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.Generate") {
  let a = getBridgedVerbatimArray()
  let identity1 = a._rawIdentifier()
  expectTrue(isCocoaArray(a))

  var iter = a.makeIterator()
  var values = Array<Int>()
  while let value = iter.next() {
    values.append((value as! TestObjCValueTy).value)
  }
  expectEqual(values, [1010, 1020, 1030])
  expectNil(iter.next())
  expectNil(iter.next())
  expectNil(iter.next())
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.Generate") {
  let a = getBridgedNonverbatimArray()
  let identity1 = a._rawIdentifier()
  expectTrue(isNativeArray(a))

  var iter = a.makeIterator()
  var values = Array<Int>()
  while let value = iter.next() {
    values.append(value.value)
  }
  expectEqual(values, [1010, 1020, 1030])
  expectNil(iter.next())
  expectNil(iter.next())
  expectNil(iter.next())
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.Generate_Empty") {
  let a = getBridgedVerbatimArray([])
  let identity1 = a._rawIdentifier()
  expectTrue(isCocoaArray(a))

  var iter = a.makeIterator()
  expectNil(iter.next())
  expectNil(iter.next())
  expectNil(iter.next())
  expectNil(iter.next())
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.Generate_Empty") {
  let a = getBridgedNonverbatimArray([])
  let identity1 = a._rawIdentifier()
  expectTrue(isNativeArray(a))

  var iter = a.makeIterator()
  expectNil(iter.next())
  expectNil(iter.next())
  expectNil(iter.next())
  expectNil(iter.next())
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.Generate_Huge") {
  let a = getHugeBridgedVerbatimArray()
  let identity1 = a._rawIdentifier()
  expectTrue(isCocoaArray(a))

  var iter = a.makeIterator()
  var values = Array<Int>()
  while let value = iter.next() {
    values.append((value as! TestObjCValueTy).value)
  }
  var expectedValues = Array<Int>()
  for i in 1...32 {
    expectedValues += [1000 + i]
  }
  expectEqual(values, expectedValues)
  expectNil(iter.next())
  expectNil(iter.next())
  expectNil(iter.next())
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.Generate_Huge") {
  let a = getHugeBridgedNonverbatimArray()
  let identity1 = a._rawIdentifier()
  expectTrue(isNativeArray(a))

  var iter = a.makeIterator()
  var values = Array<Int>()
  while let value = iter.next() {
    values.append(value.value)
  }
  var expectedValues = Array<Int>()
  for i in 1...32 {
    expectedValues += [1000 + i]
  }
  expectEqual(values, expectedValues)
  expectNil(iter.next())
  expectNil(iter.next())
  expectNil(iter.next())
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.EqualityTest_Empty") {
  let a1 = getBridgedVerbatimEquatableArray([])
  let identity1 = a1._rawIdentifier()
  expectTrue(isCocoaArray(a1))

  let a2 = getBridgedVerbatimEquatableArray([])
  let identity2 = a2._rawIdentifier()
  expectTrue(isCocoaArray(a2))

  // We can't check that `identity1 != identity2` because Foundation might be
  // returning the same singleton NSArray for empty arrays.

  expectEqual(a1, a2)
  expectEqual(identity1, a1._rawIdentifier())
  expectEqual(identity2, a2._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Nonverbatim.EqualityTest_Empty") {
  var a1 = getBridgedNonverbatimEquatableArray([])
  a1.append(TestBridgedEquatableValueTy(1))
  a1.removeLast()
  let identity1 = a1._rawIdentifier()
  expectTrue(isNativeArray(a1))

  let a2 = getBridgedNonverbatimEquatableArray([])
  let identity2 = a2._rawIdentifier()
  expectTrue(isNativeArray(a2))
  expectNotEqual(identity1, identity2)

  expectEqual(a1, a2)
  expectEqual(identity1, a1._rawIdentifier())
  expectEqual(identity2, a2._rawIdentifier())
}

ArrayTestSuite.test("BridgedFromObjC.Verbatim.EqualityTest_Small") {
  func helper(_ na1: Array<Int>, _ na2: Array<Int>, _ expectedEq: Bool) {
    let a1 = getBridgedVerbatimEquatableArray(na1)
    let identity1 = a1._rawIdentifier()
    expectTrue(isCocoaArray(a1))

    var a2 = getBridgedVerbatimEquatableArray(na2)
    var identity2 = a2._rawIdentifier()
    expectTrue(isCocoaArray(a2))

    do {
      let eq1 = (a1 == a2)
      expectEqual(eq1, expectedEq)

      let eq2 = (a2 == a1)
      expectEqual(eq2, expectedEq)

      let neq1 = (a1 != a2)
      expectNotEqual(neq1, expectedEq)

      let neq2 = (a2 != a1)
      expectNotEqual(neq2, expectedEq)
    }
    expectEqual(identity1, a1._rawIdentifier())
    expectEqual(identity2, a2._rawIdentifier())

    a2.append(TestObjCEquatableValueTy(1111))
    a2.removeLast()
    expectTrue(isNativeArray(a2))
    expectNotEqual(identity2, a2._rawIdentifier())
    identity2 = a2._rawIdentifier()

    do {
      let eq1 = (a1 == a2)
      expectEqual(eq1, expectedEq)

      let eq2 = (a2 == a1)
      expectEqual(eq2, expectedEq)

      let neq1 = (a1 != a2)
      expectNotEqual(neq1, expectedEq)

      let neq2 = (a2 != a1)
      expectNotEqual(neq2, expectedEq)
    }
    expectEqual(identity1, a1._rawIdentifier())
    expectEqual(identity2, a2._rawIdentifier())
  }

  helper([], [], true)

  helper([1010],
         [1010],
         true)

  helper([1010, 1020],
         [1010, 1020],
         true)

  helper([1010, 1020, 1030],
         [1010, 1020, 1030],
         true)

  helper([1010, 1020, 1030],
         [1010, 1020, 1111],
         false)

  helper([1010, 1020, 1030],
         [1010, 1020],
         false)

  helper([1010, 1020, 1030],
         [1010],
         false)

  helper([1010, 1020, 1030],
         [],
         false)

  helper([1010, 1020, 1030],
         [1010, 1020, 1030, 1040],
         false)
}

//===---
// Array -> NSArray bridging tests.
//
// Values are bridged verbatim.
//===---

