Reports

I only see two options here to address this issue, even tho I would argue that none of them is ideal:

the first one by having :

impl Displayable for ArticleView {
    type SomeState = MyMutableState<'static>;

    fn show(&self, data: &mut MyMutableState<'_>) -> String {
        format!("👋 {}, {}", data.third.title, data.buffer.len())
    }
}

This fixes the error at this level, but it makes MyMutableState only working with a &'static str for ThirdPartyState.

The second one, as first suggested by @GiM in his comment, required you to have a lifetime for ArticleView :

Comment of @GiM :

@ChayimFriedman yeah adding lifetime (and phantom data) seems to work, although that doesn't seem like a great solution :/ play.rust-lang.org/?gist=66e4d23b7439ce60243201eb3509a953

So the result will be :

use std::marker::PhantomData;
struct ArticleView<'a> {
    // Note that the version of @DiM use `phantom: PhantomData<&'a u32>` which has no difference except personal preferences
    _phantom: PhantomData<&'a ()>,
}

impl<'a> Displayable for ArticleView<'a> {
    type SomeState = MyMutableState<'a>;

    fn show(&self, data: &mut MyMutableState<'_>) -> String {
        format!("👋 {}, {}", data.third.title, data.buffer.len())
    }
}

This unfortunately changes the way ArticleView is constructed (ArticleView { _phantom: PhantomData } instead of ArticleView)

Otherwise, I actually don't thinks there is a way to constrains a lifetime to this impl without being able to modify the trait you want to implements

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