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fuchsia / third_party / rust / c38f75c21f016bffbf841ed5abce338f94201bde / . / compiler / rustc_parse / src / parser / diagnostics.rs
blob: f256dbf436021b55b9ab30f27b5200a5205020dd [file] [log] [blame]
use super::pat::Expected;
use super::{
BlockMode, CommaRecoveryMode, Parser, PathStyle, Restrictions, SemiColonMode, SeqSep,
TokenExpectType, TokenType,
};
use crate::errors::{
AmbiguousPlus, AsyncMoveBlockIn2015, AttributeOnParamType, BadQPathStage2, BadTypePlus,
BadTypePlusSub, ColonAsSemi, ComparisonOperatorsCannotBeChained,
ComparisonOperatorsCannotBeChainedSugg, ConstGenericWithoutBraces,
ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything, DocCommentOnParamType,
DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
GenericParamsWithoutAngleBrackets, GenericParamsWithoutAngleBracketsSugg,
HelpIdentifierStartsWithNumber, HelpUseLatestEdition, InInTypo, IncorrectAwait,
IncorrectSemicolon, IncorrectUseOfAwait, PatternMethodParamWithoutBody, QuestionMarkInType,
QuestionMarkInTypeSugg, SelfParamNotFirst, StructLiteralBodyWithoutPath,
StructLiteralBodyWithoutPathSugg, StructLiteralNeedingParens, StructLiteralNeedingParensSugg,
SuggAddMissingLetStmt, SuggEscapeIdentifier, SuggRemoveComma, TernaryOperator,
UnexpectedConstInGenericParam, UnexpectedConstParamDeclaration,
UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets, UseEqInstead, WrapType,
};
use crate::fluent_generated as fluent;
use crate::parser;
use crate::parser::attr::InnerAttrPolicy;
use ast::token::IdentIsRaw;
use parser::Recovered;
use rustc_ast as ast;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, Delimiter, Lit, LitKind, Token, TokenKind};
use rustc_ast::tokenstream::AttrTokenTree;
use rustc_ast::util::parser::AssocOp;
use rustc_ast::{
AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingMode, Block,
BlockCheckMode, Expr, ExprKind, GenericArg, Generics, HasTokens, Item, ItemKind, Param, Pat,
PatKind, Path, PathSegment, QSelf, Ty, TyKind,
};
use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{
pluralize, Applicability, Diag, DiagCtxt, ErrorGuaranteed, FatalError, PErr, PResult,
Subdiagnostic,
};
use rustc_session::errors::ExprParenthesesNeeded;
use rustc_span::source_map::Spanned;
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::{BytePos, Span, SpanSnippetError, Symbol, DUMMY_SP};
use std::mem::take;
use std::ops::{Deref, DerefMut};
use thin_vec::{thin_vec, ThinVec};
/// Creates a placeholder argument.
pub(super) fn dummy_arg(ident: Ident, guar: ErrorGuaranteed) -> Param {
let pat = P(Pat {
id: ast::DUMMY_NODE_ID,
kind: PatKind::Ident(BindingMode::NONE, ident, None),
span: ident.span,
tokens: None,
});
let ty = Ty { kind: TyKind::Err(guar), span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
Param {
attrs: AttrVec::default(),
id: ast::DUMMY_NODE_ID,
pat,
span: ident.span,
ty: P(ty),
is_placeholder: false,
}
}
pub(super) trait RecoverQPath: Sized + 'static {
const PATH_STYLE: PathStyle = PathStyle::Expr;
fn to_ty(&self) -> Option<P<Ty>>;
fn recovered(qself: Option<P<QSelf>>, path: ast::Path) -> Self;
}
impl RecoverQPath for Ty {
const PATH_STYLE: PathStyle = PathStyle::Type;
fn to_ty(&self) -> Option<P<Ty>> {
Some(P(self.clone()))
}
fn recovered(qself: Option<P<QSelf>>, path: ast::Path) -> Self {
Self {
span: path.span,
kind: TyKind::Path(qself, path),
id: ast::DUMMY_NODE_ID,
tokens: None,
}
}
}
impl RecoverQPath for Pat {
const PATH_STYLE: PathStyle = PathStyle::Pat;
fn to_ty(&self) -> Option<P<Ty>> {
self.to_ty()
}
fn recovered(qself: Option<P<QSelf>>, path: ast::Path) -> Self {
Self {
span: path.span,
kind: PatKind::Path(qself, path),
id: ast::DUMMY_NODE_ID,
tokens: None,
}
}
}
impl RecoverQPath for Expr {
fn to_ty(&self) -> Option<P<Ty>> {
self.to_ty()
}
fn recovered(qself: Option<P<QSelf>>, path: ast::Path) -> Self {
Self {
span: path.span,
kind: ExprKind::Path(qself, path),
attrs: AttrVec::new(),
id: ast::DUMMY_NODE_ID,
tokens: None,
}
}
}
/// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
pub(crate) enum ConsumeClosingDelim {
Yes,
No,
}
#[derive(Clone, Copy)]
pub enum AttemptLocalParseRecovery {
Yes,
No,
}
impl AttemptLocalParseRecovery {
pub fn yes(&self) -> bool {
match self {
AttemptLocalParseRecovery::Yes => true,
AttemptLocalParseRecovery::No => false,
}
}
pub fn no(&self) -> bool {
match self {
AttemptLocalParseRecovery::Yes => false,
AttemptLocalParseRecovery::No => true,
}
}
}
/// Information for emitting suggestions and recovering from
/// C-style `i++`, `--i`, etc.
