xref: /third_party/rust/crates/syn/src/ident.rs (revision fad3a1d3) 
1#[cfg(feature = "parsing")]
2use crate::lookahead;
3
4pub use proc_macro2::Ident;
5
6#[cfg(feature = "parsing")]
7pub_if_not_doc! {
8    #[doc(hidden)]
9    #[allow(non_snake_case)]
10    pub fn Ident(marker: lookahead::TokenMarker) -> Ident {
11        match marker {}
12    }
13}
14
15macro_rules! ident_from_token {
16    ($token:ident) => {
17        impl From<Token![$token]> for Ident {
18            fn from(token: Token![$token]) -> Ident {
19                Ident::new(stringify!($token), token.span)
20            }
21        }
22    };
23}
24
25ident_from_token!(self);
26ident_from_token!(Self);
27ident_from_token!(super);
28ident_from_token!(crate);
29ident_from_token!(extern);
30
31impl From<Token![_]> for Ident {
32    fn from(token: Token![_]) -> Ident {
33        Ident::new("_", token.span)
34    }
35}
36
37pub(crate) fn xid_ok(symbol: &str) -> bool {
38    let mut chars = symbol.chars();
39    let first = chars.next().unwrap();
40    if !(first == '_' || unicode_ident::is_xid_start(first)) {
41        return false;
42    }
43    for ch in chars {
44        if !unicode_ident::is_xid_continue(ch) {
45            return false;
46        }
47    }
48    true
49}
50
51#[cfg(feature = "parsing")]
52mod parsing {
53    use crate::buffer::Cursor;
54    use crate::parse::{Parse, ParseStream, Result};
55    use crate::token::Token;
56    use proc_macro2::Ident;
57
58    fn accept_as_ident(ident: &Ident) -> bool {
59        match ident.to_string().as_str() {
60            "_" |
61            // Based on https://doc.rust-lang.org/1.65.0/reference/keywords.html
62            "abstract" | "as" | "async" | "await" | "become" | "box" | "break" |
63            "const" | "continue" | "crate" | "do" | "dyn" | "else" | "enum" |
64            "extern" | "false" | "final" | "fn" | "for" | "if" | "impl" | "in" |
65            "let" | "loop" | "macro" | "match" | "mod" | "move" | "mut" |
66            "override" | "priv" | "pub" | "ref" | "return" | "Self" | "self" |
67            "static" | "struct" | "super" | "trait" | "true" | "try" | "type" |
68            "typeof" | "unsafe" | "unsized" | "use" | "virtual" | "where" |
69            "while" | "yield" => false,
70            _ => true,
71        }
72    }
73
74    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
75    impl Parse for Ident {
76        fn parse(input: ParseStream) -> Result<Self> {
77            input.step(|cursor| {
78                if let Some((ident, rest)) = cursor.ident() {
79                    if accept_as_ident(&ident) {
80                        Ok((ident, rest))
81                    } else {
82                        Err(cursor.error(format_args!(
83                            "expected identifier, found keyword `{}`",
84                            ident,
85                        )))
86                    }
87                } else {
88                    Err(cursor.error("expected identifier"))
89                }
90            })
91        }
92    }
93
94    impl Token for Ident {
95        fn peek(cursor: Cursor) -> bool {
96            if let Some((ident, _rest)) = cursor.ident() {
97                accept_as_ident(&ident)
98            } else {
99                false
100            }
101        }
102
103        fn display() -> &'static str {
104            "identifier"
105        }
106    }
107}
108