diff -r 9efdebe24c65 -r 0ffcad1f6130 src/Pure/Tools/scala_project.scala
--- a/src/Pure/Tools/scala_project.scala	Mon Mar 01 20:12:09 2021 +0100
+++ b/src/Pure/Tools/scala_project.scala	Mon Mar 01 22:22:12 2021 +0100
@@ -104,7 +104,7 @@
 
   /* scala project */
 
-  def scala_project(project_dir: Path, symlinks: Boolean = false)
+  def scala_project(project_dir: Path, symlinks: Boolean = false): Unit =
   {
     if (symlinks && Platform.is_windows)
       error("Cannot create symlinks on Windows")