| use super::{ForceCollect, Parser, PathStyle, TrailingToken}; |
| use crate::errors::RemoveLet; |
| use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole}; |
| use rustc_ast::mut_visit::{noop_visit_pat, MutVisitor}; |
| use rustc_ast::ptr::P; |
| use rustc_ast::token::{self, Delimiter}; |
| use rustc_ast::{ |
| self as ast, AttrVec, BindingAnnotation, ByRef, Expr, ExprKind, MacCall, Mutability, Pat, |
| PatField, PatKind, Path, QSelf, RangeEnd, RangeSyntax, |
| }; |
| use rustc_ast_pretty::pprust; |
| use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult}; |
| use rustc_session::errors::ExprParenthesesNeeded; |
| use rustc_span::source_map::{respan, Span, Spanned}; |
| use rustc_span::symbol::{kw, sym, Ident}; |
| |
| pub(super) 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 to recover a `,` when parsing or-patterns. |
| #[derive(PartialEq, Copy, Clone)] |
| pub enum RecoverComma { |
| Yes, |
| No, |
| } |
| |
| /// Whether or not to recover a `:` when parsing patterns that were meant to be paths. |
| #[derive(PartialEq, Copy, Clone)] |
| pub enum RecoverColon { |
| Yes, |
| No, |
| } |
| |
| /// Whether or not to recover a `a, b` when parsing patterns as `(a, b)` or that *and* `a | b`. |
| #[derive(PartialEq, Copy, Clone)] |
| pub enum CommaRecoveryMode { |
| LikelyTuple, |
| EitherTupleOrPipe, |
| } |
| |
| /// The result of `eat_or_separator`. We want to distinguish which case we are in to avoid |
| /// emitting duplicate diagnostics. |
| #[derive(Debug, Clone, Copy)] |
| enum EatOrResult { |
| /// We recovered from a trailing vert. |
| TrailingVert, |
| /// We ate an `|` (or `||` and recovered). |
| AteOr, |
| /// We did not eat anything (i.e. the current token is not `|` or `||`). |
| None, |
| } |
| |
| impl<'a> Parser<'a> { |
| /// Parses a pattern. |
| /// |
| /// Corresponds to `pat<no_top_alt>` in RFC 2535 and does not admit or-patterns |
| /// at the top level. Used when parsing the parameters of lambda expressions, |
| /// functions, function pointers, and `pat` macro fragments. |
| pub fn parse_pat_no_top_alt(&mut self, expected: Expected) -> PResult<'a, P<Pat>> { |
| self.parse_pat_with_range_pat(true, expected) |
| } |
| |
| /// Parses a pattern. |
| /// |
| /// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level. |
| /// Used for parsing patterns in all cases when `pat<no_top_alt>` is not used. |
| /// |
| /// Note that after the FCP in <https://github.com/rust-lang/rust/issues/81415>, |
| /// a leading vert is allowed in nested or-patterns, too. This allows us to |
| /// simplify the grammar somewhat. |
| pub fn parse_pat_allow_top_alt( |
| &mut self, |
| expected: Expected, |
| rc: RecoverComma, |
| ra: RecoverColon, |
| rt: CommaRecoveryMode, |
| ) -> PResult<'a, P<Pat>> { |
| self.parse_pat_allow_top_alt_inner(expected, rc, ra, rt).map(|(pat, _)| pat) |
| } |
| |
| /// Returns the pattern and a bool indicating whether we recovered from a trailing vert (true = |
| /// recovered). |
| fn parse_pat_allow_top_alt_inner( |
| &mut self, |
| expected: Expected, |
| rc: RecoverComma, |
| ra: RecoverColon, |
| rt: CommaRecoveryMode, |
| ) -> PResult<'a, (P<Pat>, bool)> { |
| // Keep track of whether we recovered from a trailing vert so that we can avoid duplicated |
| // suggestions (which bothers rustfix). |
| // |
| // Allow a '|' before the pats (RFCs 1925, 2530, and 2535). |
| let (leading_vert_span, mut trailing_vert) = match self.eat_or_separator(None) { |
| EatOrResult::AteOr => (Some(self.prev_token.span), false), |
| EatOrResult::TrailingVert => (None, true), |
| EatOrResult::None => (None, false), |
| }; |
| |
| // Parse the first pattern (`p_0`). |
| let mut first_pat = self.parse_pat_no_top_alt(expected)?; |
| if rc == RecoverComma::Yes { |
| self.maybe_recover_unexpected_comma(first_pat.span, rt)?; |
| } |
| |
| // If the next token is not a `|`, |
| // this is not an or-pattern and we should exit here. |
| if !self.check(&token::BinOp(token::Or)) && self.token != token::OrOr { |
| // If we parsed a leading `|` which should be gated, |
| // then we should really gate the leading `|`. |
| // This complicated procedure is done purely for diagnostics UX. |
| |
| // Check if the user wrote `foo:bar` instead of `foo::bar`. |
| if ra == RecoverColon::Yes { |
| first_pat = self.maybe_recover_colon_colon_in_pat_typo(first_pat, expected); |
| } |
| |
| if let Some(leading_vert_span) = leading_vert_span { |
| // If there was a leading vert, treat this as an or-pattern. This improves |
| // diagnostics. |
| let span = leading_vert_span.to(self.prev_token.span); |
| return Ok((self.mk_pat(span, PatKind::Or(vec![first_pat])), trailing_vert)); |
| } |
| |
| return Ok((first_pat, trailing_vert)); |
| } |
| |
| // Parse the patterns `p_1 | ... | p_n` where `n > 0`. |
| let lo = leading_vert_span.unwrap_or(first_pat.span); |
| let mut pats = vec![first_pat]; |
| loop { |
| match self.eat_or_separator(Some(lo)) { |
