F# Partial Active Pattern Matching "Rule Will Never Be Matched" -

given following active pattern:

let (| hasmatch |) (x:string) =    if x.contains("0") some()   else none;;

and following pattern matching func:

let testfn x = function   | hasmatch -> printfn "%a"   | _ -> printf "nope";;

the last line's wildcard pattern says warning fs0026: rule never matched

all of examples see seem infer partial active patterns must return some('a) match, , ones return none captured wildcard. error seems differently.

what missing?

i think should add none case active pattern declaration follows:

let (| hasmatch | _ |) (x:string) =    if x.contains("0") some()   else none;;

in orignal example, compiler infers want return option type. when run printf in example, see print some null when there match.

also, bad return some(), should return some(x) or similar

Sharma