Throw error FileManager.default.createFile if returns false

Returning `false` indicates that file creation failed, which we should note instead of ignoring it.

This fixes a warning on Linux that the result of `createFile` was ignored.

Author: ahoppen

Sources/Diagnose/DiagnoseCommand.swift

@@ -213,7 +213,9 @@ package struct DiagnoseCommand: AsyncParsableCommand {
     #if os(macOS)
     reportProgress(.collectingLogMessages(progress: 0), message: "Collecting log messages")
     let outputFileUrl = bundlePath.appendingPathComponent("log.txt")
-    FileManager.default.createFile(atPath: outputFileUrl.path, contents: nil)
+    guard FileManager.default.createFile(atPath: outputFileUrl.path, contents: nil) else {
+      throw ReductionError("Failed to create log.txt")
+    }
     let fileHandle = try FileHandle(forWritingTo: outputFileUrl)
     var bytesCollected = 0
     // 50 MB is an average log size collected by sourcekit-lsp diagnose.
@@ -304,7 +306,9 @@ package struct DiagnoseCommand: AsyncParsableCommand {
   @MainActor
   private func addSwiftVersion(toBundle bundlePath: URL) async throws {
     let outputFileUrl = bundlePath.appendingPathComponent("swift-versions.txt")
-    FileManager.default.createFile(atPath: outputFileUrl.path, contents: nil)
+    guard FileManager.default.createFile(atPath: outputFileUrl.path, contents: nil) else {
+      throw ReductionError("Failed to create file at \(outputFileUrl)")
+    }
     let fileHandle = try FileHandle(forWritingTo: outputFileUrl)
 
     let toolchains = try await toolchainRegistry.toolchains

Sources/SKTestSupport/SkipUnless.swift

@@ -471,7 +471,10 @@ package actor SkipUnless {
         .appending(component: "swift-frontend")
       return try await withTestScratchDir { scratchDirectory in
         let input = scratchDirectory.appending(component: "Input.swift")
-        FileManager.default.createFile(atPath: input.pathString, contents: nil)
+        guard FileManager.default.createFile(atPath: input.pathString, contents: nil) else {
+          struct FailedToCrateInputFileError: Error {}
+          throw FailedToCrateInputFileError()
+        }
         // If we can't compile for wasm, this fails complaining that it can't find the stdlib for wasm.
         let process = Process(
           args: swiftFrontend.pathString,