| EatOrResult::AteOr => {} |
| EatOrResult::None => break, |
| EatOrResult::TrailingVert => { |
| trailing_vert = true; |
| break; |
| } |
| } |
| let pat = self.parse_pat_no_top_alt(expected).map_err(|mut err| { |
| err.span_label(lo, WHILE_PARSING_OR_MSG); |
| err |
| })?; |
| if rc == RecoverComma::Yes { |
| self.maybe_recover_unexpected_comma(pat.span, rt)?; |
| } |
| pats.push(pat); |
| } |
| let or_pattern_span = lo.to(self.prev_token.span); |
| |
| Ok((self.mk_pat(or_pattern_span, PatKind::Or(pats)), trailing_vert)) |
| } |
| |
| /// Parse a pattern and (maybe) a `Colon` in positions where a pattern may be followed by a |
| /// type annotation (e.g. for `let` bindings or `fn` params). |
| /// |
| /// Generally, this corresponds to `pat_no_top_alt` followed by an optional `Colon`. It will |
| /// eat the `Colon` token if one is present. |
| /// |
| /// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false` |
| /// otherwise). |
| pub(super) fn parse_pat_before_ty( |
| &mut self, |
| expected: Expected, |
| rc: RecoverComma, |
| syntax_loc: &str, |
| ) -> PResult<'a, (P<Pat>, bool)> { |
| // We use `parse_pat_allow_top_alt` regardless of whether we actually want top-level |
| // or-patterns so that we can detect when a user tries to use it. This allows us to print a |
| // better error message. |
| let (pat, trailing_vert) = self.parse_pat_allow_top_alt_inner( |
| expected, |
| rc, |
| RecoverColon::No, |
| CommaRecoveryMode::LikelyTuple, |
| )?; |
| let colon = self.eat(&token::Colon); |
| |
| if let PatKind::Or(pats) = &pat.kind { |
| let msg = format!("top-level or-patterns are not allowed in {}", syntax_loc); |
| let (help, fix) = if pats.len() == 1 { |
| // If all we have is a leading vert, then print a special message. This is the case |
| // if `parse_pat_allow_top_alt` returns an or-pattern with one variant. |
| let msg = "remove the `|`"; |
| let fix = pprust::pat_to_string(&pat); |
| (msg, fix) |
| } else { |
| let msg = "wrap the pattern in parentheses"; |
| let fix = format!("({})", pprust::pat_to_string(&pat)); |
| (msg, fix) |
| }; |
| |
| if trailing_vert { |
| // We already emitted an error and suggestion to remove the trailing vert. Don't |
| // emit again. |
| self.sess.span_diagnostic.delay_span_bug(pat.span, &msg); |
| } else { |
| self.struct_span_err(pat.span, &msg) |
| .span_suggestion(pat.span, help, fix, Applicability::MachineApplicable) |
| .emit(); |
| } |
| } |
| |
| Ok((pat, colon)) |
| } |
| |
| /// Parse the pattern for a function or function pointer parameter, followed by a colon. |
| /// |
| /// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false` |
| /// otherwise). |
| pub(super) fn parse_fn_param_pat_colon(&mut self) -> PResult<'a, (P<Pat>, bool)> { |
| // In order to get good UX, we first recover in the case of a leading vert for an illegal |
| // top-level or-pat. Normally, this means recovering both `|` and `||`, but in this case, |
| // a leading `||` probably doesn't indicate an or-pattern attempt, so we handle that |
| // separately. |
| if let token::OrOr = self.token.kind { |
| let span = self.token.span; |
| let mut err = self.struct_span_err(span, "unexpected `||` before function parameter"); |
| err.span_suggestion(span, "remove the `||`", "", Applicability::MachineApplicable); |
| err.note("alternatives in or-patterns are separated with `|`, not `||`"); |
| err.emit(); |
| self.bump(); |
| } |
| |
| self.parse_pat_before_ty(PARAM_EXPECTED, RecoverComma::No, "function parameters") |
| } |
| |
| /// Eat the or-pattern `|` separator. |
| /// If instead a `||` token is encountered, recover and pretend we parsed `|`. |
| fn eat_or_separator(&mut self, lo: Option<Span>) -> EatOrResult { |
| if self.recover_trailing_vert(lo) { |
| EatOrResult::TrailingVert |
| } else if matches!(self.token.kind, token::OrOr) { |
| // Found `||`; Recover and pretend we parsed `|`. |
| self.ban_unexpected_or_or(lo); |
| self.bump(); |
| EatOrResult::AteOr |
| } else if self.eat(&token::BinOp(token::Or)) { |
| EatOrResult::AteOr |
| } else { |
| EatOrResult::None |
| } |
| } |
| |
| /// 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| { |
| matches!( |
| &token.uninterpolate().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(Delimiter::Bracket) // e.g. `let [a | ]`. |
| | token::CloseDelim(Delimiter::Parenthesis) // e.g. `let (a | )`. |
| | token::CloseDelim(Delimiter::Brace) // e.g. `let A { f: a | }`. |
| ) |
| }); |
| match (is_end_ahead, &self.token.kind) { |
| (true, token::BinOp(token::Or) | 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, lo: Option<Span>) { |
| let mut err = self.struct_span_err(self.token.span, "unexpected token `||` in pattern"); |
| err.span_suggestion( |
| self.token.span, |
| "use a single `|` to separate multiple alternative patterns", |
| "|", |
| Applicability::MachineApplicable, |
| ); |
| if let Some(lo) = lo { |
| err.span_label(lo, WHILE_PARSING_OR_MSG); |
