ClosureExpression::new asks for all three generic types

[zecakeh]

A closure expression has to be declared like that:

gtk::ClosureExpression::new::<bool, _, _>(
    &[a_expr],
    closure!(|_: Option<Object>, a: bool| { !a }),
)

One with no parameters must be declared like that:

gtk::ClosureExpression::new::<String, &[gtk::Expression], _>(
    &[],
    closure!(|member: Option<Member>| { member.map(search_string).unwrap_or_default() }),
)

It would be great if at most we only had to annotate the ValueType, like in chain_closure. But if the closure! return type could be used for the ValueType, that would be even better.

[bilelmoussaoui]

@zecakeh I don't think there is a simple way to figure out the return type of a RustClosure, it all happens at runtime

[sdroege]

The types of the glib::Closure created by the closure! macro are unfortunately not part of the type. Doing this would require making the glib::RustClosure type generic at least. It should be doable but is a bit of work.

[zecakeh]

No problem. Just wishful thinking :)

[bilelmoussaoui]

This can be fixed now as we have bumped the minimum rust version to 1.63