rustc_parse/lexer/tokentrees.rs
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use rustc_ast::token::{self, Delimiter, Token};
use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
use rustc_ast_pretty::pprust::token_to_string;
use rustc_errors::{Applicability, PErr};
use rustc_span::symbol::kw;
use super::diagnostics::{
TokenTreeDiagInfo, report_suspicious_mismatch_block, same_indentation_level,
};
use super::{StringReader, UnmatchedDelim};
use crate::Parser;
pub(super) struct TokenTreesReader<'psess, 'src> {
string_reader: StringReader<'psess, 'src>,
/// The "next" token, which has been obtained from the `StringReader` but
/// not yet handled by the `TokenTreesReader`.
token: Token,
diag_info: TokenTreeDiagInfo,
}
impl<'psess, 'src> TokenTreesReader<'psess, 'src> {
pub(super) fn lex_all_token_trees(
string_reader: StringReader<'psess, 'src>,
) -> (TokenStream, Result<(), Vec<PErr<'psess>>>, Vec<UnmatchedDelim>) {
let mut tt_reader = TokenTreesReader {
string_reader,
token: Token::dummy(),
diag_info: TokenTreeDiagInfo::default(),
};
let (_open_spacing, stream, res) = tt_reader.lex_token_trees(/* is_delimited */ false);
(stream, res, tt_reader.diag_info.unmatched_delims)
}
// Lex into a token stream. The `Spacing` in the result is that of the
// opening delimiter.
fn lex_token_trees(
&mut self,
is_delimited: bool,
) -> (Spacing, TokenStream, Result<(), Vec<PErr<'psess>>>) {
// Move past the opening delimiter.
let (_, open_spacing) = self.bump(false);
let mut buf = Vec::new();
loop {
match self.token.kind {
token::OpenDelim(delim) => {
// Invisible delimiters cannot occur here because `TokenTreesReader` parses
// code directly from strings, with no macro expansion involved.
debug_assert!(!matches!(delim, Delimiter::Invisible(_)));
buf.push(match self.lex_token_tree_open_delim(delim) {
Ok(val) => val,
Err(errs) => return (open_spacing, TokenStream::new(buf), Err(errs)),
})
}
token::CloseDelim(delim) => {
// Invisible delimiters cannot occur here because `TokenTreesReader` parses
// code directly from strings, with no macro expansion involved.
debug_assert!(!matches!(delim, Delimiter::Invisible(_)));
return (
open_spacing,
TokenStream::new(buf),
if is_delimited { Ok(()) } else { Err(vec![self.close_delim_err(delim)]) },
);
}
token::Eof => {
return (
open_spacing,
TokenStream::new(buf),
if is_delimited { Err(vec![self.eof_err()]) } else { Ok(()) },
);
}
_ => {
// Get the next normal token.
let (this_tok, this_spacing) = self.bump(true);
buf.push(TokenTree::Token(this_tok, this_spacing));
}
}
}
}
fn eof_err(&mut self) -> PErr<'psess> {
let msg = "this file contains an unclosed delimiter";
let mut err = self.string_reader.dcx().struct_span_err(self.token.span, msg);
let unclosed_delimiter_show_limit = 5;
let len = usize::min(unclosed_delimiter_show_limit, self.diag_info.open_braces.len());
for &(_, span) in &self.diag_info.open_braces[..len] {
err.span_label(span, "unclosed delimiter");
self.diag_info.unmatched_delims.push(UnmatchedDelim {
found_delim: None,
found_span: self.token.span,
unclosed_span: Some(span),
candidate_span: None,
});
}
if let Some((_, span)) = self.diag_info.open_braces.get(unclosed_delimiter_show_limit)
&& self.diag_info.open_braces.len() >= unclosed_delimiter_show_limit + 2
{
err.span_label(
*span,
format!(
"another {} unclosed delimiters begin from here",
self.diag_info.open_braces.len() - unclosed_delimiter_show_limit
),
);
}
if let Some((delim, _)) = self.diag_info.open_braces.last() {
report_suspicious_mismatch_block(
&mut err,
&self.diag_info,
self.string_reader.psess.source_map(),
*delim,
)
}
err
}
fn lex_token_tree_open_delim(
&mut self,
open_delim: Delimiter,
) -> Result<TokenTree, Vec<PErr<'psess>>> {
// The span for beginning of the delimited section.
let pre_span = self.token.span;
self.diag_info.open_braces.push((open_delim, self.token.span));
// Lex the token trees within the delimiters.
// We stop at any delimiter so we can try to recover if the user
// uses an incorrect delimiter.
let (open_spacing, tts, res) = self.lex_token_trees(/* is_delimited */ true);
if let Err(errs) = res {
return Err(self.unclosed_delim_err(tts, errs));
}
// Expand to cover the entire delimited token tree.
let delim_span = DelimSpan::from_pair(pre_span, self.token.span);
let sm = self.string_reader.psess.source_map();
let close_spacing = match self.token.kind {
// Correct delimiter.
token::CloseDelim(close_delim) if close_delim == open_delim => {
let (open_brace, open_brace_span) = self.diag_info.open_braces.pop().unwrap();
let close_brace_span = self.token.span;
if tts.is_empty() && close_delim == Delimiter::Brace {
let empty_block_span = open_brace_span.to(close_brace_span);
if !sm.is_multiline(empty_block_span) {
// Only track if the block is in the form of `{}`, otherwise it is
// likely that it was written on purpose.
self.diag_info.empty_block_spans.push(empty_block_span);
}
}
// only add braces
if let (Delimiter::Brace, Delimiter::Brace) = (open_brace, open_delim) {
// Add all the matching spans, we will sort by span later
self.diag_info.matching_block_spans.push((open_brace_span, close_brace_span));
}
// Move past the closing delimiter.
