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This post is auto-generated from RSS feed The Rust Programming Language Forum - Latest topics. Source: "lifetime may not live long enough" error that occurs only with "dyn Trait"

Hello.

This code compiles:

fn test<'a>(s: Option<&'a mut Box<u32>>) {
    consume(s.map(|x| x.as_mut()));
}

fn consume<'a>(s: Option<&'a mut u32>) {}

But this code doesn’t:

trait Test {}

fn test<'a>(s: Option<&'a mut Box<dyn Test>>) {
    // error: lifetime may not live long enough
    //     |
    // 167 | fn test<'a>(s: Option<&'a mut Box<dyn Test>>) {
    //     |         -- lifetime `'a` defined here
    // 168 |     consume(s.map(|x| x.as_mut()));
    //     |                       ^^^^^^^^^^ returning this value requires that `'a` must outlive `'static`
    consume(s.map(|x| x.as_mut()));
}

fn consume<'a>(s: Option<&'a mut dyn Test>) {}

The only difference is the u32 was replaced with dyn Trait.

Why the code doesn’t compile? Why it matters if it is dyn Trait or u32 ?

Thanks you!

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