fix: fix frontend tests failing due to expecting error codes instead of runtime exceptions

src/main/wacc/Main.scala

@@ -40,9 +40,12 @@ val cliParser = {
 
 def frontend(
     contents: String
-)(using stdout: PrintStream): IO[microWacc.Program] = {
-  IO(parser.parse(contents)).flatMap {
-    case Failure(msg) => IO.raiseError(new RuntimeException(msg))
+)(using stdout: PrintStream): IO[Either[Int, microWacc.Program]] = {
+  IO(parser.parse(contents)).map {
+    case Failure(msg) =>
+      stdout.println(msg)
+      Left(100) // Syntax error
+
     case Success(prog) =>
       given errors: mutable.Builder[Error, List[Error]] = List.newBuilder
       given errorContent: String = contents
@@ -52,13 +55,13 @@ def frontend(
 
       val typedProg = typeChecker.check(prog)
 
-    if (errors.result.isEmpty) IO.pure(typedProg)
+      if (errors.result.isEmpty) Right(typedProg)
       else {
         errors.result.foreach(printError)
-        IO.raiseError(new RuntimeException("Compilation failed with code: " + errors.result.view.map {
+        Left(errors.result.view.map {
           case _: Error.InternalError => 201
           case _                      => 200
-    }.max))
+        }.max)
       }
   }
 }
@@ -73,14 +76,18 @@ def compile(filename: String, outFile: Option[File] = None)(using
 ): IO[Int] =
   for {
     contents <- IO(os.read(os.Path(filename)))
-  typedProg <- frontend(contents)
-  _ <- IO {
+    result <- frontend(contents)
+    exitCode <- result match {
+      case Left(code) => IO.pure(code) // Return error code
+      case Right(typedProg) =>
+        IO {
           writer.writeTo(
             backend(typedProg),
             PrintStream(outFile.getOrElse(File(filename.stripSuffix(".wacc") + ".s")))
           )
+        }.as(0) // Compilation succeeded
     }
-} yield 0
+  } yield exitCode
 
 object Main extends IOApp.Simple {
   override def run: IO[Unit] =