Fix experimental annotation detection

Author: nicolasstucki

compiler/src/dotty/tools/dotc/typer/RefChecks.scala

@@ -978,15 +978,9 @@ object RefChecks {
     then
       Feature.checkExperimentalDef(sym, pos)
 
-  private def checkExperimentalTypes(tpe: Type, pos: SrcPos)(using Context): Unit =
-    val checker = new TypeTraverser:
-      def traverse(tp: Type): Unit =
-        if tp.typeSymbol.isExperimental then
-          Feature.checkExperimentalDef(tp.typeSymbol, pos)
-        else
-          traverseChildren(tp)
-    if !pos.span.isSynthetic then // avoid double errors
-      checker.traverse(tpe)
+  private def checkExperimentalAnnots(sym: Symbol)(using Context): Unit =
+    for annot <- sym.annotations if annot.symbol.isExperimental do
+      Feature.checkExperimentalDef(annot.symbol, annot.tree)
 
   /** If @migration is present (indicating that the symbol has changed semantics between versions),
    *  emit a warning.
@@ -1225,6 +1219,7 @@ class RefChecks extends MiniPhase { thisPhase =>
   override def transformValDef(tree: ValDef)(using Context): ValDef = {
     checkNoPrivateOverrides(tree)
     checkDeprecatedOvers(tree)
+    checkExperimentalAnnots(tree.symbol)
     val sym = tree.symbol
     if (sym.exists && sym.owner.isTerm) {
       tree.rhs match {
@@ -1245,6 +1240,7 @@ class RefChecks extends MiniPhase { thisPhase =>
   override def transformDefDef(tree: DefDef)(using Context): DefDef = {
     checkNoPrivateOverrides(tree)
     checkDeprecatedOvers(tree)
+    checkExperimentalAnnots(tree.symbol)
     checkImplicitNotFoundAnnotation.defDef(tree.symbol.denot)
     tree
   }
@@ -1258,6 +1254,7 @@ class RefChecks extends MiniPhase { thisPhase =>
     checkAllOverrides(cls)
     checkImplicitNotFoundAnnotation.template(cls.classDenot)
     checkExperimentalInheritance(cls)
+    checkExperimentalAnnots(cls)
     tree
   }
   catch {
@@ -1307,6 +1304,12 @@ class RefChecks extends MiniPhase { thisPhase =>
     checkUndesiredProperties(tree.symbol, tree.srcPos)
     tree
   }
+
+  override def transformTypeDef(tree: TypeDef)(using Context): TypeDef = {
+    checkUndesiredProperties(tree.symbol, tree.srcPos)
+    checkExperimentalAnnots(tree.symbol)
+    tree
+  }
 }
 
 /* todo: rewrite and re-enable

tests/neg-custom-args/no-experimental/experimentalAnnot.scala

@@ -0,0 +1,7 @@
+import scala.annotation.experimental
+
+@experimental // error
+class myExperimentalAnnot extends scala.annotation.Annotation
+
+@myExperimentalAnnot // error
+def test: Unit = ()

tests/neg-custom-args/no-experimental/experimentalEnum.scala

@@ -1,9 +1,10 @@
+// nopos-error // nopos-error // nopos-error // FIXME redundant due to enum
 import scala.annotation.experimental
 
-@experimental // FIXME ERROR
-enum E: // error
+@experimental // error
+enum E:
   case A
-  case B // error
+  case B
 
 def test: Unit =
   E.A // error

tests/neg-custom-args/no-experimental/experimentalExperimental.scala

@@ -1,2 +1,4 @@
+import scala.annotation.experimental
+
 class MyExperimentalAnnot // error
-extends scala.annotation.experimental // error
+  extends experimental // error

tests/neg-custom-args/no-experimental/experimentalnline.scala renamed to tests/neg-custom-args/no-experimental/experimentalInline.scala

@@ -1,6 +1,6 @@
 import scala.annotation.experimental
 
-@experimental // FIXME ERROR
+@experimental
 inline def g() = ()
 
 def test: Unit =

tests/neg-custom-args/no-experimental/experimentalOverride.scala

@@ -1,22 +1,22 @@
 import scala.annotation.experimental
 
-@experimental // FIXME ERROR
+@experimental // error
 class A:
   def f() = 1
 
-@experimental // FIXME ERROR
+@experimental // error
 class B extends A:
   override def f() = 2
 
 class C:
-  @experimental // FIXME ERROR
+  @experimental // error
   def f() = 1
 
 class D extends C:
   override def f() = 2
 
 trait A2:
-  @experimental // FIXME ERROR
+  @experimental // error
   def f(): Int
 
 trait B2:

tests/neg-custom-args/no-experimental/experimentalSam.scala

@@ -1,6 +1,6 @@
 import scala.annotation.experimental
 
-@experimental // FIXME ERROR
+@experimental // error
 trait ExpSAM {
   def foo(x: Int): Int
 }

tests/neg-custom-args/no-experimental/experimentalTerms.scala

@@ -1,12 +1,12 @@
 import scala.annotation.experimental
 
-@experimental // FIXME ERROR
+@experimental // error
 val x = ()
 
-@experimental // FIXME ERROR
+@experimental // error
 def f() = ()
 
-@experimental // FIXME ERROR
+@experimental // error
 object X:
   def fx() = 1
 

tests/neg-custom-args/no-experimental/experimentalType.scala

@@ -1,19 +1,19 @@
 import scala.annotation.experimental
 
-@experimental // FIXME ERROR
+@experimental // error
 class A
 
-@experimental // FIXME ERROR
+@experimental // error
 class B extends A
 
-@experimental // FIXME ERROR
-type X
+@experimental
+type X // error
 
-@experimental // FIXME ERROR
-type Y = Int
+@experimental
+type Y = Int // error
 
-@experimental // FIXME ERROR
-opaque type Z = Int
+@experimental
+opaque type Z = Int // error
 
 def test(
   p1: A, // error

tests/neg-custom-args/no-experimental/experimentalUnapply.scala

@@ -1,13 +1,13 @@
 import scala.annotation.experimental
 
-@experimental // FIXME ERROR
+@experimental // error
 class A
 
 object Extractor1:
   def unapply(s: Any): Option[A] = ??? // FIXME ERROR
 
 object Extractor2:
-  @experimental // FIXME ERROR
+  @experimental // error
   def unapply(s: Any): Option[Int] = ???
 
 def test: Unit =