XO0201: Result value is never used

error · reported by the checker

Handling errors is mandatory. A Result value that is not propagated with ?, matched, passed, returned, or stored is an error, and so is a Result bound to a name that is never used, whatever the name (including _x). This covers expression statements, defer, loop bodies, if without else, and the tail of a unit function or closure. The diagnostic offers ? as a fix. To discard on purpose, write .ignore_err("reason"). See core 2.6.

Example

enum E { A }

fn g() -> Int ! E { 1 }

fn f() {
  g()
}

Fix

enum E { A }

fn g() -> Int ! E { 1 }

fn f() ! E {
  g()?
}

Run xo explain XO0201 for this text in a terminal, or see section 10.6 of the specification.

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XO0201: Result value is never used

Example

Fix