ArrayTestSuite.test("BridgedToObjC.Verbatim.Count") {
  let d = getBridgedNSArrayOfRefTypesBridgedVerbatim()

  expectEqual(3, d.count)
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.ObjectForKey") {
  let a = getBridgedNSArrayOfRefTypesBridgedVerbatim()

  var v: AnyObject? = a.object(at: 0) as AnyObject
  expectEqual(1010, (v as! TestObjCValueTy).value)
  let idValue10 = unsafeBitCast(v, to: UInt.self)

  v = a.object(at: 1) as AnyObject
  expectEqual(1020, (v as! TestObjCValueTy).value)
  let idValue20 = unsafeBitCast(v, to: UInt.self)

  v = a.object(at: 2) as AnyObject
  expectEqual(1030, (v as! TestObjCValueTy).value)
  let idValue30 = unsafeBitCast(v, to: UInt.self)

  for _ in 0..<3 {
    expectEqual(idValue10, unsafeBitCast(
      a.object(at: 0) as AnyObject, to: UInt.self))

    expectEqual(idValue20, unsafeBitCast(
      a.object(at: 1) as AnyObject, to: UInt.self))

    expectEqual(idValue30, unsafeBitCast(
      a.object(at: 2) as AnyObject, to: UInt.self))
  }

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.KeyEnumerator.NextObject") {
  let a = getBridgedNSArrayOfRefTypesBridgedVerbatim()

  var capturedIdentities = Array<UInt>()

  for _ in 0..<3 {
    let enumerator = a.objectEnumerator()

    var values = Array<Int>()
    var identities = Array<UInt>()
    while let value = enumerator.nextObject() {
      let valueObj = (value as! TestObjCValueTy)
      values.append(valueObj.value)

      let identity = unsafeBitCast(valueObj, to: UInt.self)
      identities.append(identity)
    }
    expectEqual([ 1010, 1020, 1030 ], values)

    if capturedIdentities.isEmpty {
      capturedIdentities = identities
    } else {
      expectEqual(capturedIdentities, identities)
    }

    expectNil(enumerator.nextObject())
    expectNil(enumerator.nextObject())
    expectNil(enumerator.nextObject())
  }

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.ObjectEnumerator.NextObject_Empty") {
  let a = getBridgedEmptyNSArray()
  let enumerator = a.objectEnumerator()

  expectNil(enumerator.nextObject())
  expectNil(enumerator.nextObject())
  expectNil(enumerator.nextObject())
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.ObjectEnumerator.FastEnumeration.UseFromSwift") {
  let a = getBridgedNSArrayOfRefTypesBridgedVerbatim()

  checkArrayFastEnumerationFromSwift(
    [ 1010, 1020, 1030 ],
    a, { a.objectEnumerator() },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.ObjectEnumerator.FastEnumeration.UseFromObjC") {
  let a = getBridgedNSArrayOfRefTypesBridgedVerbatim()

  checkArrayFastEnumerationFromObjC(
    [ 1010, 1020, 1030 ],
    a, { a.objectEnumerator() },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.ObjectEnumerator.FastEnumeration_Empty") {
  let a = getBridgedEmptyNSArray()

  checkArrayFastEnumerationFromSwift(
    [], a, { a.objectEnumerator() },
    { ($0 as! TestObjCValueTy).value })

  checkArrayFastEnumerationFromObjC(
    [], a, { a.objectEnumerator() },
    { ($0 as! TestObjCValueTy).value })
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.FastEnumeration.UseFromSwift") {
  let a = getBridgedNSArrayOfRefTypesBridgedVerbatim()

  checkArrayFastEnumerationFromSwift(
    [ 1010, 1020, 1030 ],
    a, { a },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.FastEnumeration.UseFromObjC") {
  let a = getBridgedNSArrayOfRefTypesBridgedVerbatim()

  checkArrayFastEnumerationFromObjC(
    [ 1010, 1020, 1030 ],
    a, { a },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Verbatim.FastEnumeration_Empty") {
  let a = getBridgedEmptyNSArray()

  checkArrayFastEnumerationFromSwift(
    [], a, { a },
    { ($0 as! TestObjCValueTy).value })

  checkArrayFastEnumerationFromObjC(
    [], a, { a },
    { ($0 as! TestObjCValueTy).value })
}

//===---
// Array -> NSArray bridging tests.
//
// Values are bridged non-verbatim.
//===---

ArrayTestSuite.test("BridgedToObjC.KeyValue_ValueTypesCustomBridged") {
  let a = getBridgedNSArrayOfObjValue_ValueTypesCustomBridged()
  let enumerator = a.objectEnumerator()

  var values = Array<Int>()
  while let valueObj = enumerator.nextObject() {
    let value: AnyObject = valueObj as AnyObject
    let v = (value as! TestObjCValueTy).value
    values.append(v)
  }
  expectEqual([ 1010, 1020, 1030 ], values)

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Custom.ObjectEnumerator.FastEnumeration.UseFromSwift") {
  let a = getBridgedNSArrayOfObjValue_ValueTypesCustomBridged()

  checkArrayFastEnumerationFromSwift(
    [ 1010, 1020, 1030 ],
    a, { a.objectEnumerator() },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Custom.ObjectEnumerator.FastEnumeration.UseFromSwift.Partial") {
  let a = getBridgedNSArrayOfObjValue_ValueTypesCustomBridged(
    numElements: 9)

  checkArrayEnumeratorPartialFastEnumerationFromSwift(
    [ 1010, 1020, 1030, 1040, 1050,
      1060, 1070, 1080, 1090 ],
    a, maxFastEnumerationItems: 5,
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 9)
}

ArrayTestSuite.test("BridgedToObjC.Custom.ObjectEnumerator.FastEnumeration.UseFromObjC") {
  let a = getBridgedNSArrayOfObjValue_ValueTypesCustomBridged()

  checkArrayFastEnumerationFromObjC(
    [ 1010, 1020, 1030 ],
    a, { a.objectEnumerator() },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Custom.FastEnumeration.UseFromSwift") {
  let a = getBridgedNSArrayOfObjValue_ValueTypesCustomBridged()

  checkArrayFastEnumerationFromSwift(
    [ 1010, 1020, 1030 ],
    a, { a },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Custom.FastEnumeration.UseFromObjC") {
  let a = getBridgedNSArrayOfObjValue_ValueTypesCustomBridged()

  checkArrayFastEnumerationFromObjC(
    [ 1010, 1020, 1030 ],
    a, { a },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Custom.FastEnumeration_Empty") {
  let a = getBridgedNSArrayOfObjValue_ValueTypesCustomBridged(
    numElements: 0)

  checkArrayFastEnumerationFromSwift(
    [], a, { a },
    { ($0 as! TestObjCValueTy).value })

  checkArrayFastEnumerationFromObjC(
    [], a, { a },
    { ($0 as! TestObjCValueTy).value })
}

ArrayTestSuite.test("BridgedToObjC.Key_ValueTypeCustomBridged") {
  let a = getBridgedNSArrayOfObj_ValueTypeCustomBridged()
  let enumerator = a.objectEnumerator()

  var values = Array<Int>()
  while let valueObj = enumerator.nextObject() {
    let value: AnyObject = valueObj as AnyObject
    let v = (value as! TestObjCValueTy).value
    values.append(v)
  }
  expectEqual([ 1010, 1020, 1030 ], values)

