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// Copyright 2014 Carl Lerche, Alex Crichton, Michael Gehring, Yehuda Katz
// Copyright 2015 Carl Lerche, Alex Crichton, Graham Dennis, Tamir Duberstein,
//                Robin Gloster
// Copyright 2016 Urban Hafner
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::borrow::Borrow;
use std::fmt;
use std::marker::PhantomData;

use crate::core::*;

pub struct IsNone<T> {
  marker: PhantomData<T>,
}

impl<T> fmt::Display for IsNone<T> {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    write!(f, "None")
  }
}

impl<T: fmt::Debug, B: Borrow<Option<T>>> Matcher<B> for IsNone<T> {
  fn matches(&self, actual: B) -> MatchResult {
    match actual.borrow() {
      Some(s) => Err(format!("was Some({:?})", s)),
      None => success(),
    }
  }
}

pub fn none<T>() -> IsNone<T> {
  IsNone {
    marker: PhantomData,
  }
}