Porting String APIs to Subtring and fixing some tests

stdlib/private/StdlibUnittest/StdlibUnittest.swift.gyb

@@ -158,6 +158,18 @@ public func expectEqual<T : Equatable, U : Equatable, V : Equatable, W : Equatab
   expectEqualTest(expected.3, actual.3, ${trace}, showFrame: false) {$0 == $1}
 }
 
+% for (Lhs, Rhs) in [('String', 'Substring'), ('Substring', 'String')]:
+public func expectEqual(_ expected: ${Lhs}, _ actual: ${Rhs}, ${TRACE}) {
+  if !(expected == actual) {
+    expectationFailure(
+      "expected: \(String(reflecting: expected)) (of type \(String(reflecting: type(of: expected))))\n"
+      + "actual: \(String(reflecting: actual)) (of type \(String(reflecting: type(of: actual))))",
+      trace: ${trace}
+    )
+  }
+}
+% end
+
 public func expectEqualReference(_ expected: AnyObject?, _ actual: AnyObject?, ${TRACE}) {
   expectEqualTest(expected, actual, ${trace}, showFrame: false) {$0 === $1}
 }

stdlib/public/core/CMakeLists.txt

@@ -127,6 +127,7 @@ set(SWIFTLIB_ESSENTIAL
   StringUnicodeScalarView.swift
   StringUTF16.swift
   StringUTF8.swift
+  Substring.swift.gyb
   SwiftNativeNSArray.swift
   UnavailableStringAPIs.swift.gyb
   Unicode.swift

stdlib/public/core/GroupInfo.json

@@ -21,6 +21,7 @@
     "StringUTF16.swift",
     "StringUTF8.swift",
     "StringUnicodeScalarView.swift",
+    "Substring.swift",
     "Unicode.swift",
     "UnicodeScalar.swift",
     "UnicodeTrie.swift",

stdlib/public/core/StringRangeReplaceableCollection.swift.gyb

@@ -10,98 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-public struct Substring : RangeReplaceableCollection {
-  public typealias Index = String.CharacterView.Index
-  public typealias IndexDistance = String.CharacterView.IndexDistance
-
-  internal let base: String
-  internal var bounds: Range<Index>
-
-
-  public init() {
-    let s = ""
-    self.init(s, s.startIndex..<s.endIndex)
-  }
-
-  internal init(_ base: String, _ bounds: Range<Index>) {
-    self.base = base
-    self.bounds = bounds
-  }
-
-  internal init(_ base: String, _ bounds: ClosedRange<Index>) {
-    self.init(base, base._makeHalfOpen(bounds))
-  }
-
-  public var startIndex: Index { return bounds.lowerBound }
-
-  public var endIndex: Index { return bounds.upperBound }
-
-  public func index(after i: Index) -> Index {
-    _precondition(i < bounds.upperBound, "Cannot increment beyond endIndex")
-    _precondition(i >= bounds.lowerBound, "Cannot increment beyond startIndex")
-    return base.characters.index(after: i)
-  }
-
-  // TODO: swift-3-indexing-model - add docs
-  public func index(before i: Index) -> Index {
-    _precondition(i <= bounds.upperBound, "Cannot decrement an invalid index")
-    _precondition(i > bounds.lowerBound, "Cannot decrement beyond startIndex")
-    return base.characters.index(before: i)
-  }
-
-  public func index(_ i: Index, offsetBy n: IndexDistance) -> Index {
-    let result = base.characters.index(i, offsetBy: n)
-    _precondition(bounds.contains(result),
-      "Operation results in an invalid index")
-    return result
-  }
-
-  public func index(
-    _ i: Index, offsetBy n: IndexDistance, limitedBy limit: Index
-  ) -> Index? {
-    let result =  base.characters.index(i, offsetBy: n, limitedBy: limit)
-    _precondition(result.map { bounds.contains($0) } ?? true,
-      "Operation results in an invalid index")
-    return result
-  }
-
-  public func distance(from start: Index, to end: Index) -> IndexDistance {
-    return base.characters.distance(from: start, to: end)
-  }
-
-  public subscript(i: Index) -> Character {
-    _precondition(bounds.contains(i), "Invalid index")
-    return base.characters[i]
-  }
-
-  public subscript(bounds: Range<Index>) -> Substring {
-    // FIXME(strings): add checks
-    return Substring(base, bounds)
-  }
-
-  public subscript(bounds: ClosedRange<Index>) -> Substring {
-    // FIXME(strings): add checks
-    return Substring(base, bounds)
-  }
-
-% for Range in ['Range', 'ClosedRange']:
-
-  public mutating func replaceSubrange<C>(
-    _ bounds: ${Range}<Index>,
-    with newElements: C
-  ) where C : Collection, C.Iterator.Element == Character {
-    fatalError()
-  }
-
-  public mutating func replaceSubrange(
-    _ bounds: ${Range}<Index>, with newElements: Substring
-  ) {
-    replaceSubrange(bounds, with: newElements.base.characters)
-  }
-
-% end
-}
-
 extension String : RangeReplaceableCollection, BidirectionalCollection {
   /// The index type for subscripting a string.
   public typealias Index = CharacterView.Index