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("BridgedToObjC.Value_ValueTypeCustomBridged") {
  let a = getBridgedNSArrayOfValue_ValueTypeCustomBridged()
  let enumerator = a.objectEnumerator()

  var values = Array<Int>()
  while let valueObj = enumerator.nextObject() {
    let value: AnyObject = valueObj as AnyObject
    let v = (value as! TestObjCValueTy).value
    values.append(v)
  }
  expectEqual([ 1010, 1020, 1030 ], values)

  expectAutoreleasedValues(unopt: 3)
}

//===---
// NSArray -> Array -> NSArray bridging tests.
//===---

ArrayTestSuite.test("BridgingRoundtrip") {
  let a = getRoundtripBridgedNSArray()
  let enumerator = a.objectEnumerator()

  var values = Array<Int>()
  while let valueObj = enumerator.nextObject() {
    let value: AnyObject = valueObj as AnyObject
    let v = (value as! TestObjCValueTy).value
    values.append(v)
  }
  expectEqual([ 1010, 1020, 1030 ], values)
}

//===---
// NSArray -> Array implicit conversion.
//===---

ArrayTestSuite.test("NSArrayToArrayConversion") {
  let values = [ 1010, 1020, 1030 ].map { TestObjCValueTy($0) }

  let nsa = NSArray(array: values)

  let a: Array = nsa as Array

  var bridgedValues = Array<Int>()
  for value in a {
    let v = (value as! TestObjCValueTy).value
    bridgedValues.append(v)
  }
  expectEqual([ 1010, 1020, 1030 ], bridgedValues)
}

ArrayTestSuite.test("ArrayToNSArrayConversion") {
  var a = Array<TestObjCValueTy>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))
  let nsa: NSArray = a as NSArray

  checkArrayFastEnumerationFromSwift(
    [ 1010, 1020, 1030 ],
    nsa, { a as NSArray },
    { ($0 as! TestObjCValueTy).value })

  expectAutoreleasedValues(unopt: 3)
}

//===---
// Array upcasts
//===---

ArrayTestSuite.test("ArrayUpcastEntryPoint") {
  var a = Array<TestObjCValueTy>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  var aAsAnyObject: Array<AnyObject> = _arrayForceCast(a)

  expectEqual(3, aAsAnyObject.count)
  var v: AnyObject = aAsAnyObject[0]
  expectEqual(1010, (v as! TestObjCValueTy).value)

  v = aAsAnyObject[1]
  expectEqual(1020, (v as! TestObjCValueTy).value)

  v = aAsAnyObject[2]
  expectEqual(1030, (v as! TestObjCValueTy).value)
}

ArrayTestSuite.test("ArrayUpcast") {
  var a = Array<TestObjCValueTy>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  var dAsAnyObject: Array<AnyObject> = a

  expectEqual(3, dAsAnyObject.count)
  var v: AnyObject = dAsAnyObject[0]
  expectEqual(1010, (v as! TestObjCValueTy).value)

  v = dAsAnyObject[1]
  expectEqual(1020, (v as! TestObjCValueTy).value)

  v = dAsAnyObject[2]
  expectEqual(1030, (v as! TestObjCValueTy).value)
}

ArrayTestSuite.test("ArrayUpcastBridgedEntryPoint") {
  var a = Array<TestBridgedValueTy>()
  a.append(TestBridgedValueTy(1010))
  a.append(TestBridgedValueTy(1020))
  a.append(TestBridgedValueTy(1030))

  do {
    var aOO: Array<AnyObject> = _arrayConditionalCast(a)!

    expectEqual(3, aOO.count)
    var v: AnyObject = aOO[0]
    expectEqual(1010, (v as! TestBridgedValueTy).value)

    v = aOO[1]
    expectEqual(1020, (v as! TestBridgedValueTy).value)

    v = aOO[2]
    expectEqual(1030, (v as! TestBridgedValueTy).value)
  }
}

ArrayTestSuite.test("ArrayUpcastBridged") {
  var a = Array<TestBridgedValueTy>()
  a.append(TestBridgedValueTy(1010))
  a.append(TestBridgedValueTy(1020))
  a.append(TestBridgedValueTy(1030))

  do {
    var aOO = a as Array<AnyObject>

    expectEqual(3, aOO.count)
    var v: AnyObject = aOO[0]
    expectEqual(1010, (v as! TestBridgedValueTy).value)

    v = aOO[1]
    expectEqual(1020, (v as! TestBridgedValueTy).value)

    v = aOO[2]
    expectEqual(1030, (v as! TestBridgedValueTy).value)
  }
}

//===---
// Array downcasts
//===---

ArrayTestSuite.test("ArrayDowncastEntryPoint") {
  var a = Array<AnyObject>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  // Successful downcast.
  let aCC: Array<TestObjCValueTy> = _arrayForceCast(a)
  expectEqual(3, aCC.count)
  var v = aCC[0]
  expectEqual(1010, v.value)

  v = aCC[1]
  expectEqual(1020, v.value)

  v = aCC[2]
  expectEqual(1030, v.value)

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("ArrayDowncast") {
  var a = Array<AnyObject>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  // Successful downcast.
  let aCC = a as! Array<TestObjCValueTy>
  expectEqual(3, aCC.count)
  var v = aCC[0]
  expectEqual(1010, v.value)

  v = aCC[1]
  expectEqual(1020, v.value)

  v = aCC[2]
  expectEqual(1030, v.value)

  expectAutoreleasedValues(unopt: 3)
}

ArrayTestSuite.test("ArrayDowncastConditionalEntryPoint") {
  var a = Array<AnyObject>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  // Successful downcast.
  if let aCC
       = _arrayConditionalCast(a) as Array<TestObjCValueTy>? {
    expectEqual(3, aCC.count)
    var v = aCC[0]
    expectEqual(1010, v.value)

    v = aCC[1]
    expectEqual(1020, v.value)

    v = aCC[2]
    expectEqual(1030, v.value)
  } else {
    expectTrue(false)
  }

  // Unsuccessful downcast
  a[0] = 17 as NSNumber
  a[1] = "hello" as NSString
  if let _ = _arrayConditionalCast(a) as Array<TestObjCValueTy>? {
    expectTrue(false)
  }
}

