1 files changed, 58 insertions, 0 deletions
diff --git a/main/moduledefs/src/mill/moduledefs/AutoOverridePlugin.scala b/main/moduledefs/src/mill/moduledefs/AutoOverridePlugin.scala
new file mode 100644
index 00000000..5b33abbe
--- /dev/null
+++ b/main/moduledefs/src/mill/moduledefs/AutoOverridePlugin.scala
@@ -0,0 +1,58 @@
+package mill.moduledefs
+
+import scala.reflect.internal.Flags
+import scala.tools.nsc.io.VirtualFile
+import scala.tools.nsc.util.BatchSourceFile
+import scala.tools.nsc.{Global, Phase}
+import scala.tools.nsc.plugins.{Plugin, PluginComponent}
+
+class AutoOverridePlugin(val global: Global) extends Plugin {
+  import global._
+  override def init(options: List[String],  error: String => Unit): Boolean = true
+
+  val name = "auto-override-plugin"
+  val description = "automatically inserts `override` keywords for you"
+  val components = List[PluginComponent](
+    new PluginComponent {
+
+      val global = AutoOverridePlugin.this.global
+      import global._
+
+      override val runsAfter = List("typer")
+      override val runsBefore = List("patmat")
+
+      val phaseName = "auto-override"
+
+      override def newPhase(prev: Phase) = new GlobalPhase(prev) {
+
+        def name: String = phaseName
+
+        def isCacher(owner: Symbol) = {
+          val baseClasses =
+            if (owner.isClass) Some(owner.asClass.baseClasses)
+            else if (owner.isModule) Some(owner.asModule.baseClasses)
+            else None
+          baseClasses.exists(_.exists(_.fullName == "mill.moduledefs.Cacher"))
+        }
+
+        def apply(unit: global.CompilationUnit): Unit = {
+          object AutoOverrider extends global.Transformer {
+            override def transform(tree: global.Tree) = tree match{
+              case d: DefDef
+                if d.symbol.overrideChain.count(!_.isAbstract) > 1
+                && !d.mods.isOverride
+                && isCacher(d.symbol.owner) =>
+
+                  d.symbol.flags = d.symbol.flags | Flags.OVERRIDE
+                  copyDefDef(d)(mods = d.mods | Flags.OVERRIDE)
+              case _ => super.transform(tree)
+
+            }
+          }
+
+          unit.body = AutoOverrider.transform(unit.body)
+        }
+      }
+    }
+  )
+}
+\ No newline at end of file