use super::{ForceCollect, Parser, PathStyle, TrailingToken}; use crate::parser::diagnostics::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_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` 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> { 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` is not used. /// /// Note that after the FCP in , /// 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> { 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, 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, 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, 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) -> 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) -> 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) { 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, 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> { 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 { // 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) -> PResult<'a, P> { 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) -> bool { struct AddMut(bool); impl MutVisitor for AddMut { fn visit_pat(&mut self, pat: &mut P) { 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> { 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) { self.sess.expr_parentheses_needed(&mut err, *sp); } Err(err) } /// Parses the range pattern end form `".." | "..." | "..=" ;`. fn parse_range_end(&mut self) -> Option> { 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, re: Spanned, ) -> 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) -> PResult<'a, PatKind> { let end = self.parse_pat_range_end()?; self.sess.gated_spans.gate(sym::half_open_range_patterns, re.span.to(self.prev_token.span)); 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() }) } fn parse_pat_range_end(&mut self) -> PResult<'a, P> { 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, 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, 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, bool)> { let mut fields = Vec::new(); let mut etc = false; let mut ate_comma = true; let mut delayed_err: Option> = 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 { self.mk_pat(span, PatKind::Ident(ann, ident, None)) } pub(super) fn mk_pat(&self, span: Span, kind: PatKind) -> P { P(Pat { kind, span, id: ast::DUMMY_NODE_ID, tokens: None }) } }