Drop support for swift language version 4.0

Author: hartbit

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:4.0
+// swift-tools-version:4.2
 
 /*
  This source file is part of the Swift.org open source project
@@ -239,7 +239,7 @@ let package = Package(
  name: "XcodeprojTests",
  dependencies: ["Xcodeproj", "TestSupport"]),
  ],
- swiftLanguageVersions: [4]
+ swiftLanguageVersions: [.v4_2]
 )
 
 // Add package dependency on llbuild when not bootstrapping.

Sources/Basic/ByteString.swift

@@ -90,18 +90,6 @@ extension ByteString: CustomStringConvertible {
  }
 }
 
-#if !swift(>=4.2)
-extension ByteString {
- public var hashValue: Int {
- var result = contents.count
- for byte in contents {
- result = result &* 31 &+ Int(byte)
- }
- return result
- }
-}
-#endif
-
 /// ByteStreamable conformance for a ByteString.
 extension ByteString: ByteStreamable {
  public func write(to stream: OutputByteStream) {

Sources/Utility/Version.swift

@@ -45,21 +45,6 @@ public struct Version: Hashable {
  }
 }
 
-#if !swift(>=4.2)
-extension Version {
- public var hashValue: Int {
- let mul: UInt64 = 0x9ddfea08eb382d69
- var result: UInt64 = 0
- result = (result &* mul) ^ UInt64(bitPattern: Int64(major.hashValue))
- result = (result &* mul) ^ UInt64(bitPattern: Int64(minor.hashValue))
- result = (result &* mul) ^ UInt64(bitPattern: Int64(patch.hashValue))
- result = prereleaseIdentifiers.reduce(result, { ($0 &* mul) ^ UInt64(bitPattern: Int64($1.hashValue)) })
- result = buildMetadataIdentifiers.reduce(result, { ($0 &* mul) ^ UInt64(bitPattern: Int64($1.hashValue)) })
- return Int(truncatingIfNeeded: result)
- }
-}
-#endif
-
 extension Version: Comparable {
 
  func isEqualWithoutPrerelease(_ other: Version) -> Bool {