diff options
Diffstat (limited to 'src/librustdoc/clean/render_macro_matchers.rs')
| -rw-r--r-- | src/librustdoc/clean/render_macro_matchers.rs | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/src/librustdoc/clean/render_macro_matchers.rs b/src/librustdoc/clean/render_macro_matchers.rs new file mode 100644 index 000000000..ed7683e36 --- /dev/null +++ b/src/librustdoc/clean/render_macro_matchers.rs @@ -0,0 +1,238 @@ +use rustc_ast::token::{self, BinOpToken, Delimiter}; +use rustc_ast::tokenstream::{TokenStream, TokenTree}; +use rustc_ast_pretty::pprust::state::State as Printer; +use rustc_ast_pretty::pprust::PrintState; +use rustc_middle::ty::TyCtxt; +use rustc_session::parse::ParseSess; +use rustc_span::source_map::FilePathMapping; +use rustc_span::symbol::{kw, Ident, Symbol}; +use rustc_span::Span; + +/// Render a macro matcher in a format suitable for displaying to the user +/// as part of an item declaration. +pub(super) fn render_macro_matcher(tcx: TyCtxt<'_>, matcher: &TokenTree) -> String { + if let Some(snippet) = snippet_equal_to_token(tcx, matcher) { + // If the original source code is known, we display the matcher exactly + // as present in the source code. + return snippet; + } + + // If the matcher is macro-generated or some other reason the source code + // snippet is not available, we attempt to nicely render the token tree. + let mut printer = Printer::new(); + + // If the inner ibox fits on one line, we get: + // + // macro_rules! macroname { + // (the matcher) => {...}; + // } + // + // If the inner ibox gets wrapped, the cbox will break and get indented: + // + // macro_rules! macroname { + // ( + // the matcher ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~! + // ) => {...}; + // } + printer.cbox(8); + printer.word("("); + printer.zerobreak(); + printer.ibox(0); + match matcher { + TokenTree::Delimited(_span, _delim, tts) => print_tts(&mut printer, tts), + // Matcher which is not a Delimited is unexpected and should've failed + // to compile, but we render whatever it is wrapped in parens. + TokenTree::Token(..) => print_tt(&mut printer, matcher), + } + printer.end(); + printer.break_offset_if_not_bol(0, -4); + printer.word(")"); + printer.end(); + printer.s.eof() +} + +/// Find the source snippet for this token's Span, reparse it, and return the +/// snippet if the reparsed TokenTree matches the argument TokenTree. +fn snippet_equal_to_token(tcx: TyCtxt<'_>, matcher: &TokenTree) -> Option<String> { + // Find what rustc thinks is the source snippet. + // This may not actually be anything meaningful if this matcher was itself + // generated by a macro. + let source_map = tcx.sess.source_map(); + let span = matcher.span(); + let snippet = source_map.span_to_snippet(span).ok()?; + + // Create a Parser. + let sess = ParseSess::new(FilePathMapping::empty()); + let file_name = source_map.span_to_filename(span); + let mut parser = + match rustc_parse::maybe_new_parser_from_source_str(&sess, file_name, snippet.clone()) { + Ok(parser) => parser, + Err(diagnostics) => { + drop(diagnostics); + return None; + } + }; + + // Reparse a single token tree. + let mut reparsed_trees = match parser.parse_all_token_trees() { + Ok(reparsed_trees) => reparsed_trees, + Err(diagnostic) => { + diagnostic.cancel(); + return None; + } + }; + if reparsed_trees.len() != 1 { + return None; + } + let reparsed_tree = reparsed_trees.pop().unwrap(); + + // Compare against the original tree. + if reparsed_tree.eq_unspanned(matcher) { Some(snippet) } else { None } +} + +fn print_tt(printer: &mut Printer<'_>, tt: &TokenTree) { + match tt { + TokenTree::Token(token, _) => { + let token_str = printer.token_to_string(token); + printer.word(token_str); + if let token::DocComment(..) = token.kind { + printer.hardbreak() + } + } + TokenTree::Delimited(_span, delim, tts) => { + let open_delim = printer.token_kind_to_string(&token::OpenDelim(*delim)); + printer.word(open_delim); + if !tts.is_empty() { + if *delim == Delimiter::Brace { + printer.space(); + } + print_tts(printer, tts); + if *delim == Delimiter::Brace { + printer.space(); + } + } + let close_delim = printer.token_kind_to_string(&token::CloseDelim(*delim)); + printer.word(close_delim); + } + } +} + +fn print_tts(printer: &mut Printer<'_>, tts: &TokenStream) { + #[derive(Copy, Clone, PartialEq)] + enum State { + Start, + Dollar, + DollarIdent, + DollarIdentColon, + DollarParen, + DollarParenSep, + Pound, + PoundBang, + Ident, + Other, + } + + use State::*; + + let mut state = Start; + for tt in tts.trees() { + let (needs_space, next_state) = match &tt { + TokenTree::Token(tt, _) => match (state, &tt.kind) { + (Dollar, token::Ident(..)) => (false, DollarIdent), + (DollarIdent, token::Colon) => (false, DollarIdentColon), + (DollarIdentColon, token::Ident(..)) => (false, Other), + ( + DollarParen, + token::BinOp(BinOpToken::Plus | BinOpToken::Star) | token::Question, + ) => (false, Other), + (DollarParen, _) => (false, DollarParenSep), + (DollarParenSep, token::BinOp(BinOpToken::Plus | BinOpToken::Star)) => { + (false, Other) + } + (Pound, token::Not) => (false, PoundBang), + (_, token::Ident(symbol, /* is_raw */ false)) + if !usually_needs_space_between_keyword_and_open_delim(*symbol, tt.span) => + { + (true, Ident) + } + (_, token::Comma | token::Semi) => (false, Other), + (_, token::Dollar) => (true, Dollar), + (_, token::Pound) => (true, Pound), + (_, _) => (true, Other), + }, + TokenTree::Delimited(_, delim, _) => match (state, delim) { + (Dollar, Delimiter::Parenthesis) => (false, DollarParen), + (Pound | PoundBang, Delimiter::Bracket) => (false, Other), + (Ident, Delimiter::Parenthesis | Delimiter::Bracket) => (false, Other), + (_, _) => (true, Other), + }, + }; + if state != Start && needs_space { + printer.space(); + } + print_tt(printer, tt); + state = next_state; + } +} + +fn usually_needs_space_between_keyword_and_open_delim(symbol: Symbol, span: Span) -> bool { + let ident = Ident { name: symbol, span }; + let is_keyword = ident.is_used_keyword() || ident.is_unused_keyword(); + if !is_keyword { + // An identifier that is not a keyword usually does not need a space + // before an open delim. For example: `f(0)` or `f[0]`. + return false; + } + + match symbol { + // No space after keywords that are syntactically an expression. For + // example: a tuple struct created with `let _ = Self(0, 0)`, or if + // someone has `impl Index<MyStruct> for bool` then `true[MyStruct]`. + kw::False | kw::SelfLower | kw::SelfUpper | kw::True => false, + + // No space, as in `let _: fn();` + kw::Fn => false, + + // No space, as in `pub(crate) type T;` + kw::Pub => false, + + // No space for keywords that can end an expression, as in `fut.await()` + // where fut's Output type is `fn()`. + kw::Await => false, + + // Otherwise space after keyword. Some examples: + // + // `expr as [T; 2]` + // ^ + // `box (tuple,)` + // ^ + // `break (tuple,)` + // ^ + // `type T = dyn (Fn() -> dyn Trait) + Send;` + // ^ + // `for (tuple,) in iter {}` + // ^ + // `if (tuple,) == v {}` + // ^ + // `impl [T] {}` + // ^ + // `for x in [..] {}` + // ^ + // `let () = unit;` + // ^ + // `match [x, y] {...}` + // ^ + // `&mut (x as T)` + // ^ + // `return [];` + // ^ + // `fn f<T>() where (): Into<T>` + // ^ + // `while (a + b).what() {}` + // ^ + // `yield [];` + // ^ + _ => true, + } +} |