#[derive(Debug, Copy, Clone)]
struct IncDecRecovery {
/// Is this increment/decrement its own statement?
standalone: IsStandalone,
/// Is this an increment or decrement?
op: IncOrDec,
/// Is this pre- or postfix?
fixity: UnaryFixity,
}
/// Is an increment or decrement expression its own statement?
#[derive(Debug, Copy, Clone)]
enum IsStandalone {
/// It's standalone, i.e., its own statement.
Standalone,
/// It's a subexpression, i.e., *not* standalone.
Subexpr,
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum IncOrDec {
Inc,
Dec,
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum UnaryFixity {
Pre,
Post,
}
impl IncOrDec {
fn chr(&self) -> char {
match self {
Self::Inc => '+',
Self::Dec => '-',
}
}
fn name(&self) -> &'static str {
match self {
Self::Inc => "increment",
Self::Dec => "decrement",
}
}
}
impl std::fmt::Display for UnaryFixity {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Self::Pre => write!(f, "prefix"),
Self::Post => write!(f, "postfix"),
}
}
}
struct MultiSugg {
msg: String,
patches: Vec<(Span, String)>,
applicability: Applicability,
}
impl MultiSugg {
fn emit(self, err: &mut Diag<'_>) {
err.multipart_suggestion(self.msg, self.patches, self.applicability);
}
fn emit_verbose(self, err: &mut Diag<'_>) {
err.multipart_suggestion_verbose(self.msg, self.patches, self.applicability);
}
}
/// SnapshotParser is used to create a snapshot of the parser
/// without causing duplicate errors being emitted when the `Parser`
/// is dropped.
pub struct SnapshotParser<'a> {
parser: Parser<'a>,
}
impl<'a> Deref for SnapshotParser<'a> {
type Target = Parser<'a>;
fn deref(&self) -> &Self::Target {
&self.parser
}
}
impl<'a> DerefMut for SnapshotParser<'a> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.parser
}
}
impl<'a> Parser<'a> {
pub fn dcx(&self) -> &'a DiagCtxt {
&self.psess.dcx
}
/// Replace `self` with `snapshot.parser`.
pub(super) fn restore_snapshot(&mut self, snapshot: SnapshotParser<'a>) {
*self = snapshot.parser;
}
/// Create a snapshot of the `Parser`.
pub fn create_snapshot_for_diagnostic(&self) -> SnapshotParser<'a> {
let snapshot = self.clone();
SnapshotParser { parser: snapshot }
}
pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
self.psess.source_map().span_to_snippet(span)
}
/// Emits an error with suggestions if an identifier was expected but not found.
///
/// Returns a possibly recovered identifier.
pub(super) fn expected_ident_found(
&mut self,
recover: bool,
) -> PResult<'a, (Ident, IdentIsRaw)> {
if let TokenKind::DocComment(..) = self.prev_token.kind {
return Err(self.dcx().create_err(DocCommentDoesNotDocumentAnything {
span: self.prev_token.span,
missing_comma: None,
}));
}
let valid_follow = &[
TokenKind::Eq,
TokenKind::Colon,
TokenKind::Comma,
TokenKind::Semi,
TokenKind::PathSep,
TokenKind::OpenDelim(Delimiter::Brace),
TokenKind::OpenDelim(Delimiter::Parenthesis),
TokenKind::CloseDelim(Delimiter::Brace),
TokenKind::CloseDelim(Delimiter::Parenthesis),
];
let mut recovered_ident = None;
// we take this here so that the correct original token is retained in
// the diagnostic, regardless of eager recovery.
let bad_token = self.token.clone();
// suggest prepending a keyword in identifier position with `r#`
let suggest_raw = if let Some((ident, IdentIsRaw::No)) = self.token.ident()
&& ident.is_raw_guess()
&& self.look_ahead(1, |t| valid_follow.contains(&t.kind))
{
recovered_ident = Some((ident, IdentIsRaw::Yes));
// `Symbol::to_string()` is different from `Symbol::into_diag_arg()`,
// which uses `Symbol::to_ident_string()` and "helpfully" adds an implicit `r#`
let ident_name = ident.name.to_string();
Some(SuggEscapeIdentifier { span: ident.span.shrink_to_lo(), ident_name })
} else {
None
};
let suggest_remove_comma =
if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
if recover {
self.bump();
recovered_ident = self.ident_or_err(false).ok();
};
Some(SuggRemoveComma { span: bad_token.span })
} else {
None
};
let help_cannot_start_number = self.is_lit_bad_ident().map(|(len, valid_portion)| {
let (invalid, valid) = self.token.span.split_at(len as u32);
recovered_ident = Some((Ident::new(valid_portion, valid), IdentIsRaw::No));
HelpIdentifierStartsWithNumber { num_span: invalid }
});
let err = ExpectedIdentifier {
span: bad_token.span,
token: bad_token,
suggest_raw,
suggest_remove_comma,
help_cannot_start_number,
};
let mut err = self.dcx().create_err(err);
// if the token we have is a `<`
// it *might* be a misplaced generic
// FIXME: could we recover with this?
