This error indicates that the compiler cannot guarantee a matching pattern for one or more possible inputs to a match expression. Guaranteed matches are required in order to assign values to match expressions, or alternatively, determine the flow of execution.
Erroneous code example:
enum Terminator {
HastaLaVistaBaby,
TalkToMyHand,
}
let x = Terminator::HastaLaVistaBaby;
match x { // error: non-exhaustive patterns: `HastaLaVistaBaby` not covered
Terminator::TalkToMyHand => {}
}
RunIf you encounter this error you must alter your patterns so that every possible
value of the input type is matched. For types with a small number of variants
(like enums) you should probably cover all cases explicitly. Alternatively, the
underscore _
wildcard pattern can be added after all other patterns to match
“anything else”. Example:
enum Terminator {
HastaLaVistaBaby,
TalkToMyHand,
}
let x = Terminator::HastaLaVistaBaby;
match x {
Terminator::TalkToMyHand => {}
Terminator::HastaLaVistaBaby => {}
}
// or:
match x {
Terminator::TalkToMyHand => {}
_ => {}
}
Run