Fix position used in variance error message

Author: smarter

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

@@ -112,10 +112,10 @@ class VarianceChecker()(implicit ctx: Context) {
       case Some(VarianceError(tvar, required)) =>
         def msg = i"${varianceString(tvar.flags)} $tvar occurs in ${varianceString(required)} position in type ${sym.info} of $sym"
         if (ctx.scala2Mode && sym.owner.isConstructor) {
-          ctx.migrationWarning(s"According to new variance rules, this is no longer accepted; need to annotate with @uncheckedVariance:\n$msg", sym.pos)
+          ctx.migrationWarning(s"According to new variance rules, this is no longer accepted; need to annotate with @uncheckedVariance:\n$msg", pos)
           patch(Position(pos.end), " @scala.annotation.unchecked.uncheckedVariance") // TODO use an import or shorten if possible
         }
-        else ctx.error(msg, sym.pos)
+        else ctx.error(msg, pos)
       case None =>
     }