if self.token == token::Lt {
// all keywords that could have generic applied
let valid_prev_keywords =
[kw::Fn, kw::Type, kw::Struct, kw::Enum, kw::Union, kw::Trait];
// If we've expected an identifier,
// and the current token is a '<'
// if the previous token is a valid keyword
// that might use a generic, then suggest a correct
// generic placement (later on)
let maybe_keyword = self.prev_token.clone();
if valid_prev_keywords.into_iter().any(|x| maybe_keyword.is_keyword(x)) {
// if we have a valid keyword, attempt to parse generics
// also obtain the keywords symbol
match self.parse_generics() {
Ok(generic) => {
if let TokenKind::Ident(symbol, _) = maybe_keyword.kind {
let ident_name = symbol;
// at this point, we've found something like
// `fn <T>id`
// and current token should be Ident with the item name (i.e. the function name)
// if there is a `<` after the fn name, then don't show a suggestion, show help
if !self.look_ahead(1, |t| *t == token::Lt)
&& let Ok(snippet) =
self.psess.source_map().span_to_snippet(generic.span)
{
err.multipart_suggestion_verbose(
format!("place the generic parameter name after the {ident_name} name"),
vec![
(self.token.span.shrink_to_hi(), snippet),
(generic.span, String::new())
],
Applicability::MaybeIncorrect,
);
} else {
err.help(format!(
"place the generic parameter name after the {ident_name} name"
));
}
}
}
Err(err) => {
// if there's an error parsing the generics,
// then don't do a misplaced generics suggestion
// and emit the expected ident error instead;
err.cancel();
}
}
}
}
if let Some(recovered_ident) = recovered_ident
&& recover
{
err.emit();
Ok(recovered_ident)
} else {
Err(err)
}
}
pub(super) fn expected_ident_found_err(&mut self) -> Diag<'a> {
self.expected_ident_found(false).unwrap_err()
}
/// Checks if the current token is a integer or float literal and looks like
/// it could be a invalid identifier with digits at the start.
///
/// Returns the number of characters (bytes) composing the invalid portion
/// of the identifier and the valid portion of the identifier.
pub(super) fn is_lit_bad_ident(&mut self) -> Option<(usize, Symbol)> {
// ensure that the integer literal is followed by a *invalid*
// suffix: this is how we know that it is a identifier with an
// invalid beginning.
if let token::Literal(Lit {
kind: token::LitKind::Integer | token::LitKind::Float,
symbol,
suffix: Some(suffix), // no suffix makes it a valid literal
}) = self.token.kind
&& rustc_ast::MetaItemLit::from_token(&self.token).is_none()
{
Some((symbol.as_str().len(), suffix))
} else {
None
}
}
pub(super) fn expected_one_of_not_found(
&mut self,
edible: &[TokenKind],
inedible: &[TokenKind],
) -> PResult<'a, Recovered> {
debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
fn tokens_to_string(tokens: &[TokenType]) -> String {
let mut i = tokens.iter();
// This might be a sign we need a connect method on `Iterator`.
let b = i.next().map_or_else(String::new, |t| t.to_string());
i.enumerate().fold(b, |mut b, (i, a)| {
if tokens.len() > 2 && i == tokens.len() - 2 {
b.push_str(", or ");
} else if tokens.len() == 2 && i == tokens.len() - 2 {
b.push_str(" or ");
} else {
b.push_str(", ");
}
b.push_str(&a.to_string());
b
})
}
self.expected_tokens.extend(edible.iter().chain(inedible).cloned().map(TokenType::Token));
let mut expected = self
.expected_tokens
.iter()
.filter(|token| {
// Filter out suggestions that suggest the same token which was found and deemed incorrect.
fn is_ident_eq_keyword(found: &TokenKind, expected: &TokenType) -> bool {
if let TokenKind::Ident(current_sym, _) = found
&& let TokenType::Keyword(suggested_sym) = expected
{
return current_sym == suggested_sym;
}
false
}
if **token != parser::TokenType::Token(self.token.kind.clone()) {
let eq = is_ident_eq_keyword(&self.token.kind, &token);
// If the suggestion is a keyword and the found token is an ident,
// the content of which are equal to the suggestion's content,
// we can remove that suggestion (see the `return false` below).
// If this isn't the case however, and the suggestion is a token the
// content of which is the same as the found token's, we remove it as well.
if !eq {
if let TokenType::Token(kind) = &token {
if kind == &self.token.kind {
return false;
}
}
return true;
}
}
false
})
.cloned()
.collect::<Vec<_>>();
expected.sort_by_cached_key(|x| x.to_string());
expected.dedup();
let sm = self.psess.source_map();
// Special-case "expected `;`" errors.
if expected.contains(&TokenType::Token(token::Semi)) {
// If the user is trying to write a ternary expression, recover it and
// return an Err to prevent a cascade of irrelevant diagnostics.
if self.prev_token == token::Question
&& let Err(e) = self.maybe_recover_from_ternary_operator()
{
return Err(e);
}
if self.token.span == DUMMY_SP || self.prev_token.span == DUMMY_SP {
// Likely inside a macro, can't provide meaningful suggestions.
} else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) {
// The current token is in the same line as the prior token, not recoverable.
} else if [token::Comma, token::Colon].contains(&self.token.kind)
&& self.prev_token.kind == token::CloseDelim(Delimiter::Parenthesis)
{
// Likely typo: The current token is on a new line and is expected to be
// `.`, `;`, `?`, or an operator after a close delimiter token.
