syn/
lifetime.rs

1#[cfg(feature = "parsing")]
2use crate::lookahead;
3use proc_macro2::{Ident, Span};
4use std::cmp::Ordering;
5use std::fmt::{self, Display};
6use std::hash::{Hash, Hasher};
7
8/// A Rust lifetime: `'a`.
9///
10/// Lifetime names must conform to the following rules:
11///
12/// - Must start with an apostrophe.
13/// - Must not consist of just an apostrophe: `'`.
14/// - Character after the apostrophe must be `_` or a Unicode code point with
15///   the XID_Start property.
16/// - All following characters must be Unicode code points with the XID_Continue
17///   property.
18pub struct Lifetime {
19    pub apostrophe: Span,
20    pub ident: Ident,
21}
22
23impl Lifetime {
24    /// # Panics
25    ///
26    /// Panics if the lifetime does not conform to the bulleted rules above.
27    ///
28    /// # Invocation
29    ///
30    /// ```
31    /// # use proc_macro2::Span;
32    /// # use syn::Lifetime;
33    /// #
34    /// # fn f() -> Lifetime {
35    /// Lifetime::new("'a", Span::call_site())
36    /// # }
37    /// ```
38    pub fn new(symbol: &str, span: Span) -> Self {
39        if !symbol.starts_with('\'') {
40            panic!(
41                "lifetime name must start with apostrophe as in \"'a\", got {:?}",
42                symbol
43            );
44        }
45
46        if symbol == "'" {
47            panic!("lifetime name must not be empty");
48        }
49
50        if !crate::ident::xid_ok(&symbol[1..]) {
51            panic!("{:?} is not a valid lifetime name", symbol);
52        }
53
54        Lifetime {
55            apostrophe: span,
56            ident: Ident::new(&symbol[1..], span),
57        }
58    }
59
60    pub fn span(&self) -> Span {
61        self.apostrophe
62            .join(self.ident.span())
63            .unwrap_or(self.apostrophe)
64    }
65
66    pub fn set_span(&mut self, span: Span) {
67        self.apostrophe = span;
68        self.ident.set_span(span);
69    }
70}
71
72impl Display for Lifetime {
73    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
74        "'".fmt(formatter)?;
75        self.ident.fmt(formatter)
76    }
77}
78
79impl Clone for Lifetime {
80    fn clone(&self) -> Self {
81        Lifetime {
82            apostrophe: self.apostrophe,
83            ident: self.ident.clone(),
84        }
85    }
86}
87
88impl PartialEq for Lifetime {
89    fn eq(&self, other: &Lifetime) -> bool {
90        self.ident.eq(&other.ident)
91    }
92}
93
94impl Eq for Lifetime {}
95
96impl PartialOrd for Lifetime {
97    fn partial_cmp(&self, other: &Lifetime) -> Option<Ordering> {
98        Some(self.cmp(other))
99    }
100}
101
102impl Ord for Lifetime {
103    fn cmp(&self, other: &Lifetime) -> Ordering {
104        self.ident.cmp(&other.ident)
105    }
106}
107
108impl Hash for Lifetime {
109    fn hash<H: Hasher>(&self, h: &mut H) {
110        self.ident.hash(h);
111    }
112}
113
114#[cfg(feature = "parsing")]
115pub_if_not_doc! {
116    #[doc(hidden)]
117    #[allow(non_snake_case)]
118    pub fn Lifetime(marker: lookahead::TokenMarker) -> Lifetime {
119        match marker {}
120    }
121}
122
123#[cfg(feature = "parsing")]
124pub(crate) mod parsing {
125    use crate::error::Result;
126    use crate::lifetime::Lifetime;
127    use crate::parse::{Parse, ParseStream};
128
129    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
130    impl Parse for Lifetime {
131        fn parse(input: ParseStream) -> Result<Self> {
132            input.step(|cursor| {
133                cursor
134                    .lifetime()
135                    .ok_or_else(|| cursor.error("expected lifetime"))
136            })
137        }
138    }
139}
140
141#[cfg(feature = "printing")]
142mod printing {
143    use crate::lifetime::Lifetime;
144    use proc_macro2::{Punct, Spacing, TokenStream};
145    use quote::{ToTokens, TokenStreamExt};
146
147    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
148    impl ToTokens for Lifetime {
149        fn to_tokens(&self, tokens: &mut TokenStream) {
150            let mut apostrophe = Punct::new('\'', Spacing::Joint);
151            apostrophe.set_span(self.apostrophe);
152            tokens.append(apostrophe);
153            self.ident.to_tokens(tokens);
154        }
155    }
156}
syn/lifetime.rs

syn/
lifetime.rs