ArrayTestSuite.test("ArrayDowncastConditional") {
  var a = Array<AnyObject>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  // Successful downcast.
  if let aCC = a as? Array<TestObjCValueTy> {
    expectEqual(3, aCC.count)
    var v = aCC[0]
    expectEqual(1010, v.value)

    v = aCC[1]
    expectEqual(1020, v.value)

    v = aCC[2]
    expectEqual(1030, v.value)
  } else {
    expectTrue(false)
  }

  // Unsuccessful downcast
  a[0] = 17 as NSNumber
  a[1] = "hello" as NSString
  if let _ = a as? Array<TestObjCValueTy> {
    expectTrue(false)
  }
}

ArrayTestSuite.test("ArrayBridgeFromObjectiveCEntryPoint") {
  var a = Array<AnyObject>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  // Successful downcast.
  let aCV: Array<TestBridgedValueTy> = _arrayConditionalCast(a)!
  do {
    expectEqual(3, aCV.count)
    var v = aCV[0]
    expectEqual(1010, v.value)

    v = aCV[1]
    expectEqual(1020, v.value)

    v = aCV[2]
    expectEqual(1030, v.value)
  }

  // // Successful downcast.
  let aVC: Array<TestObjCValueTy> = _arrayConditionalCast(a)!
  do {
    expectEqual(3, aVC.count)
    var v = aVC[0]
    expectEqual(1010, v.value)

    v = aVC[1]
    expectEqual(1020, v.value)

    v = aVC[2]
    expectEqual(1030, v.value)
  }
}

ArrayTestSuite.test("ArrayBridgeFromObjectiveC") {
  var a = Array<AnyObject>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  // Successful downcast.
  let aCV = a as! Array<TestBridgedValueTy>
  do {
    expectEqual(3, aCV.count)
    var v = aCV[0]
    expectEqual(1010, v.value)

    v = aCV[1]
    expectEqual(1020, v.value)

    v = aCV[2]
    expectEqual(1030, v.value)
  }

  // Successful downcast.
  let aVC = a as! Array<TestObjCValueTy>
  do {
    expectEqual(3, aVC.count)
    var v = aVC[0]
    expectEqual(1010, v.value)

    v = aVC[1]
    expectEqual(1020, v.value)

    v = aVC[2]
    expectEqual(1030, v.value)
  }
}

ArrayTestSuite.test("ArrayBridgeFromObjectiveCConditionalEntryPoint") {
  var a = Array<AnyObject>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  // Successful downcast.
  if let aCV = _arrayConditionalCast(a) as Array<TestBridgedValueTy>? {
    expectEqual(3, aCV.count)
    var v = aCV[0]
    expectEqual(1010, v.value)

    v = aCV[1]
    expectEqual(1020, v.value)

    v = aCV[2]
    expectEqual(1030, v.value)
  } else {
    expectTrue(false)
  }

  // Successful downcast.
  if let aVC = _arrayConditionalCast(a) as Array<TestObjCValueTy>? {
    expectEqual(3, aVC.count)
    var v = aVC[0]
    expectEqual(1010, v.value)

    v = aVC[1]
    expectEqual(1020, v.value)

    v = aVC[2]
    expectEqual(1030, v.value)
  } else {
    expectTrue(false)
  }

  // Unsuccessful downcasts
  a[0] = 17 as NSNumber
  a[1] = "hello" as NSString
  if let _ = _arrayConditionalCast(a) as Array<TestBridgedValueTy>? {
    expectTrue(false)
  }
  if let _ = _arrayConditionalCast(a) as Array<TestObjCValueTy>? {
    expectTrue(false)
  }
}

ArrayTestSuite.test("ArrayBridgeFromObjectiveCConditional") {
  var a = Array<AnyObject>()
  a.append(TestObjCValueTy(1010))
  a.append(TestObjCValueTy(1020))
  a.append(TestObjCValueTy(1030))

  // Successful downcast.
  if let aCV = a as? Array<TestBridgedValueTy> {
    expectEqual(3, aCV.count)
    var v = aCV[0]
    expectEqual(1010, v.value)

    v = aCV[1]
    expectEqual(1020, v.value)

    v = aCV[2]
    expectEqual(1030, v.value)
  } else {
    expectTrue(false)
  }

  // Successful downcast.
  if let aVC = a as? Array<TestObjCValueTy> {
    expectEqual(3, aVC.count)
    var v = aVC[0]
    expectEqual(1010, v.value)

    v = aVC[1]
    expectEqual(1020, v.value)

    v = aVC[2]
    expectEqual(1030, v.value)
  } else {
    expectTrue(false)
  }

  // Unsuccessful downcasts
  a[0] = 17 as NSNumber
  a[1] = "hello" as NSString
  if let _ = a as? Array<TestBridgedValueTy> {
    expectTrue(false)
  }
  if let _ = a as? Array<TestObjCValueTy> {
    expectTrue(false)
  }
}

#endif

//===---
// Check that iterators traverse a snapshot of the collection.
//===---

ArrayTestSuite.test("mutationDoesNotAffectIterator/subscript/store") {
  var array = getDerivedAPIsArray()
  let iter = array.makeIterator()
  array[0] = 1011

  expectEqual([1010 ,1020, 1030], Array(IteratorSequence(iter)))
}

ArrayTestSuite.test("mutationDoesNotAffectIterator/removeAt,1") {
  var array = getDerivedAPIsArray()
  let iter = array.makeIterator()
  expectEqual(1010, array.remove(at: 0))

  expectEqual([1010 ,1020, 1030], Array(IteratorSequence(iter)))
}

ArrayTestSuite.test("mutationDoesNotAffectIterator/removeAt,all") {
  var array = getDerivedAPIsArray()
  let iter = array.makeIterator()
  expectEqual(1010, array.remove(at: 0))
  expectEqual(1020, array.remove(at: 0))
  expectEqual(1030, array.remove(at: 0))

  expectEqual([1010 ,1020, 1030], Array(IteratorSequence(iter)))
}

ArrayTestSuite.test(
  "mutationDoesNotAffectIterator/removeAll,keepingCapacity=false") {
  var array = getDerivedAPIsArray()
  let iter = array.makeIterator()
  array.removeAll(keepingCapacity: false)

  expectEqual([1010 ,1020, 1030], Array(IteratorSequence(iter)))
}

ArrayTestSuite.test(
  "mutationDoesNotAffectIterator/removeAll,keepingCapacity=true") {
  var array = getDerivedAPIsArray()
  let iter = array.makeIterator()
  array.removeAll(keepingCapacity: true)

  expectEqual([1010 ,1020, 1030], Array(IteratorSequence(iter)))
}

//===----------------------------------------------------------------------===//
// Native array tests
// FIXME: incomplete.
//===----------------------------------------------------------------------===//

ArrayTestSuite.test("Native/count/empty") {
  let a = [LifetimeTracked]()
  expectEqual(0, a.count)
}

ArrayTestSuite.test("Native/count") {
  let a = [ LifetimeTracked(10), LifetimeTracked(20), LifetimeTracked(30) ]
  expectEqual(3, a.count)
}

