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use super::diagnostics::report_suspicious_mismatch_block;
use super::diagnostics::same_indentation_level;
use super::diagnostics::TokenTreeDiagInfo;
use super::{StringReader, UnmatchedDelim};
use rustc_ast::token::{self, Delimiter, Token};
use rustc_ast::tokenstream::{DelimSpan, Spacing, TokenStream, TokenTree};
use rustc_ast_pretty::pprust::token_to_string;
use rustc_errors::{PErr, PResult};
pub(super) struct TokenTreesReader<'a> {
string_reader: StringReader<'a>,
/// The "next" token, which has been obtained from the `StringReader` but
/// not yet handled by the `TokenTreesReader`.
token: Token,
diag_info: TokenTreeDiagInfo,
}
impl<'a> TokenTreesReader<'a> {
pub(super) fn parse_all_token_trees(
string_reader: StringReader<'a>,
) -> (PResult<'a, TokenStream>, Vec<UnmatchedDelim>) {
let mut tt_reader = TokenTreesReader {
string_reader,
token: Token::dummy(),
diag_info: TokenTreeDiagInfo::default(),
};
let res = tt_reader.parse_token_trees(/* is_delimited */ false);
(res, tt_reader.diag_info.unmatched_delims)
}
// Parse a stream of tokens into a list of `TokenTree`s.
fn parse_token_trees(&mut self, is_delimited: bool) -> PResult<'a, TokenStream> {
self.token = self.string_reader.next_token().0;
let mut buf = Vec::new();
loop {
match self.token.kind {
token::OpenDelim(delim) => buf.push(self.parse_token_tree_open_delim(delim)?),
token::CloseDelim(delim) => {
return if is_delimited {
Ok(TokenStream::new(buf))
} else {
Err(self.close_delim_err(delim))
};
}
token::Eof => {
return if is_delimited {
Err(self.eof_err())
} else {
Ok(TokenStream::new(buf))
};
}
_ => {
// Get the next normal token. This might require getting multiple adjacent
// single-char tokens and joining them together.
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 {
if let Some(glued) = self.token.glue(&next_tok) {
self.token = glued;
} else {
let this_spacing =
if next_tok.is_op() { Spacing::Joint } else { Spacing::Alone };
break (this_spacing, next_tok);
}
} else {
break (Spacing::Alone, next_tok);
}
};
let this_tok = std::mem::replace(&mut self.token, next_tok);
buf.push(TokenTree::Token(this_tok, this_spacing));
}
}
}
}
fn eof_err(&mut self) -> PErr<'a> {
let msg = "this file contains an unclosed delimiter";
let mut err = self.string_reader.sess.span_diagnostic.struct_span_err(self.token.span, msg);
for &(_, sp) in &self.diag_info.open_braces {
err.span_label(sp, "unclosed delimiter");
self.diag_info.unmatched_delims.push(UnmatchedDelim {
expected_delim: Delimiter::Brace,
found_delim: None,
found_span: self.token.span,
unclosed_span: Some(sp),
candidate_span: None,
});
}
if let Some((delim, _)) = self.diag_info.open_braces.last() {
report_suspicious_mismatch_block(
&mut err,
&self.diag_info,
&self.string_reader.sess.source_map(),
*delim,
)
}
err
}
fn parse_token_tree_open_delim(&mut self, open_delim: Delimiter) -> PResult<'a, TokenTree> {
// 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));
// Parse 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 tts = self.parse_token_trees(/* is_delimited */ true)?;
// Expand to cover the entire delimited token tree
let delim_span = DelimSpan::from_pair(pre_span, self.token.span);
let sm = self.string_reader.sess.source_map();
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.token = self.string_reader.next_token().0;
}
// 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 parser 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 (tok, _) = self.diag_info.open_braces.pop().unwrap();
self.diag_info.unmatched_delims.push(UnmatchedDelim {
expected_delim: tok,
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.token = self.string_reader.next_token().0;
}
}
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.
}
_ => unreachable!(),
}
Ok(TokenTree::Delimited(delim_span, open_delim, tts))
}
fn close_delim_err(&mut self, delim: Delimiter) -> PErr<'a> {
// 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.sess.span_diagnostic.struct_span_err(self.token.span, msg);
report_suspicious_mismatch_block(
&mut err,
&self.diag_info,
&self.string_reader.sess.source_map(),
delim,
);
err.span_label(self.token.span, "unexpected closing delimiter");
err
}
}