//
// let a = std::process::Command::new("echo")
// .arg("1")
// ,arg("2")
// ^
// https://github.com/rust-lang/rust/issues/72253
} else if self.look_ahead(1, |t| {
t == &token::CloseDelim(Delimiter::Brace)
|| t.can_begin_expr() && t.kind != token::Colon
}) && [token::Comma, token::Colon].contains(&self.token.kind)
{
// Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
// either `,` or `:`, and the next token could either start a new statement or is a
// block close. For example:
//
// let x = 32:
// let y = 42;
self.dcx().emit_err(ExpectedSemi {
span: self.token.span,
token: self.token.clone(),
unexpected_token_label: None,
sugg: ExpectedSemiSugg::ChangeToSemi(self.token.span),
});
self.bump();
return Ok(Recovered::Yes);
} else if self.look_ahead(0, |t| {
t == &token::CloseDelim(Delimiter::Brace)
|| ((t.can_begin_expr() || t.can_begin_item())
&& t != &token::Semi
&& t != &token::Pound)
// Avoid triggering with too many trailing `#` in raw string.
|| (sm.is_multiline(
self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
) && t == &token::Pound)
}) && !expected.contains(&TokenType::Token(token::Comma))
{
// Missing semicolon typo. This is triggered if the next token could either start a
// new statement or is a block close. For example:
//
// let x = 32
// let y = 42;
let span = self.prev_token.span.shrink_to_hi();
self.dcx().emit_err(ExpectedSemi {
span,
token: self.token.clone(),
unexpected_token_label: Some(self.token.span),
sugg: ExpectedSemiSugg::AddSemi(span),
});
return Ok(Recovered::Yes);
}
}
if self.token.kind == TokenKind::EqEq
&& self.prev_token.is_ident()
&& expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Eq)))
{
// Likely typo: `=` → `==` in let expr or enum item
return Err(self.dcx().create_err(UseEqInstead { span: self.token.span }));
}
if self.token.is_keyword(kw::Move) && self.prev_token.is_keyword(kw::Async) {
// The 2015 edition is in use because parsing of `async move` has failed.
let span = self.prev_token.span.to(self.token.span);
return Err(self.dcx().create_err(AsyncMoveBlockIn2015 { span }));
}
let expect = tokens_to_string(&expected);
let actual = super::token_descr(&self.token);
let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
let fmt = format!("expected one of {expect}, found {actual}");
let short_expect = if expected.len() > 6 {
format!("{} possible tokens", expected.len())
} else {
expect
};
(fmt, (self.prev_token.span.shrink_to_hi(), format!("expected one of {short_expect}")))
} else if expected.is_empty() {
(
format!("unexpected token: {actual}"),
(self.prev_token.span, "unexpected token after this".to_string()),
)
} else {
(
format!("expected {expect}, found {actual}"),
(self.prev_token.span.shrink_to_hi(), format!("expected {expect}")),
)
};
self.last_unexpected_token_span = Some(self.token.span);
// FIXME: translation requires list formatting (for `expect`)
let mut err = self.dcx().struct_span_err(self.token.span, msg_exp);
// Look for usages of '=>' where '>=' was probably intended
if self.token == token::FatArrow
&& expected
.iter()
.any(|tok| matches!(tok, TokenType::Operator | TokenType::Token(TokenKind::Le)))
&& !expected.iter().any(|tok| {
matches!(
tok,
TokenType::Token(TokenKind::FatArrow) | TokenType::Token(TokenKind::Comma)
)
})
{
err.span_suggestion(
self.token.span,
"you might have meant to write a \"greater than or equal to\" comparison",
">=",
Applicability::MaybeIncorrect,
);
}
if let TokenKind::Ident(symbol, _) = &self.prev_token.kind {
if ["def", "fun", "func", "function"].contains(&symbol.as_str()) {
err.span_suggestion_short(
self.prev_token.span,
format!("write `fn` instead of `{symbol}` to declare a function"),
"fn",
Applicability::MachineApplicable,
);
}
}
if let TokenKind::Ident(prev, _) = &self.prev_token.kind
&& let TokenKind::Ident(cur, _) = &self.token.kind
{
let concat = Symbol::intern(&format!("{prev}{cur}"));
let ident = Ident::new(concat, DUMMY_SP);
if ident.is_used_keyword() || ident.is_reserved() || ident.is_raw_guess() {
let span = self.prev_token.span.to(self.token.span);
err.span_suggestion_verbose(
span,
format!("consider removing the space to spell keyword `{concat}`"),
concat,
Applicability::MachineApplicable,
);
}
}
// Try to detect an intended c-string literal while using a pre-2021 edition. The heuristic
// here is to identify a cooked, uninterpolated `c` id immediately followed by a string, or
// a cooked, uninterpolated `cr` id immediately followed by a string or a `#`, in an edition
// where c-string literals are not allowed. There is the very slight possibility of a false
// positive for a `cr#` that wasn't intended to start a c-string literal, but identifying
// that in the parser requires unbounded lookahead, so we only add a hint to the existing
// error rather than replacing it entirely.