ArrayTestSuite.test("Native/isEmpty/empty") {
  let a = [LifetimeTracked]()
  expectTrue(a.isEmpty)
}

ArrayTestSuite.test("Native/isEmpty") {
  let a = [ LifetimeTracked(10), LifetimeTracked(20), LifetimeTracked(30) ]
  expectFalse(a.isEmpty)
}

% for Kind in ['Array', 'ContiguousArray']:
ArrayTestSuite.test("${Kind}/popLast") {
  // Empty
  do {
    var a = ${Kind}<Int>()
    let popped = a.popLast()
    expectNil(popped)
    expectTrue(a.isEmpty)
  }

  do {
    var popped = [Int]()
    var a: ${Kind}<Int> = [1010, 2020, 3030]
    while let element = a.popLast() {
      popped.append(element)
    }
    expectEqualSequence([1010, 2020, 3030], popped.reversed())
    expectTrue(a.isEmpty)
  }
}
% end

//===----------------------------------------------------------------------===//
// COW(🐄) tests
//===----------------------------------------------------------------------===//

class COWBox<
  T: Equatable & CustomStringConvertible>
  : Equatable, CustomStringConvertible {
  var value: T
  
  init(_ value: T) {
    self.value = value
  }
  
  var description: String {
    return "Boxed: \(value.description)"
  }
  
  static func ==(lhs: COWBox, rhs: COWBox) -> Bool {
    return lhs.value == rhs.value
  }
}

ArrayTestSuite.test("COW.Smoke") {
  var a1 = Array<COWBox<Int>>(repeating: COWBox(0), count: 10)
  let identity1 = a1._rawIdentifier()
  
  a1[0] = COWBox(1)
  a1[1] = COWBox(2)
  a1[2] = COWBox(3)
  
  var a2 = a1
  expectEqual(identity1, a2._rawIdentifier())
  
  a2[3] = COWBox(4)
  expectNotEqual(identity1, a2._rawIdentifier())
  
  a1[4] = COWBox(5)
  expectEqual(identity1, a1._rawIdentifier())
  
  _blackHole(a1)
  _blackHole(a2)  
}

ArrayTestSuite.test("COW.Fast.SubscriptWithIndexDoesNotReallocate") {
  var a = getCOWFastArray()
  let identity1 = a._rawIdentifier()
  let startIndex = a.startIndex

  expectNotEqual(0, a[startIndex])
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("COW.Slow.SubscriptWithIndexDoesNotReallocate") {
  var a = getCOWSlowArray()
  let identity1 = a._rawIdentifier()
  let startIndex = a.startIndex

  expectNotEqual(0, a[startIndex].value)
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("COW.Fast.RemoveAtDoesNotReallocate") {
  do {
    var a = getCOWFastArray()
    let identity1 = a._rawIdentifier()

    let index1 = 1
    expectEqual(identity1, a._rawIdentifier())

    expectEqual(2, a[index1])

    let removed = a.remove(at: index1)
    expectEqual(2, removed)

    expectEqual(identity1, a._rawIdentifier())
  }

  do {
    let a1 = getCOWFastArray()
    let identity1 = a1._rawIdentifier()

    var a2 = a1
    expectEqual(identity1, a1._rawIdentifier())
    expectEqual(identity1, a2._rawIdentifier())

    let index1 = 1
    expectEqual(2, a2[index1])
    expectEqual(identity1, a1._rawIdentifier())
    expectEqual(identity1, a2._rawIdentifier())

    let removed = a2.remove(at: index1)
    expectEqual(2, removed)

    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity1, a2._rawIdentifier())
  }
}

ArrayTestSuite.test("COW.Slow.RemoveAtDoesNotReallocate") {
  do {
    var a = getCOWSlowArray()
    let identity1 = a._rawIdentifier()

    let index1 = 1
    expectEqual(identity1, a._rawIdentifier())

    expectEqual(2, a[index1].value)

    let removed = a.remove(at: index1)
    expectEqual(2, removed.value)

    expectEqual(identity1, a._rawIdentifier())
  }

  do {
    let a1 = getCOWSlowArray()
    let identity1 = a1._rawIdentifier()

    var a2 = a1
    expectEqual(identity1, a1._rawIdentifier())
    expectEqual(identity1, a2._rawIdentifier())

    let index1 = 1
    expectEqual(2, a2[index1].value)
    expectEqual(identity1, a1._rawIdentifier())
    expectEqual(identity1, a2._rawIdentifier())

    let removed = a2.remove(at: index1)
    expectEqual(2, removed.value)

    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity1, a2._rawIdentifier())
  }
}

ArrayTestSuite.test("COW.Fast.RemoveAllDoesNotReallocate")
  .skip(.linuxAny(reason: "rdar://problem/34268868")).code {
  do {
    var a = getCOWFastArray()
    let originalCapacity = a.capacity
    expectEqual(3, a.count)
    expectEqual(2, a[1])

    a.removeAll()
    let identity1 = a._rawIdentifier()
    expectLT(a.capacity, originalCapacity)
    expectEqual(0, a.count)
    expectEqual(identity1, a._rawIdentifier())
  }

  do {
    var a = getCOWFastArray()
    let identity1 = a._rawIdentifier()
    let originalCapacity = a.capacity
    expectEqual(3, a.count)
    expectEqual(2, a[1])

    a.removeAll(keepingCapacity: true)
    expectEqual(identity1, a._rawIdentifier())
    expectEqual(originalCapacity, a.capacity)
    expectEqual(0, a.count)
  }

  do {
    var a1 = getCOWFastArray()
    let identity1 = a1._rawIdentifier()
    expectEqual(3, a1.count)
    expectEqual(2, a1[1])

    var a2 = a1
    a2.removeAll()
    let identity2 = a2._rawIdentifier()
    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity2, identity1)
    expectEqual(3, a1.count)
    expectEqual(2, a1[1])
    expectEqual(0, a2.count)

    // Keep variables alive.
    _blackHole(a1)
    _blackHole(a2)
  }

  do {
    var a1 = getCOWFastArray()
    let identity1 = a1._rawIdentifier()
    let originalCapacity = a1.capacity
    expectEqual(3, a1.count)
    expectEqual(2, a1[1])

    var a2 = a1
    a2.removeAll(keepingCapacity: true)
    let identity2 = a2._rawIdentifier()
    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity2, identity1)
    expectEqual(3, a1.count)
    expectEqual(2, a1[1])
    expectEqual(originalCapacity, a2.capacity)
    expectEqual(0, a2.count)

