diff options
Diffstat (limited to 'src/libsyntax/parse/parser')
| -rw-r--r-- | src/libsyntax/parse/parser/pat.rs | 105 | ||||
| -rw-r--r-- | src/libsyntax/parse/parser/path.rs | 6 |
2 files changed, 82 insertions, 29 deletions
diff --git a/src/libsyntax/parse/parser/pat.rs b/src/libsyntax/parse/parser/pat.rs index de72f1c4d49..7eb2a73a11a 100644 --- a/src/libsyntax/parse/parser/pat.rs +++ b/src/libsyntax/parse/parser/pat.rs @@ -18,6 +18,8 @@ type Expected = Option<&'static str>; /// `Expected` for function and lambda parameter patterns. pub(super) const PARAM_EXPECTED: Expected = Some("parameter name"); +const WHILE_PARSING_OR_MSG: &str = "while parsing this or-pattern starting here"; + /// Whether or not an or-pattern should be gated when occurring in the current context. #[derive(PartialEq)] pub enum GateOr { Yes, No } @@ -40,7 +42,7 @@ impl<'a> Parser<'a> { /// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level. pub(super) fn parse_top_pat(&mut self, gate_or: GateOr) -> PResult<'a, P<Pat>> { // Allow a '|' before the pats (RFCs 1925, 2530, and 2535). - let gated_leading_vert = self.eat_or_separator() && gate_or == GateOr::Yes; + let gated_leading_vert = self.eat_or_separator(None) && gate_or == GateOr::Yes; let leading_vert_span = self.prev_span; // Parse the possibly-or-pattern. @@ -63,7 +65,7 @@ impl<'a> Parser<'a> { /// Parse the pattern for a function or function pointer parameter. /// Special recovery is provided for or-patterns and leading `|`. pub(super) fn parse_fn_param_pat(&mut self) -> PResult<'a, P<Pat>> { - self.recover_leading_vert("not allowed in a parameter pattern"); + self.recover_leading_vert(None, "not allowed in a parameter pattern"); let pat = self.parse_pat_with_or(PARAM_EXPECTED, GateOr::No, RecoverComma::No)?; if let PatKind::Or(..) = &pat.kind { @@ -90,7 +92,7 @@ impl<'a> Parser<'a> { gate_or: GateOr, rc: RecoverComma, ) -> PResult<'a, P<Pat>> { - // Parse the first pattern. + // Parse the first pattern (`p_0`). let first_pat = self.parse_pat(expected)?; self.maybe_recover_unexpected_comma(first_pat.span, rc)?; @@ -100,11 +102,12 @@ impl<'a> Parser<'a> { return Ok(first_pat) } + // Parse the patterns `p_1 | ... | p_n` where `n > 0`. let lo = first_pat.span; let mut pats = vec![first_pat]; - while self.eat_or_separator() { + while self.eat_or_separator(Some(lo)) { let pat = self.parse_pat(expected).map_err(|mut err| { - err.span_label(lo, "while parsing this or-pattern starting here"); + err.span_label(lo, WHILE_PARSING_OR_MSG); err })?; self.maybe_recover_unexpected_comma(pat.span, rc)?; @@ -122,11 +125,15 @@ impl<'a> Parser<'a> { /// Eat the or-pattern `|` separator. /// If instead a `||` token is encountered, recover and pretend we parsed `|`. - fn eat_or_separator(&mut self) -> bool { + fn eat_or_separator(&mut self, lo: Option<Span>) -> bool { + if self.recover_trailing_vert(lo) { + return false; + } + match self.token.kind { token::OrOr => { // Found `||`; Recover and pretend we parsed `|`. - self.ban_unexpected_or_or(); + self.ban_unexpected_or_or(lo); self.bump(); true } @@ -134,16 +141,49 @@ impl<'a> Parser<'a> { } } + /// Recover if `|` or `||` is the current token and we have one of the + /// tokens `=>`, `if`, `=`, `:`, `;`, `,`, `]`, `)`, or `}` ahead of us. + /// + /// These tokens all indicate that we reached the end of the or-pattern + /// list and can now reliably say that the `|` was an illegal trailing vert. + /// Note that there are more tokens such as `@` for which we know that the `|` + /// is an illegal parse. However, the user's intent is less clear in that case. + fn recover_trailing_vert(&mut self, lo: Option<Span>) -> bool { + let is_end_ahead = self.look_ahead(1, |token| match &token.kind { + token::FatArrow // e.g. `a | => 0,`. + | token::Ident(kw::If, false) // e.g. `a | if expr`. + | token::Eq // e.g. `let a | = 0`. + | token::Semi // e.g. `let a |;`. + | token::Colon // e.g. `let a | :`. + | token::Comma // e.g. `let (a |,)`. + | token::CloseDelim(token::Bracket) // e.g. `let [a | ]`. + | token::CloseDelim(token::Paren) // e.g. `let (a | )`. + | token::CloseDelim(token::Brace) => true, // e.g. `let A { f: a | }`. + _ => false, + }); + match (is_end_ahead, &self.token.kind) { + (true, token::BinOp(token::Or)) | (true, token::OrOr) => { + self.ban_illegal_vert(lo, "trailing", "not allowed in an or-pattern"); + self.bump(); + true + } + _ => false, + } + } + /// We have parsed `||` instead of `|`. Error and suggest `|` instead. - fn ban_unexpected_or_or(&mut self) { - self.struct_span_err(self.token.span, "unexpected token `||` after pattern") - .span_suggestion( - self.token.span, - "use a single `|` to separate multiple alternative patterns", - "|".to_owned(), - Applicability::MachineApplicable - ) - .emit(); + fn ban_unexpected_or_or(&mut self, lo: Option<Span>) { + let mut err = self.struct_span_err(self.token.span, "unexpected token `||` after pattern"); + err.span_suggestion( + self.token.span, + "use a single `|` to separate multiple alternative patterns", + "|".to_owned(), + Applicability::MachineApplicable + ); + if let Some(lo) = lo { + err.span_label(lo, WHILE_PARSING_OR_MSG); + } + err.emit(); } /// Some special error handling for the "top-level" patterns in a match arm, @@ -198,25 +238,38 @@ impl<'a> Parser<'a> { /// Recursive possibly-or-pattern parser with recovery for an erroneous leading `|`. /// See `parse_pat_with_or` for details on parsing or-patterns. fn parse_pat_with_or_inner(&mut self) -> PResult<'a, P<Pat>> { - self.recover_leading_vert("only allowed in a top-level pattern"); + self.recover_leading_vert(None, "only allowed in a top-level pattern"); self.parse_pat_with_or(None, GateOr::Yes, RecoverComma::No) } /// Recover if `|` or `||` is here. /// The user is thinking that a leading `|` is allowed in this position. - fn recover_leading_vert(&mut self, ctx: &str) { + fn recover_leading_vert(&mut self, lo: Option<Span>, ctx: &str) { if let token::BinOp(token::Or) | token::OrOr = self.token.kind { - let span = self.token.span; - let rm_msg = format!("remove the `{}`", pprust::token_to_string(&self.token)); - - self.struct_span_err(span, &format!("a leading `|` is {}", ctx)) - .span_suggestion(span, &rm_msg, String::new(), Applicability::MachineApplicable) - .emit(); - + self.ban_illegal_vert(lo, "leading", ctx); self.bump(); } } + /// A `|` or possibly `||` token shouldn't be here. Ban it. + fn ban_illegal_vert(&mut self, lo: Option<Span>, pos: &str, ctx: &str) { + let span = self.token.span; + let mut err = self.struct_span_err(span, &format!("a {} `|` is {}", pos, ctx)); + err.span_suggestion( + span, + &format!("remove the `{}`", pprust::token_to_string(&self.token)), + String::new(), + Applicability::MachineApplicable, + ); + if let Some(lo) = lo { + err.span_label(lo, WHILE_PARSING_OR_MSG); + } + if let token::OrOr = self.token.kind { + err.note("alternatives in or-patterns are separated with `|`, not `||`"); + } + err.emit(); + } + /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are /// allowed). fn parse_pat_with_range_pat( @@ -259,7 +312,7 @@ impl<'a> Parser<'a> { self.bump(); self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotDot), "...")? } - // At this point, token != &, &&, (, [ + // At this point, token != `&`, `&&`, `(`, `[`, `..`, `..=`, or `...`. _ => if self.eat_keyword(kw::Underscore) { // Parse _ PatKind::Wild diff --git a/src/libsyntax/parse/parser/path.rs b/src/libsyntax/parse/parser/path.rs index 463ae9124ca..ca823991a2e 100644 --- a/src/libsyntax/parse/parser/path.rs +++ b/src/libsyntax/parse/parser/path.rs @@ -114,9 +114,9 @@ impl<'a> Parser<'a> { pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, Path> { let meta_ident = match self.token.kind { token::Interpolated(ref nt) => match **nt { - token::NtMeta(ref meta) => match meta.kind { - ast::MetaItemKind::Word => Some(meta.path.clone()), - _ => None, + token::NtMeta(ref item) => match item.tokens.is_empty() { + true => Some(item.path.clone()), + false => None, }, _ => None, }, |