| } |
| err.emit(); |
| } |
| |
| /// 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)), |
| "", |
| 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( |
| &mut self, |
| allow_range_pat: bool, |
| expected: Expected, |
| ) -> PResult<'a, P<Pat>> { |
| maybe_recover_from_interpolated_ty_qpath!(self, true); |
| maybe_whole!(self, NtPat, |x| x); |
| |
| let mut lo = self.token.span; |
| |
| if self.token.is_keyword(kw::Let) && self.look_ahead(1, |tok| tok.can_begin_pattern()) { |
| self.bump(); |
| self.sess.emit_err(RemoveLet { span: lo }); |
| lo = self.token.span; |
| } |
| |
| let pat = if self.check(&token::BinOp(token::And)) || self.token.kind == token::AndAnd { |
| self.parse_pat_deref(expected)? |
| } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) { |
| self.parse_pat_tuple_or_parens()? |
| } else if self.check(&token::OpenDelim(Delimiter::Bracket)) { |
| // Parse `[pat, pat,...]` as a slice pattern. |
| let (pats, _) = self.parse_delim_comma_seq(Delimiter::Bracket, |p| { |
| p.parse_pat_allow_top_alt( |
| None, |
| RecoverComma::No, |
| RecoverColon::No, |
| CommaRecoveryMode::EitherTupleOrPipe, |
| ) |
| })?; |
| PatKind::Slice(pats) |
| } else if self.check(&token::DotDot) && !self.is_pat_range_end_start(1) { |
| // A rest pattern `..`. |
| self.bump(); // `..` |
| PatKind::Rest |
| } else if self.check(&token::DotDotDot) && !self.is_pat_range_end_start(1) { |
| self.recover_dotdotdot_rest_pat(lo) |
| } else if let Some(form) = self.parse_range_end() { |
| self.parse_pat_range_to(form)? // `..=X`, `...X`, or `..X`. |
| } else if self.eat_keyword(kw::Underscore) { |
| // Parse _ |
| PatKind::Wild |
| } else if self.eat_keyword(kw::Mut) { |
| self.parse_pat_ident_mut()? |
| } else if self.eat_keyword(kw::Ref) { |
| // Parse ref ident @ pat / ref mut ident @ pat |
| let mutbl = self.parse_mutability(); |
| self.parse_pat_ident(BindingAnnotation(ByRef::Yes, mutbl))? |
| } else if self.eat_keyword(kw::Box) { |
| self.parse_pat_box()? |
| } else if self.check_inline_const(0) { |
| // Parse `const pat` |
| let const_expr = self.parse_const_block(lo.to(self.token.span), true)?; |
| |
| if let Some(re) = self.parse_range_end() { |
| self.parse_pat_range_begin_with(const_expr, re)? |
| } else { |
| PatKind::Lit(const_expr) |
| } |
| } else if self.can_be_ident_pat() { |
| // Parse `ident @ pat` |
| // This can give false positives and parse nullary enums, |
| // they are dealt with later in resolve. |
| self.parse_pat_ident(BindingAnnotation::NONE)? |
| } else if self.is_start_of_pat_with_path() { |
| // Parse pattern starting with a path |
| let (qself, path) = if self.eat_lt() { |
| // Parse a qualified path |
| let (qself, path) = self.parse_qpath(PathStyle::Expr)?; |
| (Some(qself), path) |
| } else { |
| // Parse an unqualified path |
| (None, self.parse_path(PathStyle::Expr)?) |
| }; |
| let span = lo.to(self.prev_token.span); |
| |
| if qself.is_none() && self.check(&token::Not) { |
| self.parse_pat_mac_invoc(path)? |
| } else if let Some(form) = self.parse_range_end() { |
| let begin = self.mk_expr(span, ExprKind::Path(qself, path)); |
| self.parse_pat_range_begin_with(begin, form)? |
| } else if self.check(&token::OpenDelim(Delimiter::Brace)) { |
| self.parse_pat_struct(qself, path)? |
| } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) { |
| self.parse_pat_tuple_struct(qself, path)? |
| } else { |
| PatKind::Path(qself, path) |
| } |
| } else if matches!(self.token.kind, token::Lifetime(_)) |
| // In pattern position, we're totally fine with using "next token isn't colon" |
| // as a heuristic. We could probably just always try to recover if it's a lifetime, |
| // because we never have `'a: label {}` in a pattern position anyways, but it does |
| // keep us from suggesting something like `let 'a: Ty = ..` => `let 'a': Ty = ..` |
| && !self.look_ahead(1, |token| matches!(token.kind, token::Colon)) |
| { |
| // Recover a `'a` as a `'a'` literal |
| let lt = self.expect_lifetime(); |
| let lit = self.recover_unclosed_char(lt.ident, |self_| { |
| let expected = expected.unwrap_or("pattern"); |
| let msg = |
| format!("expected {}, found {}", expected, super::token_descr(&self_.token)); |
| |
| let mut err = self_.struct_span_err(self_.token.span, &msg); |
| err.span_label(self_.token.span, format!("expected {}", expected)); |
| err |
| }); |
| PatKind::Lit(self.mk_expr(lo, ExprKind::Lit(lit))) |
| } else { |
| // Try to parse everything else as literal with optional minus |
| match self.parse_literal_maybe_minus() { |
| Ok(begin) => match self.parse_range_end() { |
| Some(form) => self.parse_pat_range_begin_with(begin, form)?, |
| None => PatKind::Lit(begin), |
| }, |
| Err(err) => return self.fatal_unexpected_non_pat(err, expected), |
| } |
| }; |
| |
| let pat = self.mk_pat(lo.to(self.prev_token.span), pat); |
| let pat = self.maybe_recover_from_bad_qpath(pat)?; |
| let pat = self.recover_intersection_pat(pat)?; |
