142 lines
5.7 KiB
Rust
142 lines
5.7 KiB
Rust
//! # Quasiquoter
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//! This file contains the implementation internals of the quasiquoter provided by `quote!`.
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//! This quasiquoter uses macros 2.0 hygiene to reliably access
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//! items from `proc_macro`, to build a `proc_macro::TokenStream`.
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use crate::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
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macro_rules! quote_tt {
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(($($t:tt)*)) => { Group::new(Delimiter::Parenthesis, quote!($($t)*)) };
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([$($t:tt)*]) => { Group::new(Delimiter::Bracket, quote!($($t)*)) };
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({$($t:tt)*}) => { Group::new(Delimiter::Brace, quote!($($t)*)) };
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(,) => { Punct::new(',', Spacing::Alone) };
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(.) => { Punct::new('.', Spacing::Alone) };
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(;) => { Punct::new(';', Spacing::Alone) };
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(!) => { Punct::new('!', Spacing::Alone) };
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(<) => { Punct::new('<', Spacing::Alone) };
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(>) => { Punct::new('>', Spacing::Alone) };
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(&) => { Punct::new('&', Spacing::Alone) };
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(=) => { Punct::new('=', Spacing::Alone) };
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($i:ident) => { Ident::new(stringify!($i), Span::def_site()) };
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}
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macro_rules! quote_ts {
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((@ $($t:tt)*)) => { $($t)* };
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(::) => {
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[
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TokenTree::from(Punct::new(':', Spacing::Joint)),
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TokenTree::from(Punct::new(':', Spacing::Alone)),
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].iter()
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.cloned()
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.map(|mut x| {
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x.set_span(Span::def_site());
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x
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})
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.collect::<TokenStream>()
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};
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($t:tt) => { TokenTree::from(quote_tt!($t)) };
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}
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/// Simpler version of the real `quote!` macro, implemented solely
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/// through `macro_rules`, for bootstrapping the real implementation
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/// (see the `quote` function), which does not have access to the
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/// real `quote!` macro due to the `proc_macro` crate not being
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/// able to depend on itself.
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///
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/// Note: supported tokens are a subset of the real `quote!`, but
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/// unquoting is different: instead of `$x`, this uses `(@ expr)`.
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macro_rules! quote {
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() => { TokenStream::new() };
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($($t:tt)*) => {
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[
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$(TokenStream::from(quote_ts!($t)),)*
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].iter().cloned().collect::<TokenStream>()
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};
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}
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/// Quote a `TokenStream` into a `TokenStream`.
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/// This is the actual implementation of the `quote!()` proc macro.
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///
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/// It is loaded by the compiler in `register_builtin_macros`.
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#[unstable(feature = "proc_macro_quote", issue = "54722")]
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pub fn quote(stream: TokenStream) -> TokenStream {
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if stream.is_empty() {
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return quote!(crate::TokenStream::new());
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}
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let proc_macro_crate = quote!(crate);
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let mut after_dollar = false;
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let tokens = stream
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.into_iter()
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.filter_map(|tree| {
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if after_dollar {
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after_dollar = false;
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match tree {
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TokenTree::Ident(_) => {
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return Some(quote!(Into::<crate::TokenStream>::into(
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Clone::clone(&(@ tree))),));
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}
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TokenTree::Punct(ref tt) if tt.as_char() == '$' => {}
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_ => panic!("`$` must be followed by an ident or `$` in `quote!`"),
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}
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} else if let TokenTree::Punct(ref tt) = tree {
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if tt.as_char() == '$' {
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after_dollar = true;
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return None;
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}
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}
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Some(quote!(crate::TokenStream::from((@ match tree {
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TokenTree::Punct(tt) => quote!(crate::TokenTree::Punct(crate::Punct::new(
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(@ TokenTree::from(Literal::character(tt.as_char()))),
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(@ match tt.spacing() {
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Spacing::Alone => quote!(crate::Spacing::Alone),
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Spacing::Joint => quote!(crate::Spacing::Joint),
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}),
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))),
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TokenTree::Group(tt) => quote!(crate::TokenTree::Group(crate::Group::new(
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(@ match tt.delimiter() {
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Delimiter::Parenthesis => quote!(crate::Delimiter::Parenthesis),
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Delimiter::Brace => quote!(crate::Delimiter::Brace),
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Delimiter::Bracket => quote!(crate::Delimiter::Bracket),
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Delimiter::None => quote!(crate::Delimiter::None),
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}),
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(@ quote(tt.stream())),
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))),
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TokenTree::Ident(tt) => quote!(crate::TokenTree::Ident(crate::Ident::new(
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(@ TokenTree::from(Literal::string(&tt.to_string()))),
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(@ quote_span(proc_macro_crate.clone(), tt.span())),
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))),
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TokenTree::Literal(tt) => quote!(crate::TokenTree::Literal({
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let mut iter = (@ TokenTree::from(Literal::string(&tt.to_string())))
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.parse::<crate::TokenStream>()
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.unwrap()
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.into_iter();
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if let (Some(crate::TokenTree::Literal(mut lit)), None) =
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(iter.next(), iter.next())
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{
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lit.set_span((@ quote_span(proc_macro_crate.clone(), tt.span())));
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lit
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} else {
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unreachable!()
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}
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}))
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})),))
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})
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.collect::<TokenStream>();
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if after_dollar {
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panic!("unexpected trailing `$` in `quote!`");
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}
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quote!([(@ tokens)].iter().cloned().collect::<crate::TokenStream>())
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}
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/// Quote a `Span` into a `TokenStream`.
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/// This is needed to implement a custom quoter.
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#[unstable(feature = "proc_macro_quote", issue = "54722")]
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pub fn quote_span(proc_macro_crate: TokenStream, span: Span) -> TokenStream {
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let id = span.save_span();
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quote!((@ proc_macro_crate ) ::Span::recover_proc_macro_span((@ TokenTree::from(Literal::usize_unsuffixed(id)))))
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}
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