tracing: impl From<EnteredSpan> for Option<Id>

[Folyd]

Motivation

The following code compiles failed:

use tracing;

fn main() {
    
    let span = tracing::info_span!("my_span").entered();
    tracing::info!(parent: &span, "test span");
}

   Compiling playground v0.0.1 (/playground)
error[E0277]: the trait bound `Option<Id>: From<&EnteredSpan>` is not satisfied
  --> src/main.rs:6:5
   |
6  |     tracing::info!(parent: &span, "test span");
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `From<&EnteredSpan>` is not implemented for `Option<Id>`

Solution

• impl<'a> From<&'a EnteredSpan> for Option<&'a Id>.
• impl<'a> From<&'a EnteredSpan> for Option<Id>
• Add id() method into EnteredSpan.

[hawkw]

lgtm, thank you