| |
| if !allow_range_pat { |
| self.ban_pat_range_if_ambiguous(&pat) |
| } |
| |
| Ok(pat) |
| } |
| |
| /// Recover from a typoed `...` pattern that was encountered |
| /// Ref: Issue #70388 |
| fn recover_dotdotdot_rest_pat(&mut self, lo: Span) -> PatKind { |
| // A typoed rest pattern `...`. |
| self.bump(); // `...` |
| |
| // The user probably mistook `...` for a rest pattern `..`. |
| self.struct_span_err(lo, "unexpected `...`") |
| .span_label(lo, "not a valid pattern") |
| .span_suggestion_short( |
| lo, |
| "for a rest pattern, use `..` instead of `...`", |
| "..", |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| PatKind::Rest |
| } |
| |
| /// Try to recover the more general form `intersect ::= $pat_lhs @ $pat_rhs`. |
| /// |
| /// Allowed binding patterns generated by `binding ::= ref? mut? $ident @ $pat_rhs` |
| /// should already have been parsed by now at this point, |
| /// if the next token is `@` then we can try to parse the more general form. |
| /// |
| /// Consult `parse_pat_ident` for the `binding` grammar. |
| /// |
| /// The notion of intersection patterns are found in |
| /// e.g. [F#][and] where they are called AND-patterns. |
| /// |
| /// [and]: https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/pattern-matching |
| fn recover_intersection_pat(&mut self, lhs: P<Pat>) -> PResult<'a, P<Pat>> { |
| if self.token.kind != token::At { |
| // Next token is not `@` so it's not going to be an intersection pattern. |
| return Ok(lhs); |
| } |
| |
| // At this point we attempt to parse `@ $pat_rhs` and emit an error. |
| self.bump(); // `@` |
| let mut rhs = self.parse_pat_no_top_alt(None)?; |
| let sp = lhs.span.to(rhs.span); |
| |
| if let PatKind::Ident(_, _, ref mut sub @ None) = rhs.kind { |
| // The user inverted the order, so help them fix that. |
| let mut applicability = Applicability::MachineApplicable; |
| // FIXME(bindings_after_at): Remove this code when stabilizing the feature. |
| lhs.walk(&mut |p| match p.kind { |
| // `check_match` is unhappy if the subpattern has a binding anywhere. |
| PatKind::Ident(..) => { |
| applicability = Applicability::MaybeIncorrect; |
| false // Short-circuit. |
| } |
| _ => true, |
| }); |
| |
| let lhs_span = lhs.span; |
| // Move the LHS into the RHS as a subpattern. |
| // The RHS is now the full pattern. |
| *sub = Some(lhs); |
| |
| self.struct_span_err(sp, "pattern on wrong side of `@`") |
| .span_label(lhs_span, "pattern on the left, should be on the right") |
| .span_label(rhs.span, "binding on the right, should be on the left") |
| .span_suggestion(sp, "switch the order", pprust::pat_to_string(&rhs), applicability) |
| .emit(); |
| } else { |
| // The special case above doesn't apply so we may have e.g. `A(x) @ B(y)`. |
| rhs.kind = PatKind::Wild; |
| self.struct_span_err(sp, "left-hand side of `@` must be a binding") |
| .span_label(lhs.span, "interpreted as a pattern, not a binding") |
| .span_label(rhs.span, "also a pattern") |
| .note("bindings are `x`, `mut x`, `ref x`, and `ref mut x`") |
| .emit(); |
| } |
| |
| rhs.span = sp; |
| Ok(rhs) |
| } |
| |
| /// Ban a range pattern if it has an ambiguous interpretation. |
| fn ban_pat_range_if_ambiguous(&self, pat: &Pat) { |
| match pat.kind { |
| PatKind::Range( |
| .., |
| Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }, |
| ) => return, |
| PatKind::Range(..) => {} |
| _ => return, |
| } |
| |
| self.struct_span_err(pat.span, "the range pattern here has ambiguous interpretation") |
| .span_suggestion( |
| pat.span, |
| "add parentheses to clarify the precedence", |
| format!("({})", pprust::pat_to_string(&pat)), |
| // "ambiguous interpretation" implies that we have to be guessing |
| Applicability::MaybeIncorrect, |
| ) |
| .emit(); |
| } |
| |
| /// Parse `&pat` / `&mut pat`. |
| fn parse_pat_deref(&mut self, expected: Expected) -> PResult<'a, PatKind> { |
| self.expect_and()?; |
| self.recover_lifetime_in_deref_pat(); |
| let mutbl = self.parse_mutability(); |
| let subpat = self.parse_pat_with_range_pat(false, expected)?; |
| Ok(PatKind::Ref(subpat, mutbl)) |
| } |
| |
| fn recover_lifetime_in_deref_pat(&mut self) { |
| if let token::Lifetime(name) = self.token.kind { |
| self.bump(); // `'a` |
| |
| let span = self.prev_token.span; |
| self.struct_span_err(span, &format!("unexpected lifetime `{}` in pattern", name)) |
| .span_suggestion(span, "remove the lifetime", "", Applicability::MachineApplicable) |
| .emit(); |
| } |
| } |
| |
| /// Parse a tuple or parenthesis pattern. |
| fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> { |
| let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| { |
| p.parse_pat_allow_top_alt( |
| None, |
| RecoverComma::No, |
| RecoverColon::No, |
| CommaRecoveryMode::LikelyTuple, |
| ) |
| })?; |
| |
| // Here, `(pat,)` is a tuple pattern. |
| // For backward compatibility, `(..)` is a tuple pattern as well. |