stdlib/public/core/Substring.swift.gyb

@@ -0,0 +1,207 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+public struct Substring : RangeReplaceableCollection {
+  public typealias Index = String.CharacterView.Index
+  public typealias IndexDistance = String.CharacterView.IndexDistance
+
+  public let base: String
+  public internal(set) var bounds: Range<Index>
+
+
+  public init() {
+    let s = ""
+    self.init(s, s.startIndex..<s.endIndex)
+  }
+
+  internal init(_ base: String, _ bounds: Range<Index>) {
+    self.base = base
+    self.bounds = bounds
+  }
+
+  internal init(_ base: String, _ bounds: ClosedRange<Index>) {
+    self.init(base, base._makeHalfOpen(bounds))
+  }
+
+  public var startIndex: Index { return bounds.lowerBound }
+
+  public var endIndex: Index { return bounds.upperBound }
+
+  public func index(after i: Index) -> Index {
+    _precondition(i < bounds.upperBound, "Cannot increment beyond endIndex")
+    _precondition(i >= bounds.lowerBound, "Cannot increment beyond startIndex")
+    return base.characters.index(after: i)
+  }
+
+  // TODO: swift-3-indexing-model - add docs
+  public func index(before i: Index) -> Index {
+    _precondition(i <= bounds.upperBound, "Cannot decrement an invalid index")
+    _precondition(i > bounds.lowerBound, "Cannot decrement beyond startIndex")
+    return base.characters.index(before: i)
+  }
+
+  public func index(_ i: Index, offsetBy n: IndexDistance) -> Index {
+    let result = base.characters.index(i, offsetBy: n)
+    _precondition(bounds.contains(result),
+      "Operation results in an invalid index")
+    return result
+  }
+
+  public func index(
+    _ i: Index, offsetBy n: IndexDistance, limitedBy limit: Index
+  ) -> Index? {
+    let result =  base.characters.index(i, offsetBy: n, limitedBy: limit)
+    _precondition(result.map { bounds.contains($0) } ?? true,
+      "Operation results in an invalid index")
+    return result
+  }
+
+  public func distance(from start: Index, to end: Index) -> IndexDistance {
+    return base.characters.distance(from: start, to: end)
+  }
+
+  public subscript(i: Index) -> Character {
+    _precondition(bounds.contains(i), "Invalid index")
+    return base.characters[i]
+  }
+
+  public subscript(bounds: Range<Index>) -> Substring {
+    // FIXME(strings): add checks
+    return Substring(base, bounds)
+  }
+
+  public subscript(bounds: ClosedRange<Index>) -> Substring {
+    // FIXME(strings): add checks
+    return Substring(base, bounds)
+  }
+
+
+  public mutating func replaceSubrange<C>(
+    _ bounds: Range<Index>,
+    with newElements: C
+  ) where C : Collection, C.Iterator.Element == Iterator.Element {
+    fatalError()
+  }
+
+% for Range in ['Range', 'ClosedRange']:
+
+  public mutating func replaceSubrange(
+    _ bounds: ${Range}<Index>, with newElements: Substring
+  ) {
+    replaceSubrange(bounds, with: newElements.base.characters)
+  }
+
+% end
+}
+
+
+extension Substring : CustomReflectable {
+  public var customMirror: Mirror {
+    return String(self).customMirror
+  }
+}
+
+extension Substring : CustomPlaygroundQuickLookable {
+  public var customPlaygroundQuickLook: PlaygroundQuickLook {
+    return String(self).customPlaygroundQuickLook
+  }
+}
+
+extension Substring : CustomStringConvertible {
+  public var description: String {
+    return String(self)
+  }
+}
+
+extension Substring : LosslessStringConvertible {
+  public init?(_ description: String) {
+    self.init(description, description.startIndex ..< description.endIndex)
+  }
+}
+
+extension Substring : Equatable {
+  public static func ==(lhs: Substring, rhs: Substring) -> Bool {
+    return String(lhs) == String(rhs)
+  }
+
+  // These are not Equatable requirements, but sufficiently similar to be in
+  // this extension.
+  // FIXME(strings): should be gone if/when an implicit conversion from/to
+  // String is available.
+  // FIXME(ABI):
+  public static func ==(lhs: String, rhs: Substring) -> Bool {
+    return lhs == String(rhs)
+  }
+
+  public static func ==(lhs: Substring, rhs: String) -> Bool {
+    return String(lhs) == rhs
+  }
+
+  public static func !=(lhs: String, rhs: Substring) -> Bool {
+    return lhs != String(rhs)
+  }
+
+  public static func !=(lhs: Substring, rhs: String) -> Bool {
+    return String(lhs) != rhs
+  }
+}
+
+extension Substring : Comparable {
+  public static func <(lhs: Substring, rhs: Substring) -> Bool {
+    return String(lhs) < String(rhs)
+  }
+}
+
+extension Substring : Hashable {
+  public var hashValue : Int {
+    return String(self).hashValue
+  }
+}
+
+extension Substring {
+% for (property, ViewPrefix) in [
+%   ('utf8', 'UTF8'),
+%   ('utf16', 'UTF16'),
+%   ('unicodeScalars', 'UnicodeScalar')]:
+  public typealias ${ViewPrefix}Index = String.${ViewPrefix}View.Index
+
+  public var ${property}: String.${ViewPrefix}View {
+    get {
+      return String(self).${property}
+    }
+    set {
+      let base = String(describing: newValue)
+      self = Substring(base, base.startIndex ..< base.endIndex)
+    }
+  }
+% end
+}
+
+extension Substring {
+  public func hasPrefix(_ prefix: String) -> Bool {
+    return String(self).hasPrefix(prefix)
+  }
+
+  public func hasSuffix(_ suffix: String) -> Bool {
+    return String(self).hasSuffix(suffix)
+  }
+}
+
+extension Substring {
+  public func lowercased() -> String {
+    return String(self).lowercased()
+  }
+
+  public func uppercased() -> String {
+    return String(self).uppercased()
+  }
+}

