Move `contain` outside of mako.

[emilio]

See #19015.

[emilio]

Tentatively assigning it to @stevel98 :)

[stevel98]

Hi,
I'm still new to rust, and I'm puzzled over the purpose of the computed_value module under the contains longhand in box.mako.rs.

pub mod computed_value {
    pub type T = super::SpecifiedValue;
}

I only see it used in:

#[inline]
pub fn get_initial_value() -> computed_value::T {
    computed_value::T::empty()
}

But wouldn't this be the same as:

#[inline]
pub fn get_initial_value() -> computed_value::T {
    Self::empty()
}

[CYBAI]

@stevel98

This block means you can just implement the Contain type inside specified module; then, due to same for both specified and computed, you can just export (pub use) the specified type in computed module. You can check this PR. I think they're not same but similar.

pub mod computed_value {
    pub type T = super::SpecifiedValue;
}

For this block, yeah, you can use Self::empty().

#[inline]
pub fn get_initial_value() -> computed_value::T {
    computed_value::T::empty()
}

Another note:

For this case, I didn't try but maybe you don't need this get_initial_value function? I think you can just use empty for initial_value?

cc @emilio
If I'm wrong, please correct me :P

[emilio]

Yes, but in this case, since the types are the same, it's completely redundant to use computed_value::T instead of Self. This is the kind of stuff we're trying to remove :)

[stevel98]

Thanks! I'll try to remove it then.