diff --git a/OptionParse.xcodeproj/project.pbxproj b/OptionParse.xcodeproj/project.pbxproj
index ff2f6b6..5371973 100644
--- a/OptionParse.xcodeproj/project.pbxproj
+++ b/OptionParse.xcodeproj/project.pbxproj
@@ -214,12 +214,12 @@
 			isa = PBXProject;
 			attributes = {
 				LastSwiftUpdateCheck = 0730;
-				LastUpgradeCheck = 0800;
+				LastUpgradeCheck = 0930;
 				ORGANIZATIONNAME = "Steve Marquis";
 				TargetAttributes = {
 					AA1BF11B1D543CB100BD82D4 = {
 						CreatedOnToolsVersion = 7.3.1;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0930;
 					};
 					AA1BF1251D543CB100BD82D4 = {
 						CreatedOnToolsVersion = 7.3.1;
@@ -327,14 +327,22 @@
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
 				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
 				CLANG_WARN_SUSPICIOUS_MOVE = YES;
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
@@ -378,14 +386,22 @@
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
 				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
 				CLANG_WARN_SUSPICIOUS_MOVE = YES;
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
@@ -430,7 +446,7 @@
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SKIP_INSTALL = YES;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -450,7 +466,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = com.BobDevil.OptionParse;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SKIP_INSTALL = YES;
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
diff --git a/OptionParse.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist b/OptionParse.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
new file mode 100644
index 0000000..18d9810
--- /dev/null
+++ b/OptionParse.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>
diff --git a/OptionParse.xcodeproj/xcshareddata/xcschemes/OptionParse.xcscheme b/OptionParse.xcodeproj/xcshareddata/xcschemes/OptionParse.xcscheme
index ca3831f..038b23a 100644
--- a/OptionParse.xcodeproj/xcshareddata/xcschemes/OptionParse.xcscheme
+++ b/OptionParse.xcodeproj/xcshareddata/xcschemes/OptionParse.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0800"
+   LastUpgradeVersion = "0930"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
diff --git a/OptionParse/OptionParser.swift b/OptionParse/OptionParser.swift
index 00b1f3a..fc11cad 100644
--- a/OptionParse/OptionParser.swift
+++ b/OptionParse/OptionParser.swift
@@ -75,11 +75,11 @@ public struct OptionParser {
         case argument(String)
         
         init(_ str: String) {
-            if str.hasPrefix("--") && str.characters.count > 2 {
-                let value = str.substring(from: str.characters.index(str.startIndex, offsetBy: 2))
+            if str.hasPrefix("--") && str.count > 2 {
+                let value = String(str[str.index(str.startIndex, offsetBy: 2)...])
                 self = .name(value)
-            } else if str.hasPrefix("-") && str.characters.count == 2 {
-                self = .shortName(str.characters.last!)
+            } else if str.hasPrefix("-") && str.count == 2 {
+                self = .shortName(str.last!)
             } else {
                 self = .argument(str)
             }
@@ -246,15 +246,15 @@ extension String {
     func terminalWidthLines(withTabDepth tabDepth: Int) -> String {
         var remainingString = self
         var lines: [String] = []
-        while remainingString.characters.count > 80 {
-            guard let range = remainingString.rangeOfCharacter(from: CharacterSet.whitespaces, options: .backwards, range: remainingString.startIndex..<remainingString.characters.index(remainingString.startIndex, offsetBy: 80)) else {
+        while remainingString.count > 80 {
+            guard let range = remainingString.rangeOfCharacter(from: CharacterSet.whitespaces, options: .backwards, range: remainingString.startIndex..<remainingString.index(remainingString.startIndex, offsetBy: 80)) else {
                 lines.append(remainingString)
                 remainingString = ""
                 break
             }
 
-            lines.append(remainingString.substring(to: range.lowerBound))
-            remainingString = remainingString.substring(from: range.upperBound)
+            lines.append(String(remainingString[..<range.lowerBound]))
+            remainingString = String(remainingString[range.upperBound...])
         }
 
         if !remainingString.isEmpty {