| Ok(if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) { |
| PatKind::Paren(fields.into_iter().next().unwrap()) |
| } else { |
| PatKind::Tuple(fields) |
| }) |
| } |
| |
| /// Parse a mutable binding with the `mut` token already eaten. |
| fn parse_pat_ident_mut(&mut self) -> PResult<'a, PatKind> { |
| let mut_span = self.prev_token.span; |
| |
| if self.eat_keyword(kw::Ref) { |
| return self.recover_mut_ref_ident(mut_span); |
| } |
| |
| self.recover_additional_muts(); |
| |
| // Make sure we don't allow e.g. `let mut $p;` where `$p:pat`. |
| if let token::Interpolated(ref nt) = self.token.kind { |
| if let token::NtPat(_) = **nt { |
| self.expected_ident_found().emit(); |
| } |
| } |
| |
| // Parse the pattern we hope to be an identifier. |
| let mut pat = self.parse_pat_no_top_alt(Some("identifier"))?; |
| |
| // If we don't have `mut $ident (@ pat)?`, error. |
| if let PatKind::Ident(BindingAnnotation(ByRef::No, m @ Mutability::Not), ..) = &mut pat.kind |
| { |
| // Don't recurse into the subpattern. |
| // `mut` on the outer binding doesn't affect the inner bindings. |
| *m = Mutability::Mut; |
| } else { |
| // Add `mut` to any binding in the parsed pattern. |
| let changed_any_binding = Self::make_all_value_bindings_mutable(&mut pat); |
| self.ban_mut_general_pat(mut_span, &pat, changed_any_binding); |
| } |
| |
| Ok(pat.into_inner().kind) |
| } |
| |
| /// Recover on `mut ref? ident @ pat` and suggest |
| /// that the order of `mut` and `ref` is incorrect. |
| fn recover_mut_ref_ident(&mut self, lo: Span) -> PResult<'a, PatKind> { |
| let mutref_span = lo.to(self.prev_token.span); |
| self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect") |
| .span_suggestion( |
| mutref_span, |
| "try switching the order", |
| "ref mut", |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| |
| self.parse_pat_ident(BindingAnnotation::REF_MUT) |
| } |
| |
| /// Turn all by-value immutable bindings in a pattern into mutable bindings. |
| /// Returns `true` if any change was made. |
| fn make_all_value_bindings_mutable(pat: &mut P<Pat>) -> bool { |
| struct AddMut(bool); |
| impl MutVisitor for AddMut { |
| fn visit_pat(&mut self, pat: &mut P<Pat>) { |
| if let PatKind::Ident(BindingAnnotation(ByRef::No, m @ Mutability::Not), ..) = |
| &mut pat.kind |
| { |
| self.0 = true; |
| *m = Mutability::Mut; |
| } |
| noop_visit_pat(pat, self); |
| } |
| } |
| |
| let mut add_mut = AddMut(false); |
| add_mut.visit_pat(pat); |
| add_mut.0 |
| } |
| |
| /// Error on `mut $pat` where `$pat` is not an ident. |
| fn ban_mut_general_pat(&self, lo: Span, pat: &Pat, changed_any_binding: bool) { |
| let span = lo.to(pat.span); |
| let fix = pprust::pat_to_string(&pat); |
| let (problem, suggestion) = if changed_any_binding { |
| ("`mut` must be attached to each individual binding", "add `mut` to each binding") |
| } else { |
| ("`mut` must be followed by a named binding", "remove the `mut` prefix") |
| }; |
| self.struct_span_err(span, problem) |
| .span_suggestion(span, suggestion, fix, Applicability::MachineApplicable) |
| .note("`mut` may be followed by `variable` and `variable @ pattern`") |
| .emit(); |
| } |
| |
| /// Eat any extraneous `mut`s and error + recover if we ate any. |
| fn recover_additional_muts(&mut self) { |
| let lo = self.token.span; |
| while self.eat_keyword(kw::Mut) {} |
| if lo == self.token.span { |
| return; |
| } |
| |
| let span = lo.to(self.prev_token.span); |
| self.struct_span_err(span, "`mut` on a binding may not be repeated") |
| .span_suggestion( |
| span, |
| "remove the additional `mut`s", |
| "", |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| |
| /// Parse macro invocation |
| fn parse_pat_mac_invoc(&mut self, path: Path) -> PResult<'a, PatKind> { |
| self.bump(); |
| let args = self.parse_mac_args()?; |
| let mac = P(MacCall { path, args, prior_type_ascription: self.last_type_ascription }); |
| Ok(PatKind::MacCall(mac)) |
| } |
| |
| fn fatal_unexpected_non_pat( |
| &mut self, |
| err: DiagnosticBuilder<'a, ErrorGuaranteed>, |
| expected: Expected, |
| ) -> PResult<'a, P<Pat>> { |
| err.cancel(); |
| |
| let expected = expected.unwrap_or("pattern"); |
| let msg = format!("expected {}, found {}", expected, super::token_descr(&self.token)); |
| |
| let mut err = self.struct_span_err(self.token.span, &msg); |
| err.span_label(self.token.span, format!("expected {}", expected)); |
| |
| let sp = self.sess.source_map().start_point(self.token.span); |
| if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) { |
| err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp)); |
| } |
| |
| Err(err) |
| } |
| |
| /// Parses the range pattern end form `".." | "..." | "..=" ;`. |
| fn parse_range_end(&mut self) -> Option<Spanned<RangeEnd>> { |
| let re = if self.eat(&token::DotDotDot) { |
| RangeEnd::Included(RangeSyntax::DotDotDot) |
| } else if self.eat(&token::DotDotEq) { |
| RangeEnd::Included(RangeSyntax::DotDotEq) |
