I have a simple struct:

C-STRUCT: WPS_SimpleAuthentication
    { "char*" "username" }
    { "char*" "realm" } ;

Used like this:

"blah" "WPS_SimpleAuthentication" <c-object> set-WPS_SimpleAuthentication-username

results in this error:

Type check error
Object: "blah"
Object type: string
Expected type: alien