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SR-7266: Avoid nesting of ReversedCollection #15815

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Merged
merged 3 commits into from
Apr 12, 2018
Merged

SR-7266: Avoid nesting of ReversedCollection #15815

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b859cdc
SR-7266: Avoid nesting of ReversedCollection
Moximillian Apr 7, 2018
9c13a27
[stdlib] SR-7266 Add ReverseCompatibility test
danielctull Apr 1, 2018
4714952
[stdlib] SR-7266 Make sure to actually run the tests
danielctull Apr 10, 2018
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15 changes: 12 additions & 3 deletions stdlib/public/core/Reverse.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -49,8 +49,6 @@ extension MutableCollection where Self: BidirectionalCollection {
/// * `c.reversed()` does not create new storage
/// * `c.reversed().map(f)` maps eagerly and returns a new array
/// * `c.lazy.reversed().map(f)` maps lazily and returns a `LazyMapCollection`
///
/// - See also: `ReversedRandomAccessCollection`
@_fixed_layout
public struct ReversedCollection<Base: BidirectionalCollection> {
public let _base: Base
Expand Down Expand Up @@ -84,7 +82,7 @@ extension ReversedCollection {
}
}
}

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nitpick: Unnecessary space at the end of the line?

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so my change removes the unnecessary space from that line. Or would you rather not have those kind of cleanups in this PR?

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Oh. I misinterpreted the diff. I would prefer to not mix the cleanups with functional changes, but am guilty of doing it every now and then myself. So let's keep it.

extension ReversedCollection.Iterator: IteratorProtocol, Sequence {
public typealias Element = Base.Element

Expand Down Expand Up @@ -253,6 +251,17 @@ extension ReversedCollection: BidirectionalCollection {

extension ReversedCollection: RandomAccessCollection where Base: RandomAccessCollection { }

extension ReversedCollection {
/// Reversing a reversed collection returns the original collection.
///
/// - Complexity: O(1)
@inlinable
@available(swift, introduced: 4.2)
public func reversed() -> Base {
return _base
}
}

extension BidirectionalCollection {
/// Returns a view presenting the elements of the collection in reverse
/// order.
Expand Down
36 changes: 36 additions & 0 deletions test/stdlib/ReverseCompatibility.swift
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@@ -0,0 +1,36 @@
// RUN: %empty-directory(%t)
// RUN: %target-build-swift %s -o %t/a.out3 -swift-version 3 && %target-run %t/a.out3
// RUN: %target-build-swift %s -o %t/a.out4 -swift-version 4 && %target-run %t/a.out4
// RUN: %target-build-swift %s -o %t/a.out5 -swift-version 5 && %target-run %t/a.out5
// REQUIRES: executable_test

import StdlibUnittest

#if swift(>=4.2)
let swiftVersion = ">=4.2"
#else
let swiftVersion = "<4.2"
#endif

let tests = TestSuite("ReverseCompatibility")

tests.test("Double reverse type/Collection/\(swiftVersion)") {
func reverse<C : BidirectionalCollection>(_ xs: C) {
var result = xs.reversed().reversed()
#if swift(>=4.2)
expectType(C.self, &result)
#else
expectType(ReversedCollection<ReversedCollection<C>>.self, &result)
#endif
}
reverse(Array(0..<10))

func backwardCompatible<C : BidirectionalCollection>(_ xs: C) {
typealias ExpectedType = ReversedCollection<ReversedCollection<C>>
var result: ExpectedType = xs.reversed().reversed()
expectType(ExpectedType.self, &result)
}
backwardCompatible(Array(0..<10))
}

runAllTests()