if ((self.prev_token.kind == TokenKind::Ident(sym::c, IdentIsRaw::No)
&& matches!(&self.token.kind, TokenKind::Literal(token::Lit { kind: token::Str, .. })))
|| (self.prev_token.kind == TokenKind::Ident(sym::cr, IdentIsRaw::No)
&& matches!(
&self.token.kind,
TokenKind::Literal(token::Lit { kind: token::Str, .. }) | token::Pound
)))
&& self.prev_token.span.hi() == self.token.span.lo()
&& !self.token.span.at_least_rust_2021()
{
err.note("you may be trying to write a c-string literal");
err.note("c-string literals require Rust 2021 or later");
err.subdiagnostic(self.dcx(), HelpUseLatestEdition::new());
}
// `pub` may be used for an item or `pub(crate)`
if self.prev_token.is_ident_named(sym::public)
&& (self.token.can_begin_item()
|| self.token.kind == TokenKind::OpenDelim(Delimiter::Parenthesis))
{
err.span_suggestion_short(
self.prev_token.span,
"write `pub` instead of `public` to make the item public",
"pub",
Applicability::MachineApplicable,
);
}
if let token::DocComment(kind, style, _) = self.token.kind {
// We have something like `expr //!val` where the user likely meant `expr // !val`
let pos = self.token.span.lo() + BytePos(2);
let span = self.token.span.with_lo(pos).with_hi(pos);
err.span_suggestion_verbose(
span,
format!(
"add a space before {} to write a regular comment",
match (kind, style) {
(token::CommentKind::Line, ast::AttrStyle::Inner) => "`!`",
(token::CommentKind::Block, ast::AttrStyle::Inner) => "`!`",
(token::CommentKind::Line, ast::AttrStyle::Outer) => "the last `/`",
(token::CommentKind::Block, ast::AttrStyle::Outer) => "the last `*`",
},
),
" ".to_string(),
Applicability::MachineApplicable,
);
}
let sp = if self.token == token::Eof {
// This is EOF; don't want to point at the following char, but rather the last token.
self.prev_token.span
} else {
label_sp
};
if self.check_too_many_raw_str_terminators(&mut err) {
if expected.contains(&TokenType::Token(token::Semi)) && self.eat(&token::Semi) {
err.emit();
return Ok(Recovered::Yes);
} else {
return Err(err);
}
}
if self.prev_token.span == DUMMY_SP {
// Account for macro context where the previous span might not be
// available to avoid incorrect output (#54841).
err.span_label(self.token.span, label_exp);
} else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
// When the spans are in the same line, it means that the only content between
// them is whitespace, point at the found token in that case:
//
// X | () => { syntax error };
// | ^^^^^ expected one of 8 possible tokens here
//
// instead of having:
//
// X | () => { syntax error };
// | -^^^^^ unexpected token
// | |
// | expected one of 8 possible tokens here
err.span_label(self.token.span, label_exp);
} else {
err.span_label(sp, label_exp);
err.span_label(self.token.span, "unexpected token");
}
Err(err)
}
/// The user has written `#[attr] expr` which is unsupported. (#106020)
pub(super) fn attr_on_non_tail_expr(&self, expr: &Expr) -> ErrorGuaranteed {
// Missing semicolon typo error.
let span = self.prev_token.span.shrink_to_hi();
let mut err = self.dcx().create_err(ExpectedSemi {
span,
token: self.token.clone(),
unexpected_token_label: Some(self.token.span),
sugg: ExpectedSemiSugg::AddSemi(span),
});
let attr_span = match &expr.attrs[..] {
[] => unreachable!(),
[only] => only.span,
[first, rest @ ..] => {
for attr in rest {
err.span_label(attr.span, "");
}
first.span
}
};
err.span_label(
attr_span,
format!(
"only `;` terminated statements or tail expressions are allowed after {}",
if expr.attrs.len() == 1 { "this attribute" } else { "these attributes" },
),
);
if self.token == token::Pound
&& self.look_ahead(1, |t| t.kind == token::OpenDelim(Delimiter::Bracket))
{
// We have
// #[attr]
// expr
// #[not_attr]
// other_expr
err.span_label(span, "expected `;` here");
err.multipart_suggestion(
"alternatively, consider surrounding the expression with a block",
vec![
(expr.span.shrink_to_lo(), "{ ".to_string()),
(expr.span.shrink_to_hi(), " }".to_string()),
],
Applicability::MachineApplicable,
);
// Special handling for `#[cfg(...)]` chains
let mut snapshot = self.create_snapshot_for_diagnostic();
if let [attr] = &expr.attrs[..]
&& let ast::AttrKind::Normal(attr_kind) = &attr.kind
&& let [segment] = &attr_kind.item.path.segments[..]
&& segment.ident.name == sym::cfg
&& let Some(args_span) = attr_kind.item.args.span()
&& let next_attr = match snapshot.parse_attribute(InnerAttrPolicy::Forbidden(None))
{
Ok(next_attr) => next_attr,
Err(inner_err) => {
inner_err.cancel();
return err.emit();
}
}
&& let ast::AttrKind::Normal(next_attr_kind) = next_attr.kind
&& let Some(next_attr_args_span) = next_attr_kind.item.args.span()
&& let [next_segment] = &next_attr_kind.item.path.segments[..]
&& segment.ident.name == sym::cfg
{
let next_expr = match snapshot.parse_expr() {
Ok(next_expr) => next_expr,
Err(inner_err) => {
inner_err.cancel();
return err.emit();
}
};
// We have for sure
// #[cfg(..)]
// expr
// #[cfg(..)]
// other_expr
// So we suggest using `if cfg!(..) { expr } else if cfg!(..) { other_expr }`.
let margin = self.psess.source_map().span_to_margin(next_expr.span).unwrap_or(0);
let sugg = vec![
(attr.span.with_hi(segment.span().hi()), "if cfg!".to_string()),
(args_span.shrink_to_hi().with_hi(attr.span.hi()), " {".to_string()),
(expr.span.shrink_to_lo(), " ".to_string()),
(
next_attr.span.with_hi(next_segment.span().hi()),
"} else if cfg!".to_string(),
),
(
next_attr_args_span.shrink_to_hi().with_hi(next_attr.span.hi()),
" {".to_string(),
),
(next_expr.span.shrink_to_lo(), " ".to_string()),
(next_expr.span.shrink_to_hi(), format!("\n{}}}", " ".repeat(margin))),
];
err.multipart_suggestion(
"it seems like you are trying to provide different expressions depending on \
`cfg`, consider using `if cfg!(..)`",
sugg,
Applicability::MachineApplicable,
);
}
}
err.emit()
}
fn check_too_many_raw_str_terminators(&mut self, err: &mut Diag<'_>) -> bool {
let sm = self.psess.source_map();
match (&self.prev_token.kind, &self.token.kind) {
(
TokenKind::Literal(Lit {
kind: LitKind::StrRaw(n_hashes) | LitKind::ByteStrRaw(n_hashes),
..