self.bump(false).1
}
// Incorrect delimiter.
token::CloseDelim(close_delim) => {
let mut unclosed_delimiter = None;
let mut candidate = None;
if self.diag_info.last_unclosed_found_span != Some(self.token.span) {
// do not complain about the same unclosed delimiter multiple times
self.diag_info.last_unclosed_found_span = Some(self.token.span);
// This is a conservative error: only report the last unclosed
// delimiter. The previous unclosed delimiters could actually be
// closed! The lexer just hasn't gotten to them yet.
if let Some(&(_, sp)) = self.diag_info.open_braces.last() {
unclosed_delimiter = Some(sp);
};
for (brace, brace_span) in &self.diag_info.open_braces {
if same_indentation_level(sm, self.token.span, *brace_span)
&& brace == &close_delim
{
// high likelihood of these two corresponding
candidate = Some(*brace_span);
}
}
let (_, _) = self.diag_info.open_braces.pop().unwrap();
self.diag_info.unmatched_delims.push(UnmatchedDelim {
found_delim: Some(close_delim),
found_span: self.token.span,
unclosed_span: unclosed_delimiter,
candidate_span: candidate,
});
} else {
self.diag_info.open_braces.pop();
}
// If the incorrect delimiter matches an earlier opening
// delimiter, then don't consume it (it can be used to
// close the earlier one). Otherwise, consume it.
// E.g., we try to recover from:
// fn foo() {
// bar(baz(
// } // Incorrect delimiter but matches the earlier `{`
if !self.diag_info.open_braces.iter().any(|&(b, _)| b == close_delim) {
self.bump(false).1
} else {
// The choice of value here doesn't matter.
Spacing::Alone
}
}
token::Eof => {
// Silently recover, the EOF token will be seen again
// and an error emitted then. Thus we don't pop from
// self.open_braces here. The choice of spacing value here
// doesn't matter.
Spacing::Alone
}
_ => unreachable!(),
};
let spacing = DelimSpacing::new(open_spacing, close_spacing);
Ok(TokenTree::Delimited(delim_span, spacing, open_delim, tts))
}
// Move on to the next token, returning the current token and its spacing.
// Will glue adjacent single-char tokens together if `glue` is set.
fn bump(&mut self, glue: bool) -> (Token, Spacing) {
let (this_spacing, next_tok) = loop {
let (next_tok, is_next_tok_preceded_by_whitespace) = self.string_reader.next_token();
if is_next_tok_preceded_by_whitespace {
break (Spacing::Alone, next_tok);
} else if glue && let Some(glued) = self.token.glue(&next_tok) {
self.token = glued;
} else {
let this_spacing = if next_tok.is_punct() {
Spacing::Joint
} else if next_tok == token::Eof {
Spacing::Alone
} else {
Spacing::JointHidden
};
break (this_spacing, next_tok);
}
};
let this_tok = std::mem::replace(&mut self.token, next_tok);
(this_tok, this_spacing)
}
fn unclosed_delim_err(
&mut self,
tts: TokenStream,
mut errs: Vec<PErr<'psess>>,
) -> Vec<PErr<'psess>> {
// If there are unclosed delims, see if there are diff markers and if so, point them
// out instead of complaining about the unclosed delims.
let mut parser = Parser::new(self.string_reader.psess, tts, None);
let mut diff_errs = vec![];
// Suggest removing a `{` we think appears in an `if`/`while` condition.
// We want to suggest removing a `{` only if we think we're in an `if`/`while` condition,
// but we have no way of tracking this in the lexer itself, so we piggyback on the parser.
let mut in_cond = false;
while parser.token != token::Eof {
if let Err(diff_err) = parser.err_vcs_conflict_marker() {
diff_errs.push(diff_err);
} else if parser.is_keyword_ahead(0, &[kw::If, kw::While]) {
in_cond = true;
} else if matches!(
parser.token.kind,
token::CloseDelim(Delimiter::Brace) | token::FatArrow
) {
// End of the `if`/`while` body, or the end of a `match` guard.
in_cond = false;
} else if in_cond && parser.token == token::OpenDelim(Delimiter::Brace) {
// Store the `&&` and `let` to use their spans later when creating the diagnostic
let maybe_andand = parser.look_ahead(1, |t| t.clone());
let maybe_let = parser.look_ahead(2, |t| t.clone());
if maybe_andand == token::OpenDelim(Delimiter::Brace) {
// This might be the beginning of the `if`/`while` body (i.e., the end of the
// condition).
in_cond = false;
} else if maybe_andand == token::AndAnd && maybe_let.is_keyword(kw::Let) {
let mut err = parser.dcx().struct_span_err(
parser.token.span,
"found a `{` in the middle of a let-chain",
);
err.span_suggestion(
parser.token.span,
"consider removing this brace to parse the `let` as part of the same chain",
"",
Applicability::MachineApplicable,
);
err.span_label(
maybe_andand.span.to(maybe_let.span),
"you might have meant to continue the let-chain here",
);
errs.push(err);
}
}
parser.bump();
}
if !diff_errs.is_empty() {
for err in errs {
err.cancel();
}
return diff_errs;
}
errs
}
fn close_delim_err(&mut self, delim: Delimiter) -> PErr<'psess> {
// An unexpected closing delimiter (i.e., there is no matching opening delimiter).
let token_str = token_to_string(&self.token);
let msg = format!("unexpected closing delimiter: `{token_str}`");
let mut err = self.string_reader.dcx().struct_span_err(self.token.span, msg);
report_suspicious_mismatch_block(
&mut err,
&self.diag_info,
self.string_reader.psess.source_map(),
delim,
);
err.span_label(self.token.span, "unexpected closing delimiter");
err
}
}