mathieu/os-rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Recover on '..X' / '..=X' / '...X' range patterns.

Browse source
This commit is contained in:
Mazdak Farrokhzad 2019-07-09 03:55:13 +02:00
parent 62b29a1e17
commit 974413fcc5
1 changed files with 46 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

52
src/libsyntax/parse/parser.rs
View file

@ -3730,6 +3730,13 @@ impl<'a> Parser<'a> {
}
}
/// Is the current token suitable as the start of a range patterns end?
fn is_pat_range_end_start(&self) -> bool {
self.token.is_path_start() // e.g. `MY_CONST`;
|| self.token == token::Dot // e.g. `.5` for recovery;
|| self.token.can_begin_literal_or_bool() // e.g. `42`.
}
// helper function to decide whether to parse as ident binding or to try to do
// something more complex like range patterns
fn parse_as_ident(&mut self) -> bool {
@ -3802,6 +3809,26 @@ impl<'a> Parser<'a> {
self.parse_pat_with_range_pat(true, expected)
}
/// Parse a range-to pattern, e.g. `..X` and `..=X` for recovery.
fn parse_pat_range_to(&mut self, re: RangeEnd, form: &str) -> PResult<'a, PatKind> {
let lo = self.prev_span;
let end = self.parse_pat_range_end()?;
let range_span = lo.to(end.span);
let begin = self.mk_expr(range_span, ExprKind::Err, ThinVec::new());
self.diagnostic()
.struct_span_err(range_span, &format!("`{}X` range patterns are not supported", form))
.span_suggestion(
range_span,
"try using the minimum value for the type",
format!("MIN{}{}", form, pprust::expr_to_string(&end)),
Applicability::HasPlaceholders,
)
.emit();
Ok(PatKind::Range(begin, end, respan(lo, re)))
}
/// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
/// allowed).
fn parse_pat_with_range_pat(
@ -3843,9 +3870,24 @@ impl<'a> Parser<'a> {
pat = PatKind::Slice(slice);
}
token::DotDot => {
// Parse `..`.
self.bump();
pat = PatKind::Rest;
pat = if self.is_pat_range_end_start() {
// Parse `..42` for recovery.
self.parse_pat_range_to(RangeEnd::Excluded, "..")?
} else {
// A rest pattern `..`.
PatKind::Rest
};
}
token::DotDotEq => {
// Parse `..=42` for recovery.
self.bump();
pat = self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotEq), "..=")?;
}
token::DotDotDot => {
// Parse `...42` for recovery.
self.bump();
pat = self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotDot), "...")?;
}
// At this point, token != &, &&, (, [
_ => if self.eat_keyword(kw::Underscore) {
@ -3915,8 +3957,7 @@ impl<'a> Parser<'a> {
let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
self.bump();
let end = self.parse_pat_range_end()?;
let op = Spanned { span: op_span, node: end_kind };
pat = PatKind::Range(begin, end, op);
pat = PatKind::Range(begin, end, respan(op_span, end_kind));
}
token::OpenDelim(token::Brace) => {
if qself.is_some() {
@ -3966,8 +4007,7 @@ impl<'a> Parser<'a> {
on a range-operator token")
};
let end = self.parse_pat_range_end()?;
let op = Spanned { span: op_span, node: end_kind };
pat = PatKind::Range(begin, end, op);
pat = PatKind::Range(begin, end, respan(op_span, end_kind))
} else {
pat = PatKind::Lit(begin);
}