You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: errors.rs
    path of file: ./repos/fluent-rs/fluent-bundle/src/resolver
    
    the code of the file until where you have to start completion: use fluent_syntax::ast::InlineExpression;
use std::error::Error;

/// Maps an [`InlineExpression`] into the kind of reference, with owned strings
/// that identify the expression. This makes it so that the [`InlineExpression`] can
/// be used to generate an error string.
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum ReferenceKind {
    Function {
        id: String,
    },
    Message {
        id: String,
        attribute: Option<String>,
    },
    T
    
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Reference(exp) => match exp {
                ReferenceKind::Function { id } => write!(f, "Unknown function: {}()", id),
                ReferenceKind::Message {
                    id,
                    attribute: None,
                } => write!(f, "Unknown message: {}", id),
                ReferenceKind::Message {
                    id,
                    attribute: Some(attribute),
                } => write!(f, "Unknown attribute: {}.{}", id, attribute),
                ReferenceKind::Term {
                    id,
                    attribute: None,
                } => write!(f, "Unknown term: -{}", id),
                ReferenceKind::Term {
                    id,
                    attribute: Some(attribute),
                } => write!(f, "Unknown attribute: -{}.{}", id, attribute),
                ReferenceKind::Variable { id } => write!(f, "Unknown variable: ${}", id),
            },
            Self::NoValue(id) => write!(f, "No value: {}", id),
            Self::MissingDefault => f.write_str("No default"),
            Self::Cyclic => f.write_str("Cyclical dependency detected"),
            Self::TooManyPlaceables => f.write_str("Too many placeables"),
        }
    }