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

//! # Quasiquoter
//! This file contains the implementation internals of the quasiquoter provided by `quote!`.

//! This quasiquoter uses macros 2.0 hygiene to reliably access
//! items from `proc_macro`, to build a `proc_macro::TokenStream`.

use crate::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};

macro_rules! quote_tt {
    (($($t:tt)*)) => { Group::new(Delimiter::Parenthesis, quote!($($t)*)) };
    ([$($t:tt)*]) => { Group::new(Delimiter::Bracket, quote!($($t)*)) };
    ({$($t:tt)*}) => { Group::new(Delimiter::Brace, quote!($($t)*)) };
    (,) => { Punct::new(',', Spacing::Alone) };
    (.) => { Punct::new('.', Spacing::Alone) };
    (:) => { Punct::new(':', Spacing::Alone) };
    (;) => { Punct::new(';', Spacing::Alone) };
    (!) => { Punct::new('!', Spacing::Alone) };
    (<) => { Punct::new('<', Spacing::Alone) };
    (>) => { Punct::new('>', Spacing::Alone) };
    (&) => { Punct::new('&', Spacing::Alone) };
    (=) => { Punct::new('=', Spacing::Alone) };
    ($i:ident) => { Ident::new(stringify!($i), Span::def_site()) };
}

macro_rules! quote_ts {
    ((@ $($t:tt)*)) => { $($t)* };
    (::) => {
        [
            TokenTree::from(Punct::new(':', Spacing::Joint)),
            TokenTree::from(Punct::new(':', Spacing::Alone)),
        ].iter()
            .cloned()
            .map(|mut x| {
                x.set_span(Span::def_site());
                x
            })
            .collect::<TokenStream>()
    };
    ($t:tt) => { TokenTree::from(quote_tt!($t)) };
}

/// Simpler version of the real `quote!` macro, implemented solely
/// through `macro_rules`, for bootstrapping the real implementation
/// (see the `quote` function), which does not have access to the
/// real `quote!` macro due to the `proc_macro` crate not being
/// able to depend on itself.
///
/// Note: supported tokens are a subset of the real `quote!`, but
/// unquoting is different: instead of `$x`, this uses `(@ expr)`.
macro_rules! quote {
    () => { TokenStream::new() };
    ($($t:tt)*) => {
        [
            $(TokenStream::from(quote_ts!($t)),)*
        ].iter().cloned().collect::<TokenStream>()
    };
}

/// Quote a `TokenStream` into a `TokenStream`.
/// This is the actual `quote!()` proc macro.
///
/// It is manually loaded in `CStore::load_macro_untracked`.
#[unstable(feature = "proc_macro_quote", issue = "54722")]
pub fn quote(stream: TokenStream) -> TokenStream {
    if stream.is_empty() {
        return quote!(crate::TokenStream::new());
    }
    let mut after_dollar = false;
    let tokens = stream
        .into_iter()
        .filter_map(|tree| {
            if after_dollar {
                after_dollar = false;
                match tree {
                    TokenTree::Ident(_) => {
                        return Some(quote!(Into::<crate::TokenStream>::into(
                        Clone::clone(&(@ tree))),));
                    }
                    TokenTree::Punct(ref tt) if tt.as_char() == '$' => {}
                    _ => panic!("`$` must be followed by an ident or `$` in `quote!`"),
                }
            } else if let TokenTree::Punct(ref tt) = tree {
                if tt.as_char() == '$' {
                    after_dollar = true;
                    return None;
                }
            }

            Some(quote!(crate::TokenStream::from((@ match tree {
                TokenTree::Punct(tt) => quote!(crate::TokenTree::Punct(crate::Punct::new(
                    (@ TokenTree::from(Literal::character(tt.as_char()))),
                    (@ match tt.spacing() {
                        Spacing::Alone => quote!(crate::Spacing::Alone),
                        Spacing::Joint => quote!(crate::Spacing::Joint),
                    }),
                ))),
                TokenTree::Group(tt) => quote!(crate::TokenTree::Group(crate::Group::new(
                    (@ match tt.delimiter() {
                        Delimiter::Parenthesis => quote!(crate::Delimiter::Parenthesis),
                        Delimiter::Brace => quote!(crate::Delimiter::Brace),
                        Delimiter::Bracket => quote!(crate::Delimiter::Bracket),
                        Delimiter::None => quote!(crate::Delimiter::None),
                    }),
                    (@ quote(tt.stream())),
                ))),
                TokenTree::Ident(tt) => quote!(crate::TokenTree::Ident(crate::Ident::new(
                    (@ TokenTree::from(Literal::string(&tt.to_string()))),
                    (@ quote_span(tt.span())),
                ))),
                TokenTree::Literal(tt) => quote!(crate::TokenTree::Literal({
                    let mut iter = (@ TokenTree::from(Literal::string(&tt.to_string())))
                        .parse::<crate::TokenStream>()
                        .unwrap()
                        .into_iter();
                    if let (Some(crate::TokenTree::Literal(mut lit)), None) =
                        (iter.next(), iter.next())
                    {
                        lit.set_span((@ quote_span(tt.span())));
                        lit
                    } else {
                        unreachable!()
                    }
                }))
            })),))
        })
        .collect::<TokenStream>();

    if after_dollar {
        panic!("unexpected trailing `$` in `quote!`");
    }

    quote!([(@ tokens)].iter().cloned().collect::<crate::TokenStream>())
}

/// Quote a `Span` into a `TokenStream`.
/// This is needed to implement a custom quoter.
#[unstable(feature = "proc_macro_quote", issue = "54722")]
pub fn quote_span(_: Span) -> TokenStream {
    quote!(crate::Span::def_site())
}