Voldemort Type Construction Error

[Nordlöw via Digitalmars-d-learn]

I've made progress at the helper findingSplitter at

https://github.com/nordlow/justd/blob/master/substitution.d#L122

I need this for implementing a new Phobos lazy `substitute()` (or 
replace).

I've done most logic (AFAICT in my head) but I can't make the 
call to Result() work as it fails as

substitution.d(187,18): Error: struct 
substitution.findingSplitter!("a == b", string, string, string, 
string).findingSplitter.Result cannot deduce function from 
argument types !()(string, string, string, string), candidates 
are:
substitution.d(126,12):        substitution.findingSplitter!("a 
== b", string, string, string, string).findingSplitter.Result()
substitution.d(194,32): Error: template instance 
substitution.findingSplitter!("a == b", string, string, string, 
string) error instantiating
substitution.d(196,12): Error: undefined identifier 'equal', did 
you mean alias 'Unqual'?
/home/per/Work/justd/traits_ex.d(64,13): Warning: statement is 
not reachable

What have I missed?