E0032

Warning name: unused_default_value

Default value of optional argument is unused. This implies at every call site of this function, the optional argument is always explicitly supplied with a value. This means the optional argument can be refactored into a labelled argument.

Erroneous example

This warning is turned off by default. Enable it with the warnings field in moon.pkg:

moon.pkg

warnings = "+unused_default_value"

pkgtype(kind: "executable")

main.mbt

///|
fn f(opt? : Int = 4) -> Int {
  ignore(opt)
  0
}

///|
fn main {
  println(f(opt=3))
  println(f(opt=3))
}

Suggestion

Turn the optional argument into a labelled argument:

///|
fn f(opt~ : Int) -> Int {
  ignore(opt)
  0
}

///|
fn main {
  println(f(opt=3))
  println(f(opt=3))
}