}),
TokenKind::Pound,
) if !sm.is_multiline(
self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
) =>
{
let n_hashes: u8 = *n_hashes;
err.primary_message("too many `#` when terminating raw string");
let str_span = self.prev_token.span;
let mut span = self.token.span;
let mut count = 0;
while self.token.kind == TokenKind::Pound
&& !sm.is_multiline(span.shrink_to_hi().until(self.token.span.shrink_to_lo()))
{
span = span.with_hi(self.token.span.hi());
self.bump();
count += 1;
}
err.span(span);
err.span_suggestion(
span,
format!("remove the extra `#`{}", pluralize!(count)),
"",
Applicability::MachineApplicable,
);
err.span_label(
str_span,
format!("this raw string started with {n_hashes} `#`{}", pluralize!(n_hashes)),
);
true
}
_ => false,
}
}
pub fn maybe_suggest_struct_literal(
&mut self,
lo: Span,
s: BlockCheckMode,
maybe_struct_name: token::Token,
can_be_struct_literal: bool,
) -> Option<PResult<'a, P<Block>>> {
if self.token.is_ident() && self.look_ahead(1, |t| t == &token::Colon) {
// We might be having a struct literal where people forgot to include the path:
// fn foo() -> Foo {
// field: value,
// }
debug!(?maybe_struct_name, ?self.token);
let mut snapshot = self.create_snapshot_for_diagnostic();
let path = Path {
segments: ThinVec::new(),
span: self.prev_token.span.shrink_to_lo(),
tokens: None,
};
let struct_expr = snapshot.parse_expr_struct(None, path, false);
let block_tail = self.parse_block_tail(lo, s, AttemptLocalParseRecovery::No);
return Some(match (struct_expr, block_tail) {
(Ok(expr), Err(err)) => {
// We have encountered the following:
// fn foo() -> Foo {
// field: value,
// }
// Suggest:
// fn foo() -> Foo { Path {
// field: value,
// } }
let guar = err.delay_as_bug();
self.restore_snapshot(snapshot);
let mut tail = self.mk_block(
thin_vec![self.mk_stmt_err(expr.span, guar)],
s,
lo.to(self.prev_token.span),
);
tail.could_be_bare_literal = true;
if maybe_struct_name.is_ident() && can_be_struct_literal {
// Account for `if Example { a: one(), }.is_pos() {}`.
// expand `before` so that we take care of module path such as:
// `foo::Bar { ... } `
// we expect to suggest `(foo::Bar { ... })` instead of `foo::(Bar { ... })`
let sm = self.psess.source_map();
let before = maybe_struct_name.span.shrink_to_lo();
if let Ok(extend_before) = sm.span_extend_prev_while(before, |t| {
t.is_alphanumeric() || t == ':' || t == '_'
}) {
Err(self.dcx().create_err(StructLiteralNeedingParens {
span: maybe_struct_name.span.to(expr.span),
sugg: StructLiteralNeedingParensSugg {
before: extend_before.shrink_to_lo(),
after: expr.span.shrink_to_hi(),
},
}))
} else {
return None;
}
} else {
self.dcx().emit_err(StructLiteralBodyWithoutPath {
span: expr.span,
sugg: StructLiteralBodyWithoutPathSugg {
before: expr.span.shrink_to_lo(),
after: expr.span.shrink_to_hi(),
},
});
Ok(tail)
}
}
(Err(err), Ok(tail)) => {
// We have a block tail that contains a somehow valid type ascription expr.
err.cancel();
Ok(tail)
}
(Err(snapshot_err), Err(err)) => {
// We don't know what went wrong, emit the normal error.
snapshot_err.cancel();
self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
Err(err)
}
(Ok(_), Ok(mut tail)) => {
tail.could_be_bare_literal = true;
Ok(tail)
}
});
}
None
}
pub(super) fn recover_closure_body(
&mut self,
mut err: Diag<'a>,
before: token::Token,
prev: token::Token,
token: token::Token,
lo: Span,
decl_hi: Span,
) -> PResult<'a, P<Expr>> {
err.span_label(lo.to(decl_hi), "while parsing the body of this closure");
let guar = match before.kind {
token::OpenDelim(Delimiter::Brace)
if !matches!(token.kind, token::OpenDelim(Delimiter::Brace)) =>
{
// `{ || () }` should have been `|| { () }`
err.multipart_suggestion(
"you might have meant to open the body of the closure, instead of enclosing \
the closure in a block",
vec![
(before.span, String::new()),
(prev.span.shrink_to_hi(), " {".to_string()),
],
Applicability::MaybeIncorrect,
);
let guar = err.emit();
self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Brace)]);
guar
}
token::OpenDelim(Delimiter::Parenthesis)
if !matches!(token.kind, token::OpenDelim(Delimiter::Brace)) =>
{
// We are within a function call or tuple, we can emit the error
// and recover.
