I definitely agree, this is a pain point in Rust today, and it's something the core team would like to address. You might glance at the thread here for some of

I definitely agree, this is a pain point in Rust today, and it's something the core team would like to address. You might glance at the thread here for some of the tradeoffs: https://internals.rust-lang.org/t/implicit-widening-polymorphic-indexing-and-similar-ideas/1141 https://internals.rust-lang.org/t/implicit-widening-polymorp... If we can reach consensus on a design, such a feature can be easily implemented. I'd love to see an RFC on the topic (https://github.com/rust-lang/rfcs https://github.com/rust-lang/rfcs)!