syn/
lifetime.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
#[cfg(feature = "parsing")]
use crate::lookahead;
use proc_macro2::{Ident, Span};
use std::cmp::Ordering;
use std::fmt::{self, Display};
use std::hash::{Hash, Hasher};

/// 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")]
pub_if_not_doc! {
    #[doc(hidden)]
    #[allow(non_snake_case)]
    pub fn Lifetime(marker: lookahead::TokenMarker) -> Lifetime {
        match marker {}
    }
}

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

    #[cfg_attr(docsrs, 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 crate::lifetime::Lifetime;
    use proc_macro2::{Punct, Spacing, TokenStream};
    use quote::{ToTokens, TokenStreamExt};

    #[cfg_attr(docsrs, 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);
        }
    }
}