Migrate to Swift 4

Author: ikesyo

Package.swift

@@ -16,5 +16,5 @@ let package = Package(
         .target(name: "ReactiveTask", dependencies: ["Result", "ReactiveSwift"], path: "Sources"),
         .testTarget(name: "ReactiveTaskTests", dependencies: ["ReactiveTask", "Quick", "Nimble"]),
     ],
-    swiftLanguageVersions: [3]
+    swiftLanguageVersions: [4]
 )

ReactiveTask.xcodeproj/project.pbxproj

@@ -370,7 +370,8 @@
 				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = macosx;
-				SWIFT_VERSION = 2.3;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Off;
+				SWIFT_VERSION = 4.0;
 				VERSIONING_SYSTEM = "apple-generic";
 				VERSION_INFO_PREFIX = "";
 			};
@@ -390,7 +391,8 @@
 				GCC_NO_COMMON_BLOCKS = YES;
 				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				SDKROOT = macosx;
-				SWIFT_VERSION = 2.3;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Off;
+				SWIFT_VERSION = 4.0;
 				VERSIONING_SYSTEM = "apple-generic";
 				VERSION_INFO_PREFIX = "";
 			};
@@ -406,7 +408,6 @@
 				INFOPLIST_FILE = Sources/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.carthage.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
 			};
 			name = Debug;
 		};
@@ -420,7 +421,6 @@
 				INFOPLIST_FILE = Sources/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.carthage.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
 			};
 			name = Release;
 		};
@@ -435,7 +435,6 @@
 				INFOPLIST_FILE = Tests/ReactiveTaskTests/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.carthage.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
 			};
 			name = Debug;
 		};
@@ -450,7 +449,6 @@
 				INFOPLIST_FILE = Tests/ReactiveTaskTests/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.carthage.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
 			};
 			name = Release;
 		};
@@ -468,7 +466,8 @@
 				GCC_NO_COMMON_BLOCKS = YES;
 				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				SDKROOT = macosx;
-				SWIFT_VERSION = 2.3;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Off;
+				SWIFT_VERSION = 4.0;
 				VERSIONING_SYSTEM = "apple-generic";
 				VERSION_INFO_PREFIX = "";
 			};
@@ -484,7 +483,6 @@
 				INFOPLIST_FILE = Sources/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.carthage.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
 			};
 			name = Test;
 		};
@@ -499,7 +497,6 @@
 				INFOPLIST_FILE = Tests/ReactiveTaskTests/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.carthage.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
 			};
 			name = Test;
 		};
@@ -517,7 +514,8 @@
 				GCC_NO_COMMON_BLOCKS = YES;
 				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				SDKROOT = macosx;
-				SWIFT_VERSION = 2.3;
+				SWIFT_SWIFT3_OBJC_INFERENCE = Off;
+				SWIFT_VERSION = 4.0;
 				VERSIONING_SYSTEM = "apple-generic";
 				VERSION_INFO_PREFIX = "";
 			};
@@ -533,7 +531,6 @@
 				INFOPLIST_FILE = Sources/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.carthage.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
 			};
 			name = Profile;
 		};
@@ -548,7 +545,6 @@
 				INFOPLIST_FILE = Tests/ReactiveTaskTests/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.carthage.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 3.0;
 			};
 			name = Profile;
 		};