test/stdlib/NSStringAPI.swift

@@ -530,8 +530,8 @@ NSStringAPIs.test("enumerateLinguisticTagsIn(_:scheme:options:orthography:_:") {
     (tag: String, tokenRange: Range<String.Index>, sentenceRange: Range<String.Index>, stop: inout Bool)
   in
     tags.append(tag)
-    tokens.append(s[tokenRange])
-    sentences.append(s[sentenceRange])
+    tokens.append(String(s[tokenRange]))
+    sentences.append(String(s[sentenceRange]))
     if tags.count == 3 {
       stop = true
     }
@@ -540,7 +540,7 @@ NSStringAPIs.test("enumerateLinguisticTagsIn(_:scheme:options:orthography:_:") {
     [NSLinguisticTagWord, NSLinguisticTagWhitespace, NSLinguisticTagWord],
     tags)
   expectEqual(["Глокая", " ", "куздра"], tokens)
-  let sentence = s[startIndex..<endIndex]
+  let sentence = String(s[startIndex..<endIndex])
   expectEqual([sentence, sentence, sentence], sentences)
 }
 
@@ -550,14 +550,16 @@ NSStringAPIs.test("enumerateSubstringsIn(_:options:_:)") {
   let endIndex = s.index(s.startIndex, offsetBy: 5)
   do {
     var substrings: [String] = []
+    // FIXME(strings): this API should probably change to accept a Substring?
+    // instead of a String? and a range.
     s.enumerateSubstrings(in: startIndex..<endIndex,
       options: String.EnumerationOptions.byComposedCharacterSequences) {
       (substring: String?, substringRange: Range<String.Index>,
        enclosingRange: Range<String.Index>, stop: inout Bool)
     in
       substrings.append(substring!)
-      expectEqual(substring, s[substringRange])
-      expectEqual(substring, s[enclosingRange])
+      expectEqual(substring, String(s[substringRange]))
+      expectEqual(substring, String(s[enclosingRange]))
     }
     expectEqual(["\u{304b}\u{3099}", "お", "☺️", "😀"], substrings)
   }
@@ -569,7 +571,7 @@ NSStringAPIs.test("enumerateSubstringsIn(_:options:_:)") {
        enclosingRange: Range<String.Index>, stop: inout Bool)
     in
       expectNil(substring_)
-      let substring = s[substringRange]
+      let substring = String(s[substringRange])
       substrings.append(substring)
       expectEqual(substring, s[enclosingRange])
     }
@@ -873,7 +875,7 @@ NSStringAPIs.test("linguisticTagsIn(_:scheme:options:orthography:tokenRanges:)")
     [NSLinguisticTagWord, NSLinguisticTagWhitespace, NSLinguisticTagWord],
     tags)
   expectEqual(["Глокая", " ", "куздра"],
-      tokenRanges.map { s[$0] } )
+      tokenRanges.map { String(s[$0]) } )
 }
 
 NSStringAPIs.test("localizedCaseInsensitiveCompare(_:)") {