| } else if self.eat(&token::DotDot) { |
| RangeEnd::Excluded |
| } else { |
| return None; |
| }; |
| Some(respan(self.prev_token.span, re)) |
| } |
| |
| /// Parse a range pattern `$begin $form $end?` where `$form = ".." | "..." | "..=" ;`. |
| /// `$begin $form` has already been parsed. |
| fn parse_pat_range_begin_with( |
| &mut self, |
| begin: P<Expr>, |
| re: Spanned<RangeEnd>, |
| ) -> PResult<'a, PatKind> { |
| let end = if self.is_pat_range_end_start(0) { |
| // Parsing e.g. `X..=Y`. |
| Some(self.parse_pat_range_end()?) |
| } else { |
| // Parsing e.g. `X..`. |
| if let RangeEnd::Included(_) = re.node { |
| // FIXME(Centril): Consider semantic errors instead in `ast_validation`. |
| self.inclusive_range_with_incorrect_end(re.span); |
| } |
| None |
| }; |
| Ok(PatKind::Range(Some(begin), end, re)) |
| } |
| |
| pub(super) fn inclusive_range_with_incorrect_end(&mut self, span: Span) { |
| let tok = &self.token; |
| |
| // If the user typed "..==" instead of "..=", we want to give them |
| // a specific error message telling them to use "..=". |
| // Otherwise, we assume that they meant to type a half open exclusive |
| // range and give them an error telling them to do that instead. |
| if matches!(tok.kind, token::Eq) && tok.span.lo() == span.hi() { |
| let span_with_eq = span.to(tok.span); |
| |
| // Ensure the user doesn't receive unhelpful unexpected token errors |
| self.bump(); |
| if self.is_pat_range_end_start(0) { |
| let _ = self.parse_pat_range_end().map_err(|e| e.cancel()); |
| } |
| |
| self.error_inclusive_range_with_extra_equals(span_with_eq); |
| } else { |
| self.error_inclusive_range_with_no_end(span); |
| } |
| } |
| |
| fn error_inclusive_range_with_extra_equals(&self, span: Span) { |
| self.struct_span_err(span, "unexpected `=` after inclusive range") |
| .span_suggestion_short(span, "use `..=` instead", "..=", Applicability::MaybeIncorrect) |
| .note("inclusive ranges end with a single equals sign (`..=`)") |
| .emit(); |
| } |
| |
| fn error_inclusive_range_with_no_end(&self, span: Span) { |
| struct_span_err!(self.sess.span_diagnostic, span, E0586, "inclusive range with no end") |
| .span_suggestion_short(span, "use `..` instead", "..", Applicability::MachineApplicable) |
| .note("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)") |
| .emit(); |
| } |
| |
| /// Parse a range-to pattern, `..X` or `..=X` where `X` remains to be parsed. |
| /// |
| /// The form `...X` is prohibited to reduce confusion with the potential |
| /// expression syntax `...expr` for splatting in expressions. |
| fn parse_pat_range_to(&mut self, mut re: Spanned<RangeEnd>) -> PResult<'a, PatKind> { |
| let end = self.parse_pat_range_end()?; |
| if let RangeEnd::Included(ref mut syn @ RangeSyntax::DotDotDot) = &mut re.node { |
| *syn = RangeSyntax::DotDotEq; |
| self.struct_span_err(re.span, "range-to patterns with `...` are not allowed") |
| .span_suggestion_short( |
| re.span, |
| "use `..=` instead", |
| "..=", |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| Ok(PatKind::Range(None, Some(end), re)) |
| } |
| |
| /// Is the token `dist` away from the current suitable as the start of a range patterns end? |
| fn is_pat_range_end_start(&self, dist: usize) -> bool { |
| self.check_inline_const(dist) |
| || self.look_ahead(dist, |t| { |
| t.is_path_start() // e.g. `MY_CONST`; |
| || t.kind == token::Dot // e.g. `.5` for recovery; |
| || t.can_begin_literal_maybe_minus() // e.g. `42`. |
| || t.is_whole_expr() |
| || t.is_lifetime() // recover `'a` instead of `'a'` |
| }) |
| } |
| |
| fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> { |
| if self.check_inline_const(0) { |
| self.parse_const_block(self.token.span, true) |
| } else if self.check_path() { |
| let lo = self.token.span; |
| let (qself, path) = if self.eat_lt() { |
| // Parse a qualified path |
| let (qself, path) = self.parse_qpath(PathStyle::Expr)?; |
| (Some(qself), path) |
| } else { |
| // Parse an unqualified path |
| (None, self.parse_path(PathStyle::Expr)?) |
| }; |
| let hi = self.prev_token.span; |
| Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path))) |
| } else { |
| self.parse_literal_maybe_minus() |
| } |
| } |
| |
| /// Is this the start of a pattern beginning with a path? |
| fn is_start_of_pat_with_path(&mut self) -> bool { |
| self.check_path() |
| // Just for recovery (see `can_be_ident`). |
| || self.token.is_ident() && !self.token.is_bool_lit() && !self.token.is_keyword(kw::In) |
| } |
| |
| /// Would `parse_pat_ident` be appropriate here? |
| fn can_be_ident_pat(&mut self) -> bool { |
| self.check_ident() |
| && !self.token.is_bool_lit() // Avoid `true` or `false` as a binding as it is a literal. |
| && !self.token.is_path_segment_keyword() // Avoid e.g. `Self` as it is a path. |
| // Avoid `in`. Due to recovery in the list parser this messes with `for ( $pat in $expr )`. |
| && !self.token.is_keyword(kw::In) |
| // Try to do something more complex? |
