False positive warning for extension method (taking Seq) shadowing (varargs) #24198
Description
Compiler version
3.7.3, 3.8.0-RC1-bin-20251017-96aff06-NIGHTLY
Minimized code
object test {
class A {
def m(p: String*): Unit = println("member")
}
extension (a: A) def m(p: Seq[String]): Unit = println("extension")
def main(args: Array[String]): Unit = {
(new A).m(Seq[String]())
}
}Output
$ scala-cli -S 3.nightly extension.scala
Compiling project (Scala 3.8.0-RC1-bin-20251017-96aff06-NIGHTLY, JVM (21))
[warn] ./extension.scala:3:24
[warn] Extension method m will never be selected from type A
[warn] because A already has a member with the same name and compatible parameter types.
[warn] extension (a: A) def m(p: Seq[String]): Unit = println("extension")
[warn] ^
Compiled project (Scala 3.8.0-RC1-bin-20251017-96aff06-NIGHTLY, JVM (21))
extension
Expectation
The compiler should not produce a warning. The warning is a false positive because the extension method is selected and called.