    // Keep variables alive.
    _blackHole(a1)
    _blackHole(a2)
  }
}

ArrayTestSuite.test("COW.Slow.RemoveAllDoesNotReallocate")
  .skip(.linuxAny(reason: "rdar://problem/34268868")).code {
  do {
    var a = getCOWSlowArray()
    let originalCapacity = a.capacity
    expectEqual(3, a.count)
    expectEqual(2, a[1].value)

    a.removeAll()
    let identity1 = a._rawIdentifier()
    expectLT(a.capacity, originalCapacity)
    expectEqual(0, a.count)
    expectEqual(identity1, a._rawIdentifier())
  }

  do {
    var a = getCOWSlowArray()
    let identity1 = a._rawIdentifier()
    let originalCapacity = a.capacity
    expectEqual(3, a.count)
    expectEqual(2, a[1].value)

    a.removeAll(keepingCapacity: true)
    expectEqual(identity1, a._rawIdentifier())
    expectEqual(originalCapacity, a.capacity)
    expectEqual(0, a.count)
  }

  do {
    var a1 = getCOWSlowArray()
    let identity1 = a1._rawIdentifier()
    expectEqual(3, a1.count)
    expectEqual(2, a1[1].value)

    var a2 = a1
    a2.removeAll()
    let identity2 = a2._rawIdentifier()
    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity2, identity1)
    expectEqual(3, a1.count)
    expectEqual(2, a1[1].value)
    expectEqual(0, a2.count)

    // Keep variables alive.
    _blackHole(a1)
    _blackHole(a2)
  }

  do {
    var a1 = getCOWSlowArray()
    let identity1 = a1._rawIdentifier()
    let originalCapacity = a1.capacity
    expectEqual(3, a1.count)
    expectEqual(2, a1[1].value)

    var a2 = a1
    a2.removeAll(keepingCapacity: true)
    let identity2 = a2._rawIdentifier()
    expectEqual(identity1, a1._rawIdentifier())
    expectNotEqual(identity2, identity1)
    expectEqual(3, a1.count)
    expectEqual(2, a1[1].value)
    expectEqual(originalCapacity, a2.capacity)
    expectEqual(0, a2.count)

    // Keep variables alive.
    _blackHole(a1)
    _blackHole(a2)
  }
}

ArrayTestSuite.test("COW.Fast.CountDoesNotReallocate") {
  let a = getCOWFastArray()
  let identity1 = a._rawIdentifier()

  expectEqual(3, a.count)
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("COW.Slow.CountDoesNotReallocate") {
  let a = getCOWSlowArray()
  let identity1 = a._rawIdentifier()

  expectEqual(3, a.count)
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("COW.Fast.GenerateDoesNotReallocate") {
  let a = getCOWFastArray()
  let identity1 = a._rawIdentifier()

  var iter = a.makeIterator()
  var copy = Array<Int>()
  while let value = iter.next() {
    copy.append(value)
  }
  expectEqual(copy, [ 1, 2, 3 ])
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("COW.Slow.GenerateDoesNotReallocate") {
  let a = getCOWSlowArray()
  let identity1 = a._rawIdentifier()

  var iter = a.makeIterator()
  var copy = Array<Int>()
  while let value = iter.next() {
    copy.append(value.value)
  }
  expectEqual(copy, [ 1, 2, 3 ])
  expectEqual(identity1, a._rawIdentifier())
}

ArrayTestSuite.test("COW.Fast.EqualityTestDoesNotReallocate") {
  let a1 = getCOWFastArray()
  let identity1 = a1._rawIdentifier()

  var a2 = getCOWFastArray()
  let identity2 = a2._rawIdentifier()

  expectEqual(a1, a2)
  expectEqual(identity1, a1._rawIdentifier())
  expectEqual(identity2, a2._rawIdentifier())

  a2[1] = 5
  expectTrue(a1 != a2)
  expectEqual(identity1, a1._rawIdentifier())
  expectEqual(identity2, a2._rawIdentifier())
}

ArrayTestSuite.test("COW.Slow.EqualityTestDoesNotReallocate") {
  let a1 = getCOWSlowArray()
  let identity1 = a1._rawIdentifier()

  var a2 = getCOWSlowArray()
  let identity2 = a2._rawIdentifier()

  expectEqual(a1, a2)
  expectEqual(identity1, a1._rawIdentifier())
  expectEqual(identity2, a2._rawIdentifier())

  a2[2] = COWBox(5)
  expectTrue(a1 != a2)
  expectEqual(identity1, a1._rawIdentifier())
  expectEqual(identity2, a2._rawIdentifier())
}

//===----------------------------------------------------------------------===//
// Index tests
//===----------------------------------------------------------------------===//
public struct ArrayIndexTest<T: Collection> {  
  public enum Operation {
    case append(Int)
    case insert(Int, at: Int)
    case partition(by: (OpaqueValue<Int>) throws -> Bool)
    case removeFirst
    case removeFirstN(Int)
    case removeLast
    case removeLastN(Int)
    case removeAt(Int)
    case removeAll(Bool)
    case removeClosedSubrange(ClosedRange<Int>)
    case removeHalfClosedSubrange(Range<Int>)
  }
  
  public let data: T
  public let expectedStart: Int
  public let expectedEnd: Int
  public let range: Range<Int>?
  public let operation: Operation
  public let loc: SourceLoc

  public init(data: T, expectedStart: Int, expectedEnd: Int, 
        operation: Operation, range: Range<Int>? = nil,
        file: String = #file, line: UInt = #line) {
    self.data = data
    self.expectedStart = expectedStart
    self.expectedEnd = expectedEnd
    self.operation = operation
    self.range = range
    self.loc = SourceLoc(file, line, comment: "Array index test data")
  }
}