| && self.look_ahead(1, |t| !matches!(t.kind, token::OpenDelim(Delimiter::Parenthesis) // A tuple struct pattern. |
| | token::OpenDelim(Delimiter::Brace) // A struct pattern. |
| | token::DotDotDot | token::DotDotEq | token::DotDot // A range pattern. |
| | token::ModSep // A tuple / struct variant pattern. |
| | token::Not)) // A macro expanding to a pattern. |
| } |
| |
| /// Parses `ident` or `ident @ pat`. |
| /// Used by the copy foo and ref foo patterns to give a good |
| /// error message when parsing mistakes like `ref foo(a, b)`. |
| fn parse_pat_ident(&mut self, binding_annotation: BindingAnnotation) -> PResult<'a, PatKind> { |
| let ident = self.parse_ident()?; |
| let sub = if self.eat(&token::At) { |
| Some(self.parse_pat_no_top_alt(Some("binding pattern"))?) |
| } else { |
| None |
| }; |
| |
| // Just to be friendly, if they write something like `ref Some(i)`, |
| // we end up here with `(` as the current token. |
| // This shortly leads to a parse error. Note that if there is no explicit |
| // binding mode then we do not end up here, because the lookahead |
| // will direct us over to `parse_enum_variant()`. |
| if self.token == token::OpenDelim(Delimiter::Parenthesis) { |
| return Err(self |
| .struct_span_err(self.prev_token.span, "expected identifier, found enum pattern")); |
| } |
| |
| Ok(PatKind::Ident(binding_annotation, ident, sub)) |
| } |
| |
| /// Parse a struct ("record") pattern (e.g. `Foo { ... }` or `Foo::Bar { ... }`). |
| fn parse_pat_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> { |
| if qself.is_some() { |
| // Feature gate the use of qualified paths in patterns |
| self.sess.gated_spans.gate(sym::more_qualified_paths, path.span); |
| } |
| self.bump(); |
| let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| { |
| e.span_label(path.span, "while parsing the fields for this pattern"); |
| e.emit(); |
| self.recover_stmt(); |
| (vec![], true) |
| }); |
| self.bump(); |
| Ok(PatKind::Struct(qself, path, fields, etc)) |
| } |
| |
| /// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`). |
| fn parse_pat_tuple_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> { |
| let (fields, _) = self.parse_paren_comma_seq(|p| { |
| p.parse_pat_allow_top_alt( |
| None, |
| RecoverComma::No, |
| RecoverColon::No, |
| CommaRecoveryMode::EitherTupleOrPipe, |
| ) |
| })?; |
| if qself.is_some() { |
| self.sess.gated_spans.gate(sym::more_qualified_paths, path.span); |
| } |
| Ok(PatKind::TupleStruct(qself, path, fields)) |
| } |
| |
| /// Are we sure this could not possibly be the start of a pattern? |
| /// |
| /// Currently, this only accounts for tokens that can follow identifiers |
| /// in patterns, but this can be extended as necessary. |
| fn isnt_pattern_start(&self) -> bool { |
| [ |
| token::Eq, |
| token::Colon, |
| token::Comma, |
| token::Semi, |
| token::At, |
| token::OpenDelim(Delimiter::Brace), |
| token::CloseDelim(Delimiter::Brace), |
| token::CloseDelim(Delimiter::Parenthesis), |
| ] |
| .contains(&self.token.kind) |
| } |
| |
| /// Parses `box pat` |
| fn parse_pat_box(&mut self) -> PResult<'a, PatKind> { |
| let box_span = self.prev_token.span; |
| |
| if self.isnt_pattern_start() { |
| self.struct_span_err( |
| self.token.span, |
| format!("expected pattern, found {}", super::token_descr(&self.token)), |
| ) |
| .span_note(box_span, "`box` is a reserved keyword") |
| .span_suggestion_verbose( |
| box_span.shrink_to_lo(), |
| "escape `box` to use it as an identifier", |
| "r#", |
| Applicability::MaybeIncorrect, |
| ) |
| .emit(); |
| |
| // We cannot use `parse_pat_ident()` since it will complain `box` |
| // is not an identifier. |
| let sub = if self.eat(&token::At) { |
| Some(self.parse_pat_no_top_alt(Some("binding pattern"))?) |
| } else { |
| None |
| }; |
| |
| Ok(PatKind::Ident(BindingAnnotation::NONE, Ident::new(kw::Box, box_span), sub)) |
| } else { |
| let pat = self.parse_pat_with_range_pat(false, None)?; |
| self.sess.gated_spans.gate(sym::box_patterns, box_span.to(self.prev_token.span)); |
| Ok(PatKind::Box(pat)) |
| } |
| } |
| |
| /// Parses the fields of a struct-like pattern. |
| fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<PatField>, bool)> { |
| let mut fields = Vec::new(); |
| let mut etc = false; |
| let mut ate_comma = true; |
| let mut delayed_err: Option<DiagnosticBuilder<'a, ErrorGuaranteed>> = None; |
| let mut etc_span = None; |
| |
| while self.token != token::CloseDelim(Delimiter::Brace) { |
| let attrs = match self.parse_outer_attributes() { |
| Ok(attrs) => attrs, |
| Err(err) => { |
| if let Some(mut delayed) = delayed_err { |
| delayed.emit(); |
| } |
| return Err(err); |
| } |
| }; |
| let lo = self.token.span; |
| |
| // check that a comma comes after every field |
| if !ate_comma { |
| let err = self.struct_span_err(self.token.span, "expected `,`"); |
| if let Some(mut delayed) = delayed_err { |
| delayed.emit(); |
| } |
