Passing None for data results in compile error

[jwilm]

request is declared as

pub fn request<S, D>(method: Method, url: &str, data: Option<S>) -> Result<Option<D>>

The compiler errors when data is None because now the type S is undefined.

error: unable to infer enough type information about `_`; type annotations or generic parameter binding required

There is a failing test here which demonstrates the desired behavior.

[bluss]

The type S matters, so it must be inferred somehow. In the future, with type param defaults properly turned on, you can set a default. For now you must choose a type, for example by hinting on the none: None::<Xyz>.

[jwilm]

What do you mean here?

with type param defaults properly turned on

Is that an upcoming language feature?

[bluss]

Yep, see rust-lang/rust/issues/27336

It's an existing unstable feature, not stable yet.

[jwilm]

Thanks for the link.

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