Fallible try_map on Option

(This is a re-post of https://github.com/rust-lang/rust/issues/38282, just in the correct place.) Using Option::map together with the ? operator is a pain. If you are mapping over an optional type, you can't use ? inside the closure to signal error. This means that it's often impractical to map functions that return Results over optional types. Here's a way to alleviate that:

item.explanation = item.explanation
    .and_then(|s| sanitize_links(&s).ok() ); // FIXME silently ignores errors

...but as noted in the comment, in the cases where the error matters, this is bad, and needs to be refactored into a match statement.

It would help the ergonomics, if Option<T> had a method – let's call it fallible_map EDIT: a better name was suggested by @killercup: try_map – like this:

try_map(self, FnOnce(T) → Result<U, E>) → Result<Option<U>, E>

What it would do, it would map the function over T, but wrap an Ok result into Option and return that Option wrapped into a Result. This would allow mapping fallible functions over Options:

item.explanation = item.explanation
    .try_map(|s| sanitize_links(&s))?;

...which, combined with ?, allows neat, fluid APIs while handling errors properly.

Does adding this kind of an API to Option need an RFC?

A simple implementation was demonstrated by @killercup here. As he mentioned, it could live in a 3rd party crate, but as a simple helper method that is in many ways similar to the already-existing Option::map, Option::and_then and others, helping with massaging the types in the right shape, I could easily imagine it being part of the standard API.

Note that alternative to this would be a method over Option<Result<T, E>> that would "flip" the types to Result<Option<T>, E>.

Start by comparing the proposed behavior with the existing Option::map and Option::and_then APIs, then review the linked prior issue and playground implementation. Determine whether try_map belongs in the standard API and whether an RFC is required; done would be a resolved API-design decision or an accepted RFC.