Method `as_ref` not suggested when it should

[KillTheMule]

As per https://www.reddit.com/r/rust/comments/9pb3ah/what_cool_stuff_have_you_learned_about_rust/e80zqpc/, I'm reporting a case where the method as_ref is not suggested by the compiler to use to convert an &Option<T> to an Option<&T>. Here's a playground link, the non-working code is

pub struct Keyword {}

pub struct ParsedLine<'a> {
  pub keyword: Option<&'a Keyword>,
}

impl<'a> From<&'a Option<Keyword>> for ParsedLine<'a>
{
  fn from(k: &'a Option<Keyword>) -> ParsedLine<'a>
  {
      ParsedLine{keyword: k}
  }
}

error[E0308]: mismatched types
  --> src/main.rs:13:27
   |
13 |       ParsedLine{keyword: k}
   |                           ^ expected enum `std::option::Option`, found reference
   |
   = note: expected type `std::option::Option<&Keyword>`
              found type `&'a std::option::Option<Keyword>`

The playground is using stable, I'm seeing this behavior on rustc 1.31.0-nightly (de3d640f5 2018-10-01) as well locally. If I should provide more information, let me know :)

[estebank]

For both Result (if appropriate) and Option it should suggest using as_ref():

error[E0308]: mismatched types
  --> src/main.rs:13:27
   |
13 |       ParsedLine{keyword: k}
   |                           ^
   |                           |
   |                           expected enum `std::option::Option`, found reference
   |                           help: use `as_ref` here: `k.as_ref()`
   |
   = note: expected type `std::option::Option<&Keyword>`
              found type `&'a std::option::Option<Keyword>`