Avoid reporting extra errors on enums

Author: nicolasstucki

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

@@ -989,7 +989,7 @@ object RefChecks {
       checker.traverse(tpe)
 
   private def checkExperimentalAnnots(sym: Symbol)(using Context): Unit =
-    for annot <- sym.annotations if annot.symbol.isExperimental do
+    for annot <- sym.annotations if annot.symbol.isExperimental && annot.tree.span.exists do
       Feature.checkExperimentalDef(annot.symbol, annot.tree)
 
   /** If @migration is present (indicating that the symbol has changed semantics between versions),

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

@@ -1,4 +1,3 @@
-// nopos-error // nopos-error // nopos-error // FIXME redundant due to enum
 import scala.annotation.experimental
 
 @experimental // error