Bad error message when using try operator in a closure

[eira-fransham]

Minimal reproduction:

|| {
    Err(())?;
    Ok(())
}

Leads to an error message like:

error[E0282]: type annotations needed
 --> src/main.rs:3:9
  |
3 |         Err(())?;
  |         --------
  |         |
  |         cannot infer type for `_`
  |         in this macro invocation

error: aborting due to previous error

Because ? uses Into and it's ambiguous which type you're converting this error into. Even as a relatively-veteran Rust programmer it still took me some time and playing around before I worked out what was causing this error, I can't imagine how it must be for a new recruit. I think the ideal solution would be to have it default to Into<Self> as long as the error types of all of the expressions ? is used on match, but that would require an RFC and at the bare minimum a more explicit error message could be written for this case.

[estebank]

Current output:

error[E0282]: type annotations needed for `[closure@src/main.rs:3:13: 6:6]`
 --> src/main.rs:4:9
  |
3 |     let x = || {
  |         - consider giving `x` the explicit type `[closure@src/main.rs:3:13: 6:6]`, with the type parameters specified
4 |         Err(())?;
  |         ^^^^^^^^ cannot infer type