Exit on main arg parse error

Author: som-snytt

compiler/src/dotty/tools/dotc/ast/MainProxies.scala

@@ -5,7 +5,7 @@ import core.*
 import Symbols.*, Types.*, Contexts.*, Decorators.*, util.Spans.*, Flags.*, Constants.*
 import StdNames.{nme, tpnme}
 import ast.Trees.*
-import Names.Name
+import Names.{Name, termName}
 import Comments.Comment
 import NameKinds.DefaultGetterName
 import Annotations.Annotation
@@ -94,7 +94,12 @@ object MainProxies {
       val handler = CaseDef(
         Typed(errVar, TypeTree(defn.CLP_ParseError.typeRef)),
         EmptyTree,
-        Apply(ref(defn.CLP_showError.termRef), errVar :: Nil))
+        Block(
+          List(Apply(ref(defn.CLP_showError.termRef), errVar :: Nil)),
+          Apply(Select(Select(Select(Ident(termName("java")), termName("lang")), termName("System")), termName("exit")),
+            List(Literal(Constant(1))))
+        )
+      )
       val body = Try(call, handler :: Nil, EmptyTree)
       val mainArg = ValDef(nme.args, TypeTree(defn.ArrayType.appliedTo(defn.StringType)), EmptyTree)
         .withFlags(Param)

library/src/scala/util/CommandLineParser.scala

@@ -1,23 +1,22 @@
 package scala.util
 
+import scala.util.control.ControlThrowable
+
 /** A utility object to support command line parsing for @main methods */
 object CommandLineParser {
 
   /** An exception raised for an illegal command line
-    *  @param idx  The index of the argument that's faulty (starting from 0)
-    *  @param msg  The error message
-    */
-  class ParseError(val idx: Int, val msg: String) extends Exception
+   *  @param idx  The index of the argument that's faulty (starting from 0)
+   *  @param msg  The error message
+   */
+  class ParseError(val idx: Int, val msg: String) extends ControlThrowable(msg)
 
   /** Parse command line argument `s`, which has index `n`, as a value of type `T`
    *  @throws ParseError if argument cannot be converted to type `T`.
    */
-  def parseString[T](str: String, n: Int)(using fs: FromString[T]): T = {
+  def parseString[T](str: String, n: Int)(using fs: FromString[T]): T =
     try fs.fromString(str)
-    catch {
-      case ex: IllegalArgumentException => throw ParseError(n, ex.toString)
-    }
-  }
+    catch case ex: IllegalArgumentException => throw ParseError(n, ex.toString)
 
   /** Parse `n`'th argument in `args` (counting from 0) as a value of type `T`
    *  @throws ParseError if argument does not exist or cannot be converted to type `T`.