Find the error in the following ML code:

fun charListToStringList $[]=[]$

$|$ charListToStringList $($#$""$::xs$)=""$::charListToStringList$($xs$)$

$|$ charListToStringList $($#$"$i$"$::#$"$n$"$::#$"$t$"$::xs$)=$ "int"::charListToStringList$($xs$)$

$|$ charListToStringList $($x::xs$)=$ Char.toString x :: charListToStringList$($xs$)$;

When compiled it throughs the following error:

stdIn:$223\mathrm{.}27-223\mathrm{.}40$ Error: non$-$constructor applied to argument in pattern