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use super::{ForceCollect, Parser, PathStyle, TrailingToken};
use crate::errors::{
self, AmbiguousRangePattern, DotDotDotForRemainingFields, DotDotDotRangeToPatternNotAllowed,
DotDotDotRestPattern, EnumPatternInsteadOfIdentifier, ExpectedBindingLeftOfAt,
ExpectedCommaAfterPatternField, GenericArgsInPatRequireTurbofishSyntax,
InclusiveRangeExtraEquals, InclusiveRangeMatchArrow, InclusiveRangeNoEnd, InvalidMutInPattern,
PatternOnWrongSideOfAt, RefMutOrderIncorrect, RemoveLet, RepeatedMutInPattern,
TopLevelOrPatternNotAllowed, TopLevelOrPatternNotAllowedSugg, TrailingVertNotAllowed,
UnexpectedLifetimeInPattern, UnexpectedVertVertBeforeFunctionParam,
UnexpectedVertVertInPattern,
};
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::{Applicability, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic, PResult};
use rustc_session::errors::ExprParenthesesNeeded;
use rustc_span::source_map::{respan, Span, Spanned};
use rustc_span::symbol::{kw, sym, Ident};
use thin_vec::{thin_vec, ThinVec};
#[derive(PartialEq, Copy, Clone)]
pub enum Expected {
ParameterName,
ArgumentName,
Identifier,
BindingPattern,
}
impl Expected {
// FIXME(#100717): migrate users of this to proper localization
fn to_string_or_fallback(expected: Option<Expected>) -> &'static str {
match expected {
Some(Expected::ParameterName) => "parameter name",
Some(Expected::ArgumentName) => "argument name",
Some(Expected::Identifier) => "identifier",
Some(Expected::BindingPattern) => "binding pattern",
None => "pattern",
}
}
}
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,
}
/// The syntax location of a given pattern. Used for diagnostics.
#[derive(Clone, Copy)]
pub enum PatternLocation {
LetBinding,
FunctionParameter,
}
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: Option<Expected>,
syntax_loc: Option<PatternLocation>,
) -> PResult<'a, P<Pat>> {
self.parse_pat_with_range_pat(true, expected, syntax_loc)
}
/// 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: Option<Expected>,
rc: RecoverComma,
ra: RecoverColon,
rt: CommaRecoveryMode,
) -> PResult<'a, P<Pat>> {
self.parse_pat_allow_top_alt_inner(expected, rc, ra, rt, None).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: Option<Expected>,
rc: RecoverComma,
ra: RecoverColon,
rt: CommaRecoveryMode,
syntax_loc: Option<PatternLocation>,
) -> 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, syntax_loc)?;
if rc == RecoverComma::Yes {
self.maybe_recover_unexpected_comma(
first_pat.span,
matches!(first_pat.kind, PatKind::MacCall(_)),
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(thin_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 = thin_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, syntax_loc).map_err(|mut err| {
err.span_label(lo, WHILE_PARSING_OR_MSG);
err
})?;
if rc == RecoverComma::Yes {
self.maybe_recover_unexpected_comma(pat.span, false, 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: Option<Expected>,
rc: RecoverComma,
syntax_loc: PatternLocation,
) -> 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,
Some(syntax_loc),
)?;
let colon = self.eat(&token::Colon);
if let PatKind::Or(pats) = &pat.kind {
let span = pat.span;
let pat = pprust::pat_to_string(&pat);
let sub = if pats.len() == 1 {
Some(TopLevelOrPatternNotAllowedSugg::RemoveLeadingVert { span, pat })
} else {
Some(TopLevelOrPatternNotAllowedSugg::WrapInParens { span, pat })
};
let mut err = self.sess.create_err(match syntax_loc {
PatternLocation::LetBinding => {
TopLevelOrPatternNotAllowed::LetBinding { span, sub }
}
PatternLocation::FunctionParameter => {
TopLevelOrPatternNotAllowed::FunctionParameter { span, sub }
}
});
if trailing_vert {
err.delay_as_bug();
}
err.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 {
self.sess.emit_err(UnexpectedVertVertBeforeFunctionParam { span: self.token.span });
self.bump();
}
self.parse_pat_before_ty(
Some(Expected::ParameterName),
RecoverComma::No,
PatternLocation::FunctionParameter,
)
}
/// 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.sess.emit_err(UnexpectedVertVertInPattern { span: self.token.span, start: 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) => {
// A `|` or possibly `||` token shouldn't be here. Ban it.
self.sess.emit_err(TrailingVertNotAllowed {
span: self.token.span,
start: lo,
token: self.token.clone(),
note_double_vert: matches!(self.token.kind, token::OrOr).then_some(()),
});
self.bump();
true
}
_ => false,
}
}
/// 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: Option<Expected>,
syntax_loc: Option<PatternLocation>,
) -> 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(syntax_loc)?
