fn foo() -> u64 { [1_u64].iter().sum() + 1 } fn main() {}

error[E0283]: type annotations needed --> ...\test.rs:2:20 | 2 | [1_u64].iter().sum() + 1 | ^^^ cannot infer type for type parameter `S` declared on the associated function `sum` | = note: cannot satisfy `_: Sum<&u64>` note: required by a bound in `std::iter::Iterator::sum` help: consider specifying the type argument in the method call | 2 | [1_u64].iter().sum::<S>() + 1 | +++++ help: consider specifying the type argument in the function call | 2 | [1_u64].iter().sum::<S>() + 1 | +++++ error: aborting due to previous error For more information about this error, try `rustc --explain E0283`.