Use TryFrom in interpreter API instead of TryInto

[akiross]

Using the interpreter API, I noticed that Value implements TryInto instead of TryFrom: this has a few drawbacks and the doc suggests to avoid direct implementation. For example while it's possible to do

let v = Value::from(123i32);
let can_do: i32 = v.try_into().expect("Not a i32");

but it is not possible to do

let v = Value::from(123i32);
let cant_do: i32 = i32::try_from(v).expect("Not a i32");

Implementing TryFrom<Value> for $ty will provide a blanket implementation for TryInto<$ty> for Value, while the inverse is not true. This would also allow to implement functions with generic types that can be obtained from a value, like where T: TryFrom<Value> - while AFAICT this is not possible with the current implementation, without using workarounds.

I forked slint with the intent to open a PR, but I stopped before actually opening it because I'm not sure if this choice was intentional or not (I see no reason why to avoid implementing TryFrom instead of TryInto, but you might have some).

Would a PR be welcome to fix this?

[ogoffart]

Yes, please open a PR. I don't think this was intentional

[ogoffart]

And, in fact, since the conversion cannot fail, i believe even implementing From would be working

Edit: ignore that. From is already implemented. And it's for the conversion to the inner type, and yes, then TryFrom can be used.