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