What is the reason behind inability to use several trait bounds for a trait object?

Rust Users Forum2026-11-15 08:480 views

It works

trait CoffieSort { fn drink(&self); } trait ProgrammingLanguage { fn code(&self); } trait JavaJar { fn get(&self) -> impl CoffieSort + ProgrammingLanguage; }

but if I wanted to use a dynamic trait

trait JavaJar { fn get(&self) -> &dyn CoffieSort + ProgrammingLanguage; }

I would face

I wonder, what were the technical reasons of this limitation? At first glance, nothing prevents compiler from checking it a compile time, so I believe it has something to do with a trait object structure, but from what I see it only has a vtable pointer, and doesn't care about traits.

4 posts - 3 participants

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Source：https://users.rust-lang.org/t/what-is-the-reason-behind-inability-to-use-several-trait-bounds-for-a-trait-object/143682

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