fix: adds missing return statements

so the project builds without any compile errors on macOS high sierra (10.13.x)

alt-tab-macos/logic/Preferences.swift

@@ -99,11 +99,11 @@ class Preferences {
     }
 
     private static func preferencesVersion(_ url: URL) throws -> Int {
-        try Int(loadFromDisk(url)["version"] ?? "0").orThrow()
+        return try Int(loadFromDisk(url)["version"] ?? "0").orThrow()
     }
 
     private static func loadFromDisk(_ url: URL) throws -> [String: String] {
-        try JSONDecoder().decode([String: String].self, from: Data(contentsOf: url))
+        return try JSONDecoder().decode([String: String].self, from: Data(contentsOf: url))
     }
 
     private static func handleNoFileOrOldFile(_ userFile: URL) throws {
@@ -132,7 +132,7 @@ class Preferences {
     }
 
     private static func fileFromPreferencesFolder(_ fileName: String) -> URL {
-        FileManager.default
+        return FileManager.default
                 .urls(for: .libraryDirectory, in: .userDomainMask)
                 .first!
                 .appendingPathComponent("Preferences", isDirectory: true)

alt-tab-macos/logic/WindowManager.swift

@@ -17,7 +17,7 @@ class OpenWindow {
     }
 
     func computeIcon() -> NSImage? {
-        NSRunningApplication(processIdentifier: ownerPid!)?.icon
+        return NSRunningApplication(processIdentifier: ownerPid!)?.icon
     }
 
     func computeThumbnail() -> NSImage {

alt-tab-macos/ui/Application.swift

@@ -91,7 +91,7 @@ class Application: NSApplication, NSApplicationDelegate, NSWindowDelegate {
     }
 
     func cellWithStep(_ step: Int) -> Int {
-        selectedOpenWindow + step < 0 ? openWindows.count - 1 : (selectedOpenWindow + step) % openWindows.count
+        return selectedOpenWindow + step < 0 ? openWindows.count - 1 : (selectedOpenWindow + step) % openWindows.count
     }
 
     func cycleSelection(_ step: Int) {
@@ -130,6 +130,6 @@ class Application: NSApplication, NSApplicationDelegate, NSWindowDelegate {
     }
 
     func currentlySelectedWindow() -> OpenWindow? {
-        openWindows.count > selectedOpenWindow ? openWindows[selectedOpenWindow] : nil
+        return openWindows.count > selectedOpenWindow ? openWindows[selectedOpenWindow] : nil
     }
 }

alt-tab-macos/ui/PreferencesPanel.swift

@@ -25,7 +25,7 @@ class PreferencesPanel: NSPanel, NSTextViewDelegate {
     }
 
     private func makeLabelsAndInputs() -> [[NSView]] {
-        [
+        return [
             makeLabelWithDropdown(\PreferencesPanel.theme, "Main window theme", "theme", Preferences.themeMacro.labels),
             makeLabelWithDropdown(\PreferencesPanel.metaKey, "Meta key to activate the app", "metaKey", Preferences.metaKeyMacro.labels),
             makeLabelWithInput(\PreferencesPanel.tabKeyCode, "Tab key (NSEvent.keyCode)", "tabKeyCode"),

alt-tab-macos/ui/ThumbnailsPanel.swift

@@ -58,7 +58,7 @@ class ThumbnailsPanel: NSPanel, NSCollectionViewDataSource, NSCollectionViewDele
 
     func collectionView(_ collectionView: NSCollectionView, numberOfItemsInSection section: Int) -> Int {
 //        debugPrint("collectionView: count items", openWindows.count)
-        application!.openWindows.count
+        return application!.openWindows.count
     }
 
     func collectionView(_ collectionView: NSCollectionView, itemForRepresentedObjectAt indexPath: IndexPath) -> NSCollectionViewItem {