let indexTests: [ArrayIndexTest<[Int]>] = [
  // Check how partition() affects indices.
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 1,
    expectedEnd: 2,
    operation: .partition(by: { $0.value > 100 } ),
    range: 1..<2
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 1,
    expectedEnd: 3,
    operation: .partition(by: { $0.value > 0} ),
    range: 1..<3
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 1,
    expectedEnd: 3,
    operation: .partition(by: { $0.value > 3000 }),
    range: 1..<3
  ),
  // Check how partition(by:) affects indices. 
  ArrayIndexTest(
    data: [ 10, 2, -33, 44, -5 ],
    expectedStart: 0,
    expectedEnd: 5,
    operation: .partition(by: { $0.value > 0 })
  ),
  ArrayIndexTest(
    data: [ 10, 2, -33, 44, -5 ],
    expectedStart: 0,
    expectedEnd: 5,
    operation: .partition(by: { $0.value > 100 })
  ),
  // Check how append affects indices.
  ArrayIndexTest(
    data: [ 2 ],
    expectedStart: 0,
    expectedEnd: 2,
    operation: .append(1)
  ),
  ArrayIndexTest(
    data: [],
    expectedStart: 0,
    expectedEnd: 1,
    operation: .append(1)
  ),
  // FIXME: re-enable when rdar://problem/33358110 is addressed
  // ArrayIndexTest(
  //   data: [ 42, 2525, 3535, 42 ],
  //   expectedStart: 1,
  //   expectedEnd: 3,
  //   operation: .append(1),
  //   range: 1..<2
  // ),
  // Check how insert(_:at:) affects indices.
  ArrayIndexTest(
    data: [ 2 ],
    expectedStart: 0,
    expectedEnd: 2,
    operation: .insert(2, at: 0)
  ),
  ArrayIndexTest(
    data: [ 2 ],
    expectedStart: 0,
    expectedEnd: 2,
    operation: .insert(2, at: 1)
  ),
  ArrayIndexTest(
    data: [ 42, 2525, 3535, 42 ],
    expectedStart: 1,
    expectedEnd: 3,
    operation: .insert(2, at: 1),
    range: 1..<2
  ),
  // Check how removeLast() affects indices.
  ArrayIndexTest(
    data: [ 1 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeLast
  ),
  ArrayIndexTest(
    data: [ 1, 2 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeLast
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 1,
    expectedEnd: 1,
    operation: .removeLast,
    range: 1..<2
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 1,
    expectedEnd: 2,
    operation: .removeLast,
    range: 1..<3
  ),
  // Check how remove(at:) affects indices.
  ArrayIndexTest(
    data: [ 1 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeAt(0)
  ),
  ArrayIndexTest(
    data: [ 1, 2 ],
    expectedStart: 0,
    expectedEnd: 1,
    operation: .removeAt(1)
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 1,
    expectedEnd: 1,
    operation: .removeAt(1),
    range: 1..<2
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 1,
    expectedEnd: 2,
    operation: .removeAt(1),
    range: 1..<3
  ),
  // Check how removeAll(keepingCapacity:) affects indices.
  ArrayIndexTest(
    data: [ 1, 2, 3 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeAll(true)
  ),
  ArrayIndexTest(
    data: [ 1, 2 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeAll(false)
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 1,
    expectedEnd: 1,
    operation: .removeAll(true),
    range: 1..<2
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeAll(false),
    range: 1..<2
  ),
  // Check how removeFirst() affects indices.
  ArrayIndexTest(
    data: [ 1 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeFirst
  ),
  ArrayIndexTest(
    data: [ 1, 2 ],
    expectedStart: 0,
    expectedEnd: 1,
    operation: .removeFirst
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 2,
    expectedEnd: 2,
    operation: .removeFirst,
    range: 1..<2
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 2,
    expectedEnd: 3,
    operation: .removeFirst,
    range: 1..<3
  ),
  // Check how removeFirst(_:) affects indices.
  ArrayIndexTest(
    data: [ 1, 2 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeFirstN(2)
  ),
  ArrayIndexTest(
    data: [ 1, 2, 3, 4 ],
    expectedStart: 0,
    expectedEnd: 2,
    operation: .removeFirstN(2)
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 3,
    expectedEnd: 3,
    operation: .removeFirstN(2),
    range: 1..<3
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 3,
    expectedEnd: 4,
    operation: .removeFirstN(2),
    range: 1..<4
  ),
  // Check how removeLast() affects indices.
  ArrayIndexTest(
    data: [ 1 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeLast
  ),
  ArrayIndexTest(
    data: [ 1, 2 ],
    expectedStart: 0,
    expectedEnd: 1,
    operation: .removeLast
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 1,
    expectedEnd: 1,
    operation: .removeLast,
    range: 1..<2
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 1,
    expectedEnd: 1,
    operation: .removeLast,
    range: 1..<2
  ),
  // Check how removeSubrange(_:ClosedRange) affects indices.
  ArrayIndexTest(
    data: [ 1 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeHalfClosedSubrange(0..<1)
  ),
  ArrayIndexTest(
    data: [ 1, 2, 3 ],
    expectedStart: 0,
    expectedEnd: 1,
    operation: .removeHalfClosedSubrange(0..<2)
  ),
  ArrayIndexTest(
    data: [ 1, 2, 3 ],
    expectedStart: 0,
    expectedEnd: 1,
    operation: .removeHalfClosedSubrange(0..<3)
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 1,
    expectedEnd: 1,
    operation: .removeHalfClosedSubrange(1..<2),
    range: 1..<2
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 1,
    expectedEnd: 2,
    operation: .removeHalfClosedSubrange(1..<2),
    range: 1..<3
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99 ],
    expectedStart: 1,
    expectedEnd: 2,
    operation: .removeHalfClosedSubrange(2..<4),
    range: 1..<4
  ),
  // Check how removeSubrange(_:Range) affects indices.
  ArrayIndexTest(
    data: [ 1, 2 ],
    expectedStart: 0,
    expectedEnd: 0,
    operation: .removeClosedSubrange(0...1)
  ),
  ArrayIndexTest(
    data: [ 1, 2, 3 ],
    expectedStart: 0,
    expectedEnd: 1,
    operation: .removeClosedSubrange(0...1)
  ),
  ArrayIndexTest(
    data: [ 1, 2, 3 ],
    expectedStart: 0,
    expectedEnd: 1,
    operation: .removeClosedSubrange(0...2)
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 99 ],
    expectedStart: 1,
    expectedEnd: 1,
    operation: .removeClosedSubrange(1...2),
    range: 1..<3
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99, 44 ],
    expectedStart: 1,
    expectedEnd: 2,
    operation: .removeClosedSubrange(2...3),
    range: 1..<4
  ),
  ArrayIndexTest(
    data: [ 99, 1010, 2020, 99, 44 ],
    expectedStart: 1,
    expectedEnd: 2,
    operation: .removeClosedSubrange(1...2),
    range: 1..<4
  )
]

% for Kind in ['Array', 'ContiguousArray', 'ArraySlice']:
ArrayTestSuite.test("ArrayIndexTests") {
  for test in indexTests {
    let testData = test.data.map(OpaqueValue.init)
% if Kind == 'ArraySlice':
    guard let range = test.range else { continue }
    var a = testData[range]
% else:
    if test.range != nil { continue }
    var a = ${Kind}(testData)
% end

    switch test.operation {
    case let .append(v):
      a.append(OpaqueValue(v))
    case let .insert(v, index):
      a.insert(OpaqueValue(v), at: index)
    case let .partition(c):
      expectDoesNotThrow({ 
        _ = try a.partition(by: c) 
      })
    case .removeFirst:
      a.removeFirst()
    case let .removeFirstN(n):
      a.removeFirst(n)
    case .removeLast:
      a.removeLast()
    case let .removeLastN(n):
      a.removeLast(n)
    case let .removeAt(index):
      a.remove(at: index)
    case let .removeAll(keepCapacity):
      a.removeAll(keepingCapacity: keepCapacity)
    case let .removeHalfClosedSubrange(range):
        a.removeSubrange(range)
    case let .removeClosedSubrange(range):
        a.removeSubrange(range)
    }
    
    expectEqual(test.expectedStart, a.startIndex, stackTrace: SourceLocStack().with(test.loc))
    expectEqual(test.expectedEnd, a.endIndex, stackTrace: SourceLocStack().with(test.loc))
  }
}
% end

