Macro func_name 

macro_rules! func_name {
    () => { ... };
    (<$param:ident> $ty:ty => $name:literal, $($rest:tt)*) => { ... };
    ($ty:ty => $name:literal, $($rest:tt)*) => { ... };
}

Declares the canonical FuncName of hand-written function structs. Functions generated by #[sqlfunc] get theirs from that macro instead. Structs generic over an expression type declare a leading <E>.