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Comment by jgilias | Hacker News Reader

Nobody forces you to rely on type inference. It’s perfectly valid Rust where you type everything if you so wish. This might actually be a good way to learn the ins and outs of the type system.

EDIT: Also, what do you mean by type ‘coercion’? As far as I know the types in Rust are never silently coerced to anything. They just are what they are.

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They mean inference. Generics get resolved to different types (and lifetimes) depending on surrounding code.

wow, I never contemplated before whether that kind of language design could be evil, but you make me think it might be. Maybe not in the ordinary course of sensible use, but in some horrible "I didn't think of that". Then I feel a bit hypocritical because I'm sure I've relied on a hundred more problematic abstractions without worrying about it.

Far from evil, it's amazingly useful, and is why things like `let x: Vec<_> = foo.collect();` work (the return type of the `collect` method is generic). Rust stops type inference at function boundaries, so the precise type of something is never far away if you need it.

I concur. Rust does it very sensible and elegantly. I will note that the other thing rust does is let you under specify the lifetimes of a function signature but when compile errors happen they tell you what they ended up inferring and you can always correct it when you need something slightly different. The two features are critical in making Rust code easy to read and write as the types and lifetimes can get tedious and most of you have to specify it literally everywhere.

> As far as I know the types in Rust are never silently coerced to anything.

There are some specific coercion sites and kinds: https://doc.rust-lang.org/reference/type-coercions.html

True, although coercion in Rust is quite limited (it doesn't even coerce smaller ints into larger ones), and the coercions that exist are pretty harmless IMO (like letting you call a function that accepts a `&foo` if all you have is a `&mut foo`). I suspect they're referring to something else, as I've never seen coercion highlighted as a pain point before.

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