nameless 0.15.2

Portable everything-is-a-URL
Documentation 
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use crate::MediaType;
use clap::{AmbientAuthority, TryFromOsArg};
use std::error::Error;
use std::ffi::{OsStr, OsString};
use std::fmt;
use std::marker::PhantomData;

#[doc(hidden)]
#[derive(Debug)]
pub struct Never {}

impl Error for Never {}

impl fmt::Display for Never {
    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
        panic!()
    }
}

#[doc(hidden)]
pub trait FromLazyOutput {
    type Err;

    fn from_lazy_output(
        name: OsString,
        media_type: MediaType,
        ambient_authority: AmbientAuthority,
    ) -> Result<Self, Self::Err>
    where
        Self: Sized;
}

/// A placeholder for an output stream which is created lazily. It is created
/// when `materialize` is called.
pub struct LazyOutput<T: FromLazyOutput> {
    name: OsString,
    ambient_authority: AmbientAuthority,
    _phantom: PhantomData<T>,
}

impl<T: FromLazyOutput> LazyOutput<T> {
    /// Consume `self` and materialize an output stream.
    #[inline]
    pub fn materialize(self, media_type: MediaType) -> Result<T, T::Err> {
        T::from_lazy_output(self.name, media_type, self.ambient_authority)
    }
}

impl<T: FromLazyOutput> TryFromOsArg for LazyOutput<T> {
    type Error = Never;

    #[inline]
    fn try_from_os_str_arg(os: &OsStr, ambient_authority: AmbientAuthority) -> Result<Self, Never> {
        Ok(Self {
            name: os.to_owned(),
            ambient_authority,
            _phantom: PhantomData::default(),
        })
    }
}