} 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), syntax_loc)?
} 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)
}
// Don't eagerly error on semantically invalid tokens when matching
// declarative macros, as the input to those doesn't have to be
// semantically valid. For attribute/derive proc macros this is not the
// case, so doing the recovery for them is fine.
} else if self.can_be_ident_pat()
|| (self.is_lit_bad_ident().is_some() && self.may_recover())
{
// 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, syntax_loc)?
} 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::Pat)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Pat)?)
};
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, Parser::mk_token_lit_char, |self_| {
let expected = Expected::to_string_or_fallback(expected);
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.sess.emit_err(DotDotDotRestPattern { span: lo });
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, None)?;
let whole_span = lhs.span.to(rhs.span);
if let PatKind::Ident(_, _, sub @ None) = &mut rhs.kind {
// The user inverted the order, so help them fix that.
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.sess.emit_err(PatternOnWrongSideOfAt {
whole_span,
whole_pat: pprust::pat_to_string(&rhs),
pattern: lhs_span,
binding: rhs.span,
});
} else {
// The special case above doesn't apply so we may have e.g. `A(x) @ B(y)`.
rhs.kind = PatKind::Wild;
self.sess.emit_err(ExpectedBindingLeftOfAt {
whole_span,
lhs: lhs.span,
rhs: rhs.span,
});
}
rhs.span = whole_span;
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.sess
.emit_err(AmbiguousRangePattern { span: pat.span, pat: pprust::pat_to_string(&pat) });
}
/// Parse `&pat` / `&mut pat`.
fn parse_pat_deref(&mut self, expected: Option<Expected>) -> PResult<'a, PatKind> {
self.expect_and()?;
if let token::Lifetime(name) = self.token.kind {
self.bump(); // `'a`
self.sess
.emit_err(UnexpectedLifetimeInPattern { span: self.prev_token.span, symbol: name });
}
let mutbl = self.parse_mutability();
let subpat = self.parse_pat_with_range_pat(false, expected, None)?;
Ok(PatKind::Ref(subpat, mutbl))
}
/// 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, syntax_loc: Option<PatternLocation>) -> PResult<'a, PatKind> {
let mut_span = self.prev_token.span;
if self.eat_keyword(kw::Ref) {
self.sess.emit_err(RefMutOrderIncorrect { span: mut_span.to(self.prev_token.span) });
return self.parse_pat_ident(BindingAnnotation::REF_MUT, syntax_loc);
}
self.recover_additional_muts();
// Make sure we don't allow e.g. `let mut $p;` where `$p:pat`.
if let token::Interpolated(nt) = &self.token.kind {
if let token::NtPat(_) = **nt {
self.expected_ident_found_err().emit();
}
}
// Parse the pattern we hope to be an identifier.
let mut pat = self.parse_pat_no_top_alt(Some(Expected::Identifier), None)?;
// 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)
}
/// 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 pat = pprust::pat_to_string(&pat);
self.sess.emit_err(if changed_any_binding {
InvalidMutInPattern::NestedIdent { span, pat }
} else {
InvalidMutInPattern::NonIdent { span, pat }
});
}
/// 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;
}
self.sess.emit_err(RepeatedMutInPattern { span: lo.to(self.prev_token.span) });
}
/// Parse macro invocation
fn parse_pat_mac_invoc(&mut self, path: Path) -> PResult<'a, PatKind> {
self.bump();
let args = self.parse_delim_args()?;
let mac = P(MacCall { path, args });
Ok(PatKind::MacCall(mac))
}
fn fatal_unexpected_non_pat(
&mut self,
err: DiagnosticBuilder<'a, ErrorGuaranteed>,
expected: Option<Expected>,
) -> PResult<'a, P<Pat>> {
err.cancel();
let expected = Expected::to_string_or_fallback(expected);
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();
}
None
};
Ok(PatKind::Range(Some(begin), end, re))
}
pub(super) fn inclusive_range_with_incorrect_end(&mut self) {
let tok = &self.token;
let span = self.prev_token.span;
// If the user typed "..==" instead of "..=", we want to give them
// a specific error message telling them to use "..=".
