[stdlib][swift-3-indexing-model] fixing the ReversedCollection/lazy test

Author: Max Moiseev

stdlib/private/StdlibCollectionUnittest/CheckCollectionInstance.swift.gyb

@@ -455,10 +455,6 @@ public func check${Traversal}Collection<
   C.Iterator.Element == ${Element},
   C.Indices.Iterator.Element == C.Index,
   ${Element} : Equatable
-%     if Traversal == 'RandomAccess':
-  , C.Index : Strideable
-  , C.Index.Stride == C.IndexDistance
-%     end
 >(
   _ expected: ${Expected}, _ collection: C,
   ${TRACE},

stdlib/public/core/ClosedRange.swift

@@ -27,6 +27,9 @@ internal enum _ClosedRangeIndexRepresentation<
 public struct ClosedRangeIndex<
   // WORKAROUND rdar://25214598 - should be Bound : Strideable
   Bound : Comparable where Bound : _Strideable, Bound.Stride : Integer
+  // swift-3-indexing-model: should conform to _Strideable, otherwise
+  // CountableClosedRange is not interchangeable with CountableRange in all
+  // contexts.
 > : Comparable {
   /// Creates the past-the-end position.
   internal init() { _value = .pastEnd }

validation-test/stdlib/Lazy.swift.gyb

@@ -753,8 +753,7 @@ tests.test("ReversedCollection/Lazy") {
     var calls = 0
     let reversedAndMapped = reversed.map { (x) -> Int in calls += 1; return x }
     expectEqual(0, calls)
-    // FIXME: swift-3-indexing-model: should be checkRandomAccessCollection(0...11, reversedAndMapped)
-    checkBidirectionalCollection(0...11, reversedAndMapped)
+    checkRandomAccessCollection(0...11, reversedAndMapped)
     expectNotEqual(0, calls)
   }