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Diffstat (limited to 'library/proc_macro/src/quote.rs')
| -rw-r--r-- | library/proc_macro/src/quote.rs | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/library/proc_macro/src/quote.rs b/library/proc_macro/src/quote.rs new file mode 100644 index 000000000..04fa696d5 --- /dev/null +++ b/library/proc_macro/src/quote.rs @@ -0,0 +1,141 @@ +//! # 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) }; + ($i:ident) => { Ident::new(stringify!($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 implementation of the `quote!()` proc macro. +/// +/// It is loaded by the compiler in `register_builtin_macros`. +#[unstable(feature = "proc_macro_quote", issue = "54722")] +pub fn quote(stream: TokenStream) -> TokenStream { + if stream.is_empty() { + return quote!(crate::TokenStream::new()); + } + let proc_macro_crate = quote!(crate); + 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(proc_macro_crate.clone(), 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(proc_macro_crate.clone(), 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(proc_macro_crate: TokenStream, span: Span) -> TokenStream { + let id = span.save_span(); + quote!((@ proc_macro_crate ) ::Span::recover_proc_macro_span((@ TokenTree::from(Literal::usize_unsuffixed(id))))) +} |