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    use proc_macro2::{Ident, Span};
    use std::cmp::Ordering;
    use std::fmt::{self, Display};
    use std::hash::{Hash, Hasher};

    #[cfg(feature = "parsing")]
    use crate::lookahead;

    /// A Rust lifetime: `'a`.
    ///
    /// Lifetime names must conform to the following rules:
    ///
    /// - Must start with an apostrophe.
    /// - Must not consist of just an apostrophe: `'`.
    /// - Character after the apostrophe must be `_` or a Unicode code point with
    ///   the XID_Start property.
    /// - All following characters must be Unicode code points with the XID_Continue
    ///   property.
    pub struct Lifetime {
        pub apostrophe: Span,
        pub ident: Ident,
    }

    impl Lifetime {
        /// # Panics
        ///
        /// Panics if the lifetime does not conform to the bulleted rules above.
        ///
        /// # Invocation
        ///
        /// ```
        /// # use proc_macro2::Span;
        /// # use syn::Lifetime;
        /// #
        /// # fn f() -> Lifetime {
        /// Lifetime::new("'a", Span::call_site())
        /// # }
        /// ```
        pub fn new(symbol: &str, span: Span) -> Self {
            if !symbol.starts_with('\'') {
                panic!(
                    "lifetime name must start with apostrophe as in \"'a\", got {:?}",
                    symbol
                );
            }

            if symbol == "'" {
                panic!("lifetime name must not be empty");
            }

            if !crate::ident::xid_ok(&symbol[1..]) {
                panic!("{:?} is not a valid lifetime name", symbol);
            }

            Lifetime {
                apostrophe: span,
                ident: Ident::new(&symbol[1..], span),
            }
        }

        pub fn span(&self) -> Span {
            self.apostrophe
                .join(self.ident.span())
                .unwrap_or(self.apostrophe)
        }

        pub fn set_span(&mut self, span: Span) {
            self.apostrophe = span;
            self.ident.set_span(span);
        }
    }

    impl Display for Lifetime {
        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            "'".fmt(formatter)?;
            self.ident.fmt(formatter)
        }
    }

    impl Clone for Lifetime {
        fn clone(&self) -> Self {
            Lifetime {
                apostrophe: self.apostrophe,
                ident: self.ident.clone(),
            }
        }
    }

    impl PartialEq for Lifetime {
        fn eq(&self, other: &Lifetime) -> bool {
            self.ident.eq(&other.ident)
        }
    }

    impl Eq for Lifetime {}

    impl PartialOrd for Lifetime {
        fn partial_cmp(&self, other: &Lifetime) -> Option<Ordering> {
            Some(self.cmp(other))
        }
    }

    impl Ord for Lifetime {
        fn cmp(&self, other: &Lifetime) -> Ordering {
            self.ident.cmp(&other.ident)
        }
    }

    impl Hash for Lifetime {
        fn hash<H: Hasher>(&self, h: &mut H) {
            self.ident.hash(h)
        }
    }

    #[cfg(feature = "parsing")]
    #[doc(hidden)]
    #[allow(non_snake_case)]
    pub fn Lifetime(marker: lookahead::TokenMarker) -> Lifetime {
        match marker {}
    }

    #[cfg(feature = "parsing")]
    pub mod parsing {
        use super::*;
        use crate::parse::{Parse, ParseStream, Result};

        #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        impl Parse for Lifetime {
            fn parse(input: ParseStream) -> Result<Self> {
                input.step(|cursor| {
                    cursor
                        .lifetime()
                        .ok_or_else(|| cursor.error("expected lifetime"))
                })
            }
        }
    }

    #[cfg(feature = "printing")]
    mod printing {
        use super::*;
        use proc_macro2::{Punct, Spacing, TokenStream};
        use quote::{ToTokens, TokenStreamExt};

        #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        impl ToTokens for Lifetime {
            fn to_tokens(&self, tokens: &mut TokenStream) {
                let mut apostrophe = Punct::new('\'', Spacing::Joint);
                apostrophe.set_span(self.apostrophe);
                tokens.append(apostrophe);
                self.ident.to_tokens(tokens);
            }
        }
    }