crates/proc-macro-srv/src/abis/abi_1_64/proc_macro/quote.rs

   1 //! # Quasiquoter
   2 //! This file contains the implementation internals of the quasiquoter provided by `quote!`.
   3
   4 //! This quasiquoter uses macros 2.0 hygiene to reliably access
   5 //! items from `proc_macro`, to build a `proc_macro::TokenStream`.
   6
   7 use super::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
   8
   9 macro_rules! quote_tt {
  10     (($($t:tt)*)) => { Group::new(Delimiter::Parenthesis, quote!($($t)*)) };
  11     ([$($t:tt)*]) => { Group::new(Delimiter::Bracket, quote!($($t)*)) };
  12     ({$($t:tt)*}) => { Group::new(Delimiter::Brace, quote!($($t)*)) };
  13     (,) => { Punct::new(',', Spacing::Alone) };
  14     (.) => { Punct::new('.', Spacing::Alone) };
  15     (;) => { Punct::new(';', Spacing::Alone) };
  16     (!) => { Punct::new('!', Spacing::Alone) };
  17     (<) => { Punct::new('<', Spacing::Alone) };
  18     (>) => { Punct::new('>', Spacing::Alone) };
  19     (&) => { Punct::new('&', Spacing::Alone) };
  20     (=) => { Punct::new('=', Spacing::Alone) };
  21     ($i:ident) => { Ident::new(stringify!($i), Span::def_site()) };
  22 }
  23
  24 macro_rules! quote_ts {
  25     ((@ $($t:tt)*)) => { $($t)* };
  26     (::) => {
  27         [
  28             TokenTree::from(Punct::new(':', Spacing::Joint)),
  29             TokenTree::from(Punct::new(':', Spacing::Alone)),
  30         ].iter()
  31             .cloned()
  32             .map(|mut x| {
  33                 x.set_span(Span::def_site());
  34                 x
  35             })
  36             .collect::<TokenStream>()
  37     };
  38     ($t:tt) => { TokenTree::from(quote_tt!($t)) };
  39 }
  40
  41 /// Simpler version of the real `quote!` macro, implemented solely
  42 /// through `macro_rules`, for bootstrapping the real implementation
  43 /// (see the `quote` function), which does not have access to the
  44 /// real `quote!` macro due to the `proc_macro` crate not being
  45 /// able to depend on itself.
  46 ///
  47 /// Note: supported tokens are a subset of the real `quote!`, but
  48 /// unquoting is different: instead of `$x`, this uses `(@ expr)`.
  49 macro_rules! quote {
  50     () => { TokenStream::new() };
  51     ($($t:tt)*) => {
  52         [
  53             $(TokenStream::from(quote_ts!($t)),)*
  54         ].iter().cloned().collect::<TokenStream>()
  55     };
  56 }
  57
  58 /// Quote a `TokenStream` into a `TokenStream`.
  59 /// This is the actual implementation of the `quote!()` proc macro.
  60 ///
  61 /// It is loaded by the compiler in `register_builtin_macros`.
  62 pub fn quote(stream: TokenStream) -> TokenStream {
  63     if stream.is_empty() {
  64         return quote!(super::TokenStream::new());
  65     }
  66     let proc_macro_crate = quote!(crate);
  67     let mut after_dollar = false;
  68     let tokens = stream
  69         .into_iter()
  70         .filter_map(|tree| {
  71             if after_dollar {
  72                 after_dollar = false;
  73                 match tree {
  74                     TokenTree::Ident(_) => {
  75                         return Some(quote!(Into::<super::TokenStream>::into(
  76                         Clone::clone(&(@ tree))),));
  77                     }
  78                     TokenTree::Punct(ref tt) if tt.as_char() == '$' => {}
  79                     _ => panic!("`$` must be followed by an ident or `$` in `quote!`"),
  80                 }
  81             } else if let TokenTree::Punct(ref tt) = tree {
  82                 if tt.as_char() == '$' {
  83                     after_dollar = true;
  84                     return None;
  85                 }
  86             }
  87
  88             Some(quote!(super::TokenStream::from((@ match tree {
  89                 TokenTree::Punct(tt) => quote!(super::TokenTree::Punct(super::Punct::new(
  90                     (@ TokenTree::from(Literal::character(tt.as_char()))),
  91                     (@ match tt.spacing() {
  92                         Spacing::Alone => quote!(super::Spacing::Alone),
  93                         Spacing::Joint => quote!(super::Spacing::Joint),
  94                     }),
  95                 ))),
  96                 TokenTree::Group(tt) => quote!(super::TokenTree::Group(super::Group::new(
  97                     (@ match tt.delimiter() {
  98                         Delimiter::Parenthesis => quote!(super::Delimiter::Parenthesis),
  99                         Delimiter::Brace => quote!(super::Delimiter::Brace),
 100                         Delimiter::Bracket => quote!(super::Delimiter::Bracket),
 101                         Delimiter::None => quote!(super::Delimiter::None),
 102                     }),
 103                     (@ quote(tt.stream())),
 104                 ))),
 105                 TokenTree::Ident(tt) => quote!(super::TokenTree::Ident(super::Ident::new(
 106                     (@ TokenTree::from(Literal::string(&tt.to_string()))),
 107                     (@ quote_span(proc_macro_crate.clone(), tt.span())),
 108                 ))),
 109                 TokenTree::Literal(tt) => quote!(super::TokenTree::Literal({
 110                     let mut iter = (@ TokenTree::from(Literal::string(&tt.to_string())))
 111                         .parse::<super::TokenStream>()
 112                         .unwrap()
 113                         .into_iter();
 114                     if let (Some(super::TokenTree::Literal(mut lit)), None) =
 115                         (iter.next(), iter.next())
 116                     {
 117                         lit.set_span((@ quote_span(proc_macro_crate.clone(), tt.span())));
 118                         lit
 119                     } else {
 120                         unreachable!()
 121                     }
 122                 }))
 123             })),))
 124         })
 125         .collect::<TokenStream>();
 126
 127     if after_dollar {
 128         panic!("unexpected trailing `$` in `quote!`");
 129     }
 130
 131     quote!([(@ tokens)].iter().cloned().collect::<super::TokenStream>())
 132 }
 133
 134 /// Quote a `Span` into a `TokenStream`.
 135 /// This is needed to implement a custom quoter.
 136 pub fn quote_span(proc_macro_crate: TokenStream, span: Span) -> TokenStream {
 137     let id = span.save_span();
 138     quote!((@ proc_macro_crate ) ::Span::recover_proc_macro_span((@ TokenTree::from(Literal::usize_unsuffixed(id)))))
 139 }