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Error recovery in the tokeniser

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Closes #31994
This commit is contained in:
Nick Cameron 2016-03-22 16:02:09 +13:00
parent 3ee841c335
commit 2731dc169c
1 changed files with 58 additions and 25 deletions
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83
src/libsyntax/parse/parser.rs
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@ -268,8 +268,8 @@ pub struct Parser<'a> {
/// Used to determine the path to externally loaded source files
pub filename: Option<String>,
pub mod_path_stack: Vec<InternedString>,
/// Stack of spans of open delimiters. Used for error message.
pub open_braces: Vec<Span>,
/// Stack of open delimiters and their spans. Used for error message.
pub open_braces: Vec<(token::DelimToken, Span)>,
/// Flag if this parser "owns" the directory that it is currently parsing
/// in. This will affect how nested files are looked up.
pub owns_directory: bool,
@ -895,7 +895,7 @@ impl<'a> Parser<'a> {
sep: SeqSep,
f: F)
-> Vec<T>
where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
{
self.parse_seq_to_before_tokens(&[ket], sep, f, |mut e| e.emit())
}
@ -2755,8 +2755,8 @@ impl<'a> Parser<'a> {
let mut err: DiagnosticBuilder<'a> =
self.diagnostic().struct_span_err(self.span,
"this file contains an un-closed delimiter");
for sp in &self.open_braces {
err.span_help(*sp, "did you mean to close this delimiter?");
for &(_, sp) in &self.open_braces {
err.span_help(sp, "did you mean to close this delimiter?");
}
Err(err)
@ -2766,23 +2766,66 @@ impl<'a> Parser<'a> {
let pre_span = self.span;
// Parse the open delimiter.
self.open_braces.push(self.span);
self.open_braces.push((delim, self.span));
let open_span = self.span;
self.bump();
// Parse the token trees within the delimiters
let tts = self.parse_seq_to_before_end(&token::CloseDelim(delim),
SeqSep::none(),
|p| p.parse_token_tree());
// 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_seq_to_before_tokens(&[&token::CloseDelim(token::Brace),
&token::CloseDelim(token::Paren),
&token::CloseDelim(token::Bracket)],
SeqSep::none(),
|p| p.parse_token_tree(),
|mut e| e.emit());
// Parse the close delimiter.
let close_span = self.span;
self.bump();
self.open_braces.pop().unwrap();
// Expand to cover the entire delimited token tree
let span = Span { hi: close_span.hi, ..pre_span };
match self.token {
// Correct delmiter.
token::CloseDelim(d) if d == delim => {
self.open_braces.pop().unwrap();
// Parse the close delimiter.
self.bump();
}
// Incorect delimiter.
token::CloseDelim(other) => {
let token_str = self.this_token_to_string();
let mut err = self.diagnostic().struct_span_err(self.span,
&format!("incorrect close delimiter: `{}`", token_str));
// 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.open_braces.last() {
err.span_note(sp, "unclosed delimiter");
};
err.emit();
self.open_braces.pop().unwrap();
// If the incorrect delimter 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.open_braces.iter().any(|&(b, _)| b == other) {
self.bump();
}
}
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(span, Rc::new(Delimited {
delim: delim,
open_span: open_span,
@ -2798,17 +2841,7 @@ impl<'a> Parser<'a> {
maybe_whole!(deref self, NtTT);
match self.token {
token::CloseDelim(_) => {
let token_str = self.this_token_to_string();
let mut err = self.diagnostic().struct_span_err(self.span,
&format!("incorrect close delimiter: `{}`", token_str));
// 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.open_braces.last() {
err.span_note(sp, "unclosed delimiter");
};
Err(err)
panic!("should have been caught above");
},
/* we ought to allow different depths of unquotation */
token::Dollar | token::SubstNt(..) if self.quote_depth > 0 => {