A bug with Identifiable: "use of undeclared lifetime name `'a`"

[golddranks]

Demonstrated by https://github.com/golddranks/diesel_bug

Setup a database with diesel_cli, set the DATABASE_URL env var and try to compile:

error[E0261]: use of undeclared lifetime name `'a`
 --> <proc-macro source code>:1:73
  |
1 | _Identifiable ! { ( table_name = sessions , struct_ty = UpdateSession < 'a > , ) , fields = [ { field_name:  id ,  column_name:  id ,  field_ty:  i32 ,  field_kind:  regular ,  } { field_name:  sess_token ,  column_name:  sess_token ,  field_ty:  & 'a [ u8 ] ,  field_kind:  regular ,  } { field_name:  proposed_token ,  column_name:  proposed_token ,  field_ty:  Option < & 'a [ u8 ] > ,  field_kind:  option ,  } { field_name:  last_ip ,  column_name:  last_ip ,  field_ty:  Vec < u8 > ,  field_kind:  regular ,  } ] , }
  |                                                                         ^^ undeclared lifetime

Caused by the Identifiable derivation with this struct in models.rs:

#[derive(Identifiable, Debug, AsChangeset)]
#[table_name="sessions"]
#[changeset_options(treat_none_as_null = "true")]
pub struct UpdateSession<'a> {
    pub id: i32,
    pub sess_token: &'a [u8],
    pub proposed_token: Option<&'a [u8]>,
    pub user_id: i32,
    pub started: DateTime<UTC>,
    pub last_seen: DateTime<UTC>,
    pub last_ip: Vec<u8>,
}