[XcodeGen] Pattern match by KeyPath<T, Bool>

Simpler pattern match by `is` properties. E.g. `\.isNewline`

Author: rintaro

utils/swift-xcodegen/Sources/SwiftXcodeGen/Command/CommandParser.swift

@@ -130,7 +130,7 @@ fileprivate extension ByteScanner {
     // Consume the element, stopping at the first space.
     return try consume(using: { consumer in
       switch consumer.peek {
-      case let c where c.isSpaceOrTab:
+      case \.isSpaceOrTab:
         return false
       case "\"":
         try consumer.consumeStringLiteral()

utils/swift-xcodegen/Sources/SwiftXcodeGen/Ninja/NinjaParser.swift

@@ -46,13 +46,11 @@ fileprivate extension ByteScanner {
       // Ninja uses '$' as the escape character.
       if c == "$" {
         switch consumer.peek(ahead: 1) {
-        case let c? where c.isSpaceOrTab:
-          fallthrough
-        case "$", ":":
+        case "$", ":", \.isSpaceOrTab:
           // Skip the '$' and take the unescaped character.
           consumer.skip()
           return consumer.eat()
-        case let c? where c.isNewline:
+        case \.isNewline:
           // This is a line continuation, skip the newline, and strip any
           // following space.
           consumer.skip(untilAfter: \.isNewline)
@@ -160,7 +158,7 @@ extension NinjaParser.Lexer {
   private mutating func consumeElement() -> String? {
     input.consumeUnescaped(while: { char in
       switch char {
-      case let c where c.isNinjaOperator || c.isSpaceTabOrNewline:
+      case \.isNinjaOperator, \.isSpaceTabOrNewline:
         false
       default:
         true

utils/swift-xcodegen/Sources/SwiftXcodeGen/Scanner/Byte.swift

@@ -29,18 +29,6 @@ extension Byte: Comparable {
   }
 }
 
-extension Byte? {
-  var isSpaceOrTab: Bool {
-    self?.isSpaceOrTab == true
-  }
-  var isNewline: Bool {
-    self?.isNewline == true
-  }
-  var isSpaceTabOrNewline: Bool {
-    self?.isSpaceTabOrNewline == true
-  }
-}
-
 extension Byte {
   var isSpaceOrTab: Bool {
     self == " " || self == "\t"

utils/swift-xcodegen/Sources/SwiftXcodeGen/Utils.swift

@@ -132,3 +132,12 @@ extension String {
     }
   }
 }
+
+/// Pattern match by `is` property. E.g. `case \.isNewline: ...`
+func ~= <T>(keyPath: KeyPath<T, Bool>, subject: T) -> Bool {
+  return subject[keyPath: keyPath]
+}
+
+func ~= <T>(keyPath: KeyPath<T, Bool>, subject: T?) -> Bool {
+  return subject?[keyPath: keyPath] == true
+}