//===----------------------------------------------------------------------===//
// Array and EvilCollection that changes its size while we are not looking
//===----------------------------------------------------------------------===//

let evilBoundsError = "EvilCollection: index out of range"

final class EvilSequence : Sequence {
  init(_ growth: Int) {
    self.growth = growth
  }

  var growth: Int
  var _count: Int = 20

  var underestimatedCount: Int {
    defer { _count += growth }
    return _count
  }

  func makeIterator() -> AnyIterator<LifetimeTracked> {
    var i = 0
    return AnyIterator {
      if i >= self._count { return nil }
      let result = LifetimeTracked(i)
      i += 1
      return result
    }
  }
}

final class EvilCollection : Collection {
  func index(after i: Int) -> Int {
    return i + 1
  }

  init(_ growth: Int, boundsChecked: Bool) {
    self.growth = growth
    self.boundsChecked = boundsChecked
  }

  var growth: Int
  var _count: Int = 20
  var boundsChecked: Bool

  var startIndex : Int {
    _count += growth
    return 0
  }

  var endIndex : Int {
    return _count
  }

  subscript(i: Int) -> LifetimeTracked {
    if boundsChecked {
      precondition(i >= 0 && i < _count, evilBoundsError)
    }
    return LifetimeTracked(i)
  }

  // Default implementation will call _failEarlyRangeCheck,
  // passing in a startIndex that will grow _count faster than
  // necessary.
  func formIndex(after i: inout Int) {
    i += 1
  }
}

for (step, evilBoundsCheck) in [ (1, true), (-1, false), (-1, true) ] {

  let message = step < 0 && evilBoundsCheck
    ? evilBoundsError
    : "invalid Collection: count differed in successive traversals"

  let constructionMessage =
    /*_isStdlibInternalChecksEnabled() && !evilBoundsCheck && step <= 0
      ? "_UnsafePartiallyInitializedContiguousArrayBuffer has no more capacity"
      :*/ message

  // The invalid Collection error is a _debugPreconditon that will only fire
  // in a Debug assert configuration.
  let expectedToFail = (step < 0 && evilBoundsCheck) ||
                       _isDebugAssertConfiguration()

  let natureOfEvil = step > 0 ? "Growth" : "Shrinkage"
  let boundsChecked = evilBoundsCheck ? "BoundsChecked" : "NoBoundsCheck"
  let testPrefix = "MemorySafety/\(boundsChecked)/Evil\(natureOfEvil)"

  ArrayTestSuite.test("\(testPrefix)/Infrastructure/EvilSequence") {
    let evil = EvilSequence(step)
    let count0 = evil.underestimatedCount
    let count1 = evil.underestimatedCount
    expectNotEqual(count0, count1)
   if step > 0 {
      expectLE(count0, count1)
    }
    else {
      expectGE(count0, count1)
    }
  }

  let t1 = ArrayTestSuite.test("\(testPrefix)/Infrastructure/EvilCollection")
  (evilBoundsCheck && _isDebugAssertConfiguration()
    ? t1.crashOutputMatches(evilBoundsError) : t1)
  .code {
    let evil = EvilCollection(step, boundsChecked: evilBoundsCheck)
    let count0 = evil.count
    let count1 = evil.count
    expectNotEqual(count0, count1)
   if step > 0 {
      expectLE(count0, count1)
    }
    else {
      expectGE(count0, count1)
    }
    if evilBoundsCheck {
      expectCrashLater()
    }
    let x = evil[-1]
    _blackHole(x)
  }

  let t2 = ArrayTestSuite.test("\(testPrefix)/Construction")
  (_isDebugAssertConfiguration() && expectedToFail
    ? t2.crashOutputMatches(constructionMessage) : t2)
  .code {
    let evil = EvilCollection(step, boundsChecked: evilBoundsCheck)

    if expectedToFail {
      expectCrashLater()
    }

    let a = Array(evil)
    _blackHole(a)
  }

  for (op, rangeMax) in ["Grow":0, "Shrink":200] {
    let t3 =  ArrayTestSuite.test("\(testPrefix)/replaceSubrange/\(op)Unique")
    (_isDebugAssertConfiguration() ? t3.crashOutputMatches(message) : t3)
    .code {
      let evil = EvilCollection(step, boundsChecked: evilBoundsCheck)
      var a = Array((0..<200).lazy.map { LifetimeTracked($0) })
      if expectedToFail {
        expectCrashLater()
      }
      a.replaceSubrange(0..<rangeMax, with: evil)
    }

    let t4 = ArrayTestSuite.test("\(testPrefix)/replaceSubrange/\(op)NonUnique")
    (_isDebugAssertConfiguration() ? t4.crashOutputMatches(message) : t4)
    .code {
      let evil = EvilCollection(step, boundsChecked: evilBoundsCheck)
      var a = Array((0..<200).lazy.map { LifetimeTracked($0) })
      let b = a
      if expectedToFail {
        expectCrashLater()
      }
      a.replaceSubrange(0..<rangeMax, with: evil)
      _blackHole(b)
    }
  }

  ArrayTestSuite.test("\(testPrefix)/SequenceMap")
  .skip(.custom(
    { _isFastAssertConfiguration() },
    reason: "this trap is not guaranteed to happen in -Ounchecked"))
  .code {
    let evil = EvilSequence(step)

    if step < 0 {
      expectCrashLater()
    }
    let a = evil.map { $0 }
    _blackHole(a)
  }

  ArrayTestSuite.test("\(testPrefix)/CollectionMap")
  .code {
    let evil = EvilCollection(step, boundsChecked: evilBoundsCheck)

    if expectedToFail {
      expectCrashLater()
    }

    let a = evil.map { $0 }
    _blackHole(a)
  }

  ArrayTestSuite.test("\(testPrefix)/FilterAll")
  .code {
    let evil = EvilCollection(step, boundsChecked: evilBoundsCheck)

    let a = evil.filter { _ in true }
    _blackHole(a)
  }

  ArrayTestSuite.test("\(testPrefix)/FilterNone")
  .code {
    let evil = EvilCollection(step, boundsChecked: evilBoundsCheck)

    let a = evil.filter { _ in false }
    _blackHole(a)
  }
}

runAllTests()