This isn't about type system per se but about preferred style of syntax. Original example that caused my hatred looked like this: `let i : uint = from_str("42")`. Fortunately this has been deprecated in favor of `parse` but same principle applies - Rust authors encourage you to use declaration for type deduction instead of expression.

Same thing can be rewritten as `let i = from_str::<uint>("42")` without compromising any type strictness Rust is proud of. In this form RHS expression has clear unambiguous type and can be copied anywhere. But this is discouraged form. More than that, when I was pointing out ugly template syntax, I got some comments that it is OK exactly because you are always supposed to put type on LHS. This is purely matter of style decisions and it sucks hard.