Addressing PR comments and updating some tests

Author: Max Moiseev

stdlib/private/StdlibCollectionUnittest/CheckCollectionType.swift.gyb

@@ -561,7 +561,7 @@ extension TestSuite {
       return makeCollectionOfEquatable(elements.map(wrapValueIntoEquatable))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
     //===------------------------------------------------------------------===//
     // generate()
@@ -1209,7 +1209,7 @@ extension TestSuite {
       return makeCollection(elements.map(wrapValue))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
     // FIXME: swift-3-indexing-model - add tests for the follow?
     //          index(before: of i: Index) -> Index
@@ -1522,7 +1522,7 @@ extension TestSuite {
 
     addBidirectionalCollectionTests(${forwardTestArgs})
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
     func makeWrappedCollection(_ elements: [OpaqueValue<Int>]) -> C {
       return makeCollection(elements.map(wrapValue))

stdlib/private/StdlibCollectionUnittest/CheckMutableCollectionType.swift.gyb

@@ -148,7 +148,7 @@ extension TestSuite {
       return makeCollectionOfComparable(elements.map(wrapValueIntoComparable))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
 //===----------------------------------------------------------------------===//
 // subscript(_: Index)
@@ -749,7 +749,7 @@ self.test("\(testNamePrefix).partition/InvalidOrderings") {
       return makeCollection(elements.map(wrapValue))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
 //===----------------------------------------------------------------------===//
 // subscript(_: Index)
@@ -906,7 +906,7 @@ self.test("\(testNamePrefix).partition/DispatchesThrough_withUnsafeMutableBuffer
       return makeCollectionOfComparable(elements.map(wrapValueIntoComparable))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
 //===----------------------------------------------------------------------===//
 // sort()

stdlib/private/StdlibCollectionUnittest/CheckRangeReplaceableCollectionType.swift

@@ -497,7 +497,7 @@ extension TestSuite {
       return makeCollection(elements.map(wrapValue))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
 //===----------------------------------------------------------------------===//
 // init()
@@ -1218,7 +1218,7 @@ self.test("\(testNamePrefix).OperatorPlus") {
       return makeCollection(elements.map(wrapValue))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
 //===----------------------------------------------------------------------===//
 // removeLast()
@@ -1340,7 +1340,7 @@ self.test("\(testNamePrefix).removeLast(n: Int)/whereIndexIsBidirectional/remove
       resiliencyChecks: resiliencyChecks,
       outOfBoundsIndexOffset: outOfBoundsIndexOffset)
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
     // No extra checks for collections with random access traversal so far.
   } // addRangeReplaceableRandomAccessCollectionTests

stdlib/private/StdlibCollectionUnittest/CheckRangeReplaceableSliceType.swift

@@ -65,7 +65,7 @@ extension TestSuite {
       return makeCollection(elements.map(wrapValue))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
     //===------------------------------------------------------------------===//
     // removeFirst()
@@ -210,7 +210,7 @@ extension TestSuite {
       return makeCollection(elements.map(wrapValue))
     }
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
     //===------------------------------------------------------------------===//
     // removeLast()
@@ -351,7 +351,7 @@ extension TestSuite {
       resiliencyChecks: resiliencyChecks,
       outOfBoundsIndexOffset: outOfBoundsIndexOffset)
 
-    testNamePrefix += String(C.Type.self)
+    testNamePrefix += String(describing: C.Type.self)
 
     // No tests yet.
   } // addRangeReplaceableRandomAccessSliceTests

stdlib/private/StdlibCollectionUnittest/CheckSequenceType.swift

@@ -1484,7 +1484,7 @@ extension TestSuite {
       return makeSequenceOfEquatable(elements.map(wrapValueIntoEquatable))
     }
 
-    testNamePrefix += String(S.Type.self)
+    testNamePrefix += String(describing: S.Type.self)
 
     let isMultiPass = makeSequence([])
       ._preprocessingPass { true } ?? false

stdlib/public/core/Integers.swift.gyb

@@ -688,7 +688,7 @@ public protocol SignedInteger_ : BinaryInteger, SignedArithmetic {
 
 extension SignedInteger_ {
   public var description: String {
-    let base = String(magnitude)
+    let base = String(describing: magnitude)
     return self < 0 ? "-" + base : base
   }
 

stdlib/public/core/OutputStream.swift

@@ -164,7 +164,17 @@ public protocol CustomStringConvertible {
   var description: String { get }
 }
 
+/// A type that can be represented as a string in a lossless, unambiguous way.
+///
+/// For example, the integer value 1050 can be represented in its entirety as
+/// the string "1050".
+///
+/// The description property of a conforming type must be a value-preserving
+/// representation of the original value. As such, it should be possible to
+/// attempt to re-create an instance from its string representation.
 public protocol LosslessStringConvertible : CustomStringConvertible {
+  /// Instantiates an instance of the conforming type from a string
+  /// representation.
   init?(_ description: String)
 }
 

stdlib/public/core/StaticString.swift

@@ -255,7 +255,7 @@ public struct StaticString
 
 extension StaticString {
   public var customMirror: Mirror {
-    return Mirror(reflecting: String(describing: self))
+    return Mirror(reflecting: description)
   }
 }
 

stdlib/public/core/String.swift

@@ -982,9 +982,10 @@ extension String {
 #endif
   }
 
-  public // @testable
-  init<T: LosslessStringConvertible>(_ v: T) {
-    self = v.description
+  /// Creates an instance from the description of a given
+  /// LosslessStringConvertible instance.
+  public init<T : LosslessStringConvertible>(_ value: T) {
+    self = value.description
   }
 }
 

stdlib/public/core/UnicodeScalar.swift

@@ -287,9 +287,9 @@ extension UnicodeScalar : LosslessStringConvertible {
     if let v = UInt32(description) where (v < 0xD800 || v > 0xDFFF)
       && v <= 0x10FFFF {
       self = UnicodeScalar(v)
+    } else {
+      return nil
     }
-
-    return nil
   }
 }