error.rs

use core::fmt;

#[derive(Debug)]
pub struct ParseError(ParseErrorKind);

#[derive(Debug)]
enum ParseErrorKind {
    EmptyFlag,
    InvalidNamedFlag {
        #[cfg(not(feature = "std"))]
        got: (),
        #[cfg(feature = "std")]
        got: String,
    },
    InvalidHexFlag {
        #[cfg(not(feature = "std"))]
        got: (),
        #[cfg(feature = "std")]
        got: String,
    },
}

impl ParseError {
    pub fn invalid_hex_flag(flag: impl fmt::Display) -> Self {
        let _flag = flag;

        let got = {
            #[cfg(feature = "std")]
            {
                _flag.to_string()
            }
        };

        ParseError(ParseErrorKind::InvalidHexFlag { got })
    }

    pub fn invalid_named_flag(flag: impl fmt::Display) -> Self {
        let _flag = flag;

        let got = {
            #[cfg(feature = "std")]
            {
                _flag.to_string()
            }
        };

        ParseError(ParseErrorKind::InvalidNamedFlag { got })
    }

    pub fn empty_flag() -> Self {
        ParseError(ParseErrorKind::EmptyFlag)
    }
}

impl fmt::Display for ParseError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self.0 {
            ParseErrorKind::InvalidNamedFlag { got } => {
                let _got = got;

                write!(f, "unrecognized named flag")?;

                #[cfg(feature = "std")]
                {
                    write!(f, " `{}`", _got)?;
                }
            }
            ParseErrorKind::InvalidHexFlag { got } => {
                let _got = got;

                write!(f, "invalid hex flag")?;

                #[cfg(feature = "std")]
                {
                    write!(f, " `{}`", _got)?;
                }
            }
            ParseErrorKind::EmptyFlag => {
                write!(f, "encountered empty flag")?;
            }
        }

        Ok(())
    }
}

#[cfg(feature = "std")]
impl std::error::Error for ParseError {}