Porting String APIs to Subtring and fixing some tests

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