[stdlib] Convert existential collection === operator to method

Author: natecook1000

stdlib/public/core/ExistentialCollection.swift.gyb

@@ -718,27 +718,25 @@ public func < (lhs: AnyIndex, rhs: AnyIndex) -> Bool {
 /// A protocol for `AnyCollection<Element>`,
 /// `AnyBidirectionalCollection<Element>`, and
 /// `AnyRandomAccessCollection<Element>`.
-///
-/// This protocol can be considered an implementation detail of the
-/// `===` and `!==` implementations for these types.
 public protocol AnyCollectionProtocol : Collection {
   /// Identifies the underlying collection stored by `self`. Instances
   /// copied from one another have the same `_underlyingCollectionID`.
   var _underlyingCollectionID: ObjectIdentifier { get }
-}
 
-/// Returns `true` iff `lhs` and `rhs` store the same underlying collection.
-public func === <
-  L : AnyCollectionProtocol, R : AnyCollectionProtocol
->(lhs: L, rhs: R) -> Bool {
-  return lhs._underlyingCollectionID == rhs._underlyingCollectionID
+  /// Returns `true` iff `self` and `other` use the same `_box` to store their
+  /// underlying collections.
+  func _storesSameUnderlyingCollection<
+    C: AnyCollectionProtocol
+  >(_ other: C) -> Bool
 }
 
-/// Returns `false` iff `lhs` and `rhs` store the same underlying collection.
-public func !== <
-  L : AnyCollectionProtocol, R : AnyCollectionProtocol
->(lhs: L, rhs: R) -> Bool {
-  return lhs._underlyingCollectionID != rhs._underlyingCollectionID
+extension AnyCollectionProtocol {
+  public // @testable
+  func _storesSameUnderlyingCollection<
+    C: AnyCollectionProtocol
+  >(_ other: C) -> Bool {
+    return _underlyingCollectionID == other._underlyingCollectionID
+  }
 }
 
 % for (ti, Traversal) in enumerate(TRAVERSALS):
@@ -1003,3 +1001,17 @@ public func anyGenerator<G : IteratorProtocol>(_ base: G) -> AnyIterator<G.Eleme
 public func anyGenerator<Element>(_ body: () -> Element?) -> AnyIterator<Element> {
   Builtin.unreachable()
 }
+
+@available(*, unavailable)
+public func === <
+  L : AnyCollectionProtocol, R : AnyCollectionProtocol
+>(lhs: L, rhs: R) -> Bool {
+  Builtin.unreachable()
+}
+
+@available(*, unavailable)
+public func !== <
+  L : AnyCollectionProtocol, R : AnyCollectionProtocol
+>(lhs: L, rhs: R) -> Bool {
+  Builtin.unreachable()
+}

validation-test/stdlib/ExistentialCollection.swift.gyb

@@ -357,13 +357,13 @@ tests.test("BidirectionalCollection") {
   let bc0_ = AnyBidirectionalCollection(fc0)  // upgrade!
   expectNotEmpty(bc0_)
   let bc0 = bc0_!
-  expectTrue(fc0 === bc0)
+  expectTrue(fc0._storesSameUnderlyingCollection(bc0))
 
   let fc1 = AnyCollection(a0.lazy.reversed()) // new collection
-  expectFalse(fc1 === fc0)
+  expectFalse(fc1._storesSameUnderlyingCollection(fc0))
 
   let fc2 = AnyCollection(bc0)                // downgrade
-  expectTrue(fc2 === bc0)
+  expectTrue(fc2._storesSameUnderlyingCollection(bc0))
 
   let a1 = ContiguousArray(bc0.lazy.reversed())
   expectEqual(a0, a1)
@@ -381,7 +381,7 @@ tests.test("BidirectionalCollection") {
   let s0 = "Hello, Woyld".characters
   let bc1 = AnyBidirectionalCollection(s0)
   let fc3 = AnyCollection(bc1)
-  expectTrue(fc3 === bc1)
+  expectTrue(fc3._storesSameUnderlyingCollection(bc1))
   expectEmpty(AnyRandomAccessCollection(bc1))
   expectEmpty(AnyRandomAccessCollection(fc3))
 }
@@ -392,13 +392,13 @@ tests.test("RandomAccessCollection") {
   let rc0_ = AnyRandomAccessCollection(fc0)         // upgrade!
   expectNotEmpty(rc0_)
   let rc0 = rc0_!
-  expectTrue(rc0 === fc0)
+  expectTrue(rc0._storesSameUnderlyingCollection(fc0))
 
   let bc1 = AnyBidirectionalCollection(rc0)         // downgrade
-  expectTrue(bc1 === rc0)
+  expectTrue(bc1._storesSameUnderlyingCollection(rc0))
 
   let fc1 = AnyBidirectionalCollection(rc0)         // downgrade
-  expectTrue(fc1 === rc0)
+  expectTrue(fc1._storesSameUnderlyingCollection(rc0))
 
   let a1 = ContiguousArray(rc0.lazy.reversed())
   expectEqual(a0, a1)