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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(rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(), 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,
}
}
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