| return Err(err); |
| } |
| ate_comma = false; |
| |
| if self.check(&token::DotDot) || self.token == token::DotDotDot { |
| etc = true; |
| let mut etc_sp = self.token.span; |
| |
| self.recover_one_fewer_dotdot(); |
| self.bump(); // `..` || `...` |
| |
| if self.token == token::CloseDelim(Delimiter::Brace) { |
| etc_span = Some(etc_sp); |
| break; |
| } |
| let token_str = super::token_descr(&self.token); |
| let msg = &format!("expected `}}`, found {}", token_str); |
| let mut err = self.struct_span_err(self.token.span, msg); |
| |
| err.span_label(self.token.span, "expected `}`"); |
| let mut comma_sp = None; |
| if self.token == token::Comma { |
| // Issue #49257 |
| let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span); |
| etc_sp = etc_sp.to(nw_span); |
| err.span_label( |
| etc_sp, |
| "`..` must be at the end and cannot have a trailing comma", |
| ); |
| comma_sp = Some(self.token.span); |
| self.bump(); |
| ate_comma = true; |
| } |
| |
| etc_span = Some(etc_sp.until(self.token.span)); |
| if self.token == token::CloseDelim(Delimiter::Brace) { |
| // If the struct looks otherwise well formed, recover and continue. |
| if let Some(sp) = comma_sp { |
| err.span_suggestion_short( |
| sp, |
| "remove this comma", |
| "", |
| Applicability::MachineApplicable, |
| ); |
| } |
| err.emit(); |
| break; |
| } else if self.token.is_ident() && ate_comma { |
| // Accept fields coming after `..,`. |
| // This way we avoid "pattern missing fields" errors afterwards. |
| // We delay this error until the end in order to have a span for a |
| // suggested fix. |
| if let Some(mut delayed_err) = delayed_err { |
| delayed_err.emit(); |
| return Err(err); |
| } else { |
| delayed_err = Some(err); |
| } |
| } else { |
| if let Some(mut err) = delayed_err { |
| err.emit(); |
| } |
| return Err(err); |
| } |
| } |
| |
| let field = |
| self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| { |
| let field = match this.parse_pat_field(lo, attrs) { |
| Ok(field) => Ok(field), |
| Err(err) => { |
| if let Some(mut delayed_err) = delayed_err.take() { |
| delayed_err.emit(); |
| } |
| return Err(err); |
| } |
| }?; |
| ate_comma = this.eat(&token::Comma); |
| // We just ate a comma, so there's no need to use |
| // `TrailingToken::Comma` |
| Ok((field, TrailingToken::None)) |
| })?; |
| |
| fields.push(field) |
| } |
| |
| if let Some(mut err) = delayed_err { |
| if let Some(etc_span) = etc_span { |
| err.multipart_suggestion( |
| "move the `..` to the end of the field list", |
| vec![ |
| (etc_span, String::new()), |
| (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })), |
| ], |
| Applicability::MachineApplicable, |
| ); |
| } |
| err.emit(); |
| } |
| Ok((fields, etc)) |
| } |
| |
| /// Recover on `...` as if it were `..` to avoid further errors. |
| /// See issue #46718. |
| fn recover_one_fewer_dotdot(&self) { |
| if self.token != token::DotDotDot { |
| return; |
| } |
| |
| self.struct_span_err(self.token.span, "expected field pattern, found `...`") |
| .span_suggestion( |
| self.token.span, |
| "to omit remaining fields, use one fewer `.`", |
| "..", |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| |
| fn parse_pat_field(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, PatField> { |
| // Check if a colon exists one ahead. This means we're parsing a fieldname. |
| let hi; |
| let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) { |
| // Parsing a pattern of the form `fieldname: pat`. |
| let fieldname = self.parse_field_name()?; |
| self.bump(); |
| let pat = self.parse_pat_allow_top_alt( |
| None, |
| RecoverComma::No, |
| RecoverColon::No, |
| CommaRecoveryMode::EitherTupleOrPipe, |
| )?; |
| hi = pat.span; |
| (pat, fieldname, false) |
| } else { |
| // Parsing a pattern of the form `(box) (ref) (mut) fieldname`. |
| let is_box = self.eat_keyword(kw::Box); |
| let boxed_span = self.token.span; |
| let is_ref = self.eat_keyword(kw::Ref); |
| let is_mut = self.eat_keyword(kw::Mut); |
| let fieldname = self.parse_field_name()?; |
| hi = self.prev_token.span; |
| |
| let mutability = match is_mut { |
| false => Mutability::Not, |
| true => Mutability::Mut, |
| }; |
| let ann = BindingAnnotation(ByRef::from(is_ref), mutability); |
| let fieldpat = self.mk_pat_ident(boxed_span.to(hi), ann, fieldname); |
| let subpat = |
| if is_box { self.mk_pat(lo.to(hi), PatKind::Box(fieldpat)) } else { fieldpat }; |
| (subpat, fieldname, true) |
| }; |
| |
| Ok(PatField { |
| ident: fieldname, |
| pat: subpat, |
| is_shorthand, |
| attrs, |
| id: ast::DUMMY_NODE_ID, |
| span: lo.to(hi), |
| is_placeholder: false, |
| }) |
| } |
| |
| pub(super) fn mk_pat_ident(&self, span: Span, ann: BindingAnnotation, ident: Ident) -> P<Pat> { |
| self.mk_pat(span, PatKind::Ident(ann, ident, None)) |
| } |
| |
| pub(super) fn mk_pat(&self, span: Span, kind: PatKind) -> P<Pat> { |
| P(Pat { kind, span, id: ast::DUMMY_NODE_ID, tokens: None }) |
| } |
| } |