// If they typed "..=>", suggest they 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.
let no_space = tok.span.lo() == span.hi();
match tok.kind {
token::Eq if no_space => {
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.sess.emit_err(InclusiveRangeExtraEquals { span: span_with_eq });
}
token::Gt if no_space => {
let after_pat = span.with_hi(span.hi() - rustc_span::BytePos(1)).shrink_to_hi();
self.sess.emit_err(InclusiveRangeMatchArrow { span, arrow: tok.span, after_pat });
}
_ => {
self.sess.emit_err(InclusiveRangeNoEnd { span });
}
}
}
/// 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(syn @ RangeSyntax::DotDotDot) = &mut re.node {
*syn = RangeSyntax::DotDotEq;
self.sess.emit_err(DotDotDotRangeToPatternNotAllowed { span: re.span });
}
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::Pat)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Pat)?)
};
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,
syntax_loc: Option<PatternLocation>,
) -> PResult<'a, PatKind> {
let ident = self.parse_ident()?;
if self.may_recover()
&& !matches!(syntax_loc, Some(PatternLocation::FunctionParameter))
&& self.check_noexpect(&token::Lt)
&& self.look_ahead(1, |t| t.can_begin_type())
{
return Err(self.sess.create_err(GenericArgsInPatRequireTurbofishSyntax {
span: self.token.span,
suggest_turbofish: self.token.span.shrink_to_lo(),
}));
}
let sub = if self.eat(&token::At) {
Some(self.parse_pat_no_top_alt(Some(Expected::BindingPattern), None)?)
} 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(EnumPatternInsteadOfIdentifier { span: self.prev_token.span }
.into_diagnostic(&self.sess.span_diagnostic));
}
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<P<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();
(ThinVec::new(), 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<P<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() {
let descr = super::token_descr(&self.token);
self.sess.emit_err(errors::BoxNotPat {
span: self.token.span,
kw: box_span,
lo: box_span.shrink_to_lo(),
descr,
});
// 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(Expected::BindingPattern), None)?)
} 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, 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, (ThinVec<PatField>, bool)> {
let mut fields = ThinVec::new();
let mut etc = false;
let mut ate_comma = true;
let mut delayed_err: Option<DiagnosticBuilder<'a, ErrorGuaranteed>> = None;
let mut first_etc_and_maybe_comma_span = None;
let mut last_non_comma_dotdot_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 = ExpectedCommaAfterPatternField { span: self.token.span }
.into_diagnostic(&self.sess.span_diagnostic);
if let Some(mut delayed) = delayed_err {
delayed.emit();
}
return Err(err);
}
ate_comma = false;
if self.check(&token::DotDot)
|| self.check_noexpect(&token::DotDotDot)
|| self.check_keyword(kw::Underscore)
{
etc = true;
let mut etc_sp = self.token.span;
if first_etc_and_maybe_comma_span.is_none() {
if let Some(comma_tok) = self
.look_ahead(1, |t| if *t == token::Comma { Some(t.clone()) } else { None })
{
let nw_span = self
.sess
.source_map()
.span_extend_to_line(comma_tok.span)
.trim_start(comma_tok.span.shrink_to_lo())
.map(|s| self.sess.source_map().span_until_non_whitespace(s));
first_etc_and_maybe_comma_span = nw_span.map(|s| etc_sp.to(s));
} else {
first_etc_and_maybe_comma_span =
Some(self.sess.source_map().span_until_non_whitespace(etc_sp));
}
}
self.recover_bad_dot_dot();
self.bump(); // `..` || `...` || `_`
if self.token == token::CloseDelim(Delimiter::Brace) {
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;
}
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);
last_non_comma_dotdot_span = Some(this.prev_token.span);
// 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(first_etc_span) = first_etc_and_maybe_comma_span {
if self.prev_token == token::DotDot {
// We have `.., x, ..`.
err.multipart_suggestion(
"remove the starting `..`",
vec![(first_etc_span, String::new())],
Applicability::MachineApplicable,
);
} else {
if let Some(last_non_comma_dotdot_span) = last_non_comma_dotdot_span {
// We have `.., x`.
err.multipart_suggestion(
"move the `..` to the end of the field list",
vec![
(first_etc_span, String::new()),
(
self.token.span.to(last_non_comma_dotdot_span.shrink_to_hi()),
format!("{} .. }}", if ate_comma { "" } else { "," }),
),
],
Applicability::MachineApplicable,
);
}
}
}
err.emit();
}
Ok((fields, etc))
}
/// Recover on `...` or `_` as if it were `..` to avoid further errors.
/// See issue #46718.
fn recover_bad_dot_dot(&self) {
if self.token == token::DotDot {
return;
}
let token_str = pprust::token_to_string(&self.token);
self.sess.emit_err(DotDotDotForRemainingFields { span: self.token.span, token_str });
}
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 })
}
}