self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Parenthesis), &token::Comma]);
err.multipart_suggestion_verbose(
"you might have meant to open the body of the closure",
vec![
(prev.span.shrink_to_hi(), " {".to_string()),
(self.token.span.shrink_to_lo(), "}".to_string()),
],
Applicability::MaybeIncorrect,
);
err.emit()
}
_ if !matches!(token.kind, token::OpenDelim(Delimiter::Brace)) => {
// We don't have a heuristic to correctly identify where the block
// should be closed.
err.multipart_suggestion_verbose(
"you might have meant to open the body of the closure",
vec![(prev.span.shrink_to_hi(), " {".to_string())],
Applicability::HasPlaceholders,
);
return Err(err);
}
_ => return Err(err),
};
Ok(self.mk_expr_err(lo.to(self.token.span), guar))
}
/// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
/// passes through any errors encountered. Used for error recovery.
pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
if let Err(err) =
self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
Ok(p.parse_token_tree())
})
{
err.cancel();
}
}
/// This function checks if there are trailing angle brackets and produces
/// a diagnostic to suggest removing them.
///
/// ```ignore (diagnostic)
/// let _ = [1, 2, 3].into_iter().collect::<Vec<usize>>>>();
/// ^^ help: remove extra angle brackets
/// ```
///
/// If `true` is returned, then trailing brackets were recovered, tokens were consumed
/// up until one of the tokens in 'end' was encountered, and an error was emitted.
pub(super) fn check_trailing_angle_brackets(
&mut self,
segment: &PathSegment,
end: &[&TokenKind],
) -> Option<ErrorGuaranteed> {
if !self.may_recover() {
return None;
}
// This function is intended to be invoked after parsing a path segment where there are two
// cases:
//
// 1. A specific token is expected after the path segment.
// eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
// `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
// 2. No specific token is expected after the path segment.
// eg. `x.foo` (field access)
//
// This function is called after parsing `.foo` and before parsing the token `end` (if
// present). This includes any angle bracket arguments, such as `.foo::<u32>` or
// `Foo::<Bar>`.
// We only care about trailing angle brackets if we previously parsed angle bracket
// arguments. This helps stop us incorrectly suggesting that extra angle brackets be
// removed in this case:
//
// `x.foo >> (3)` (where `x.foo` is a `u32` for example)
//
// This case is particularly tricky as we won't notice it just looking at the tokens -
// it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
// have already been parsed):
//
// `x.foo::<u32>>>(3)`
let parsed_angle_bracket_args =
segment.args.as_ref().is_some_and(|args| args.is_angle_bracketed());
debug!(
"check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
parsed_angle_bracket_args,
);
if !parsed_angle_bracket_args {
return None;
}
// Keep the span at the start so we can highlight the sequence of `>` characters to be
// removed.
let lo = self.token.span;
// We need to look-ahead to see if we have `>` characters without moving the cursor forward
// (since we might have the field access case and the characters we're eating are
// actual operators and not trailing characters - ie `x.foo >> 3`).
let mut position = 0;
// We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
// many of each (so we can correctly pluralize our error messages) and continue to
// advance.
let mut number_of_shr = 0;
let mut number_of_gt = 0;
while self.look_ahead(position, |t| {
trace!("check_trailing_angle_brackets: t={:?}", t);
if *t == token::BinOp(token::BinOpToken::Shr) {
number_of_shr += 1;
true
} else if *t == token::Gt {
number_of_gt += 1;
true
} else {
false
}
}) {
position += 1;
}
// If we didn't find any trailing `>` characters, then we have nothing to error about.
debug!(
"check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
number_of_gt, number_of_shr,
);
if number_of_gt < 1 && number_of_shr < 1 {
return None;
}
// Finally, double check that we have our end token as otherwise this is the
// second case.
if self.look_ahead(position, |t| {
trace!("check_trailing_angle_brackets: t={:?}", t);
end.contains(&&t.kind)
}) {
// Eat from where we started until the end token so that parsing can continue
// as if we didn't have those extra angle brackets.
self.eat_to_tokens(end);
let span = lo.until(self.token.span);
let num_extra_brackets = number_of_gt + number_of_shr * 2;
return Some(self.dcx().emit_err(UnmatchedAngleBrackets { span, num_extra_brackets }));
}
None
}
/// Check if a method call with an intended turbofish has been written without surrounding
/// angle brackets.
pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
if !self.may_recover() {
return;
}
if token::PathSep == self.token.kind && segment.args.is_none() {
let snapshot = self.create_snapshot_for_diagnostic();
self.bump();
let lo = self.token.span;
match self.parse_angle_args(None) {
Ok(args) => {
let span = lo.to(self.prev_token.span);
// Detect trailing `>` like in `x.collect::Vec<_>>()`.
let mut trailing_span = self.prev_token.span.shrink_to_hi();
while self.token.kind == token::BinOp(token::Shr)
|| self.token.kind == token::Gt
{
trailing_span = trailing_span.to(self.token.span);
self.bump();
}
if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
// Recover from bad turbofish: `foo.collect::Vec<_>()`.
segment.args = Some(AngleBracketedArgs { args, span }.into());
self.dcx().emit_err(GenericParamsWithoutAngleBrackets {
span,
sugg: GenericParamsWithoutAngleBracketsSugg {
left: span.shrink_to_lo(),
right: trailing_span,
},
});
} else {
// This doesn't look like an invalid turbofish, can't recover parse state.
self.restore_snapshot(snapshot);
}
}
Err(err) => {
// We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
// generic parse error instead.
err.cancel();
self.restore_snapshot(snapshot);
}
}
}
}
/// When writing a turbofish with multiple type parameters missing the leading `::`, we will
/// encounter a parse error when encountering the first `,`.
pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
&mut self,
mut e: Diag<'a>,
expr: &mut P<Expr>,
) -> PResult<'a, ErrorGuaranteed> {
if let ExprKind::Binary(binop, _, _) = &expr.kind
&& let ast::BinOpKind::Lt = binop.node
&& self.eat(&token::Comma)
{
let x = self.parse_seq_to_before_end(
&token::Gt,
SeqSep::trailing_allowed(token::Comma),
|p| p.parse_generic_arg(None),
);
match x {
Ok((_, _, Recovered::No)) => {
if self.eat(&token::Gt) {
// We made sense of it. Improve the error message.
e.span_suggestion_verbose(
binop.span.shrink_to_lo(),
fluent::parse_sugg_turbofish_syntax,
"::",
Applicability::MaybeIncorrect,
);
match self.parse_expr() {
Ok(_) => {
// The subsequent expression is valid. Mark
// `expr` as erroneous and emit `e` now, but
// return `Ok` so parsing can continue.
let guar = e.emit();
*expr = self.mk_expr_err(expr.span.to(self.prev_token.span), guar);
return Ok(guar);
}
Err(err) => {
err.cancel();
}
}
}
}
Ok((_, _, Recovered::Yes)) => {}
Err(err) => {
err.cancel();
}
}
}
Err(e)
}
/// Suggest add the missing `let` before the identifier in stmt
/// `a: Ty = 1` -> `let a: Ty = 1`
pub(super) fn suggest_add_missing_let_for_stmt(&mut self, err: &mut Diag<'a>) {
if self.token == token::Colon {
let prev_span = self.prev_token.span.shrink_to_lo();
let snapshot = self.create_snapshot_for_diagnostic();
self.bump();
match self.parse_ty() {
Ok(_) => {
if self.token == token::Eq {
let sugg = SuggAddMissingLetStmt { span: prev_span };
sugg.add_to_diag(err);
}
}
Err(e) => {
e.cancel();
}
}
self.restore_snapshot(snapshot);
}
}
/// Check to see if a pair of chained operators looks like an attempt at chained comparison,
/// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
/// parenthesising the leftmost comparison.
fn attempt_chained_comparison_suggestion(
&mut self,
err: &mut ComparisonOperatorsCannotBeChained,
inner_op: &Expr,
outer_op: &Spanned<AssocOp>,
) -> Recovered {
if let ExprKind::Binary(op, l1, r1) = &inner_op.kind {
if let ExprKind::Field(_, ident) = l1.kind
&& ident.as_str().parse::<i32>().is_err()
&& !matches!(r1.kind, ExprKind::Lit(_))
{
// The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
// suggestion being the only one to apply is high.
return Recovered::No;
}
return match (op.node, &outer_op.node) {
// `x == y == z`
(BinOpKind::Eq, AssocOp::Equal) |
// `x < y < z` and friends.
(BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
(BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
// `x > y > z` and friends.
(BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
(BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
let expr_to_str = |e: &Expr| {
self.span_to_snippet(e.span)
.unwrap_or_else(|_| pprust::expr_to_string(e))
};
err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::SplitComparison {
span: inner_op.span.shrink_to_hi(),
middle_term: expr_to_str(r1),
});
Recovered::No // Keep the current parse behavior, where the AST is `(x < y) < z`.
}
// `x == y < z`
(BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
// Consume `z`/outer-op-rhs.
let snapshot = self.create_snapshot_for_diagnostic();
match self.parse_expr() {
Ok(r2) => {
// We are sure that outer-op-rhs could be consumed, the suggestion is
// likely correct.
err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::Parenthesize {
left: r1.span.shrink_to_lo(),
right: r2.span.shrink_to_hi(),
});
Recovered::Yes
}
Err(expr_err) => {
expr_err.cancel();
self.restore_snapshot(snapshot);
Recovered::Yes
}
}
}
// `x > y == z`
(BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
let snapshot = self.create_snapshot_for_diagnostic();
// At this point it is always valid to enclose the lhs in parentheses, no
// further checks are necessary.
match self.parse_expr() {
Ok(_) => {
err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::Parenthesize {
left: l1.span.shrink_to_lo(),
right: r1.span.shrink_to_hi(),
});
Recovered::Yes
}
Err(expr_err) => {
expr_err.cancel();
self.restore_snapshot(snapshot);
Recovered::No
}
}
}
_ => Recovered::No,
};
}
Recovered::No
}
/// Produces an error if comparison operators are chained (RFC #558).
/// We only need to check the LHS, not the RHS, because all comparison ops have same
/// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
///
/// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
/// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
/// case.
///
/// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
/// associative we can infer that we have:
///
/// ```text
/// outer_op
/// / \
/// inner_op r2
/// / \
/// l1 r1
/// ```
pub(super) fn check_no_chained_comparison(
&mut self,
inner_op: &Expr,
outer_op: &Spanned<AssocOp>,
) -> PResult<'a, Option<P<Expr>>> {
debug_assert!(
outer_op.node.is_comparison(),
"check_no_chained_comparison: {:?} is not comparison",
outer_op.node,
);
let mk_err_expr =
|this: &Self, span, guar| Ok(Some(this.mk_expr(span, ExprKind::Err(guar))));
match &inner_op.kind {
ExprKind::Binary(op, l1, r1) if op.node.is_comparison() => {
let mut err = ComparisonOperatorsCannotBeChained {
span: vec![op.span, self.prev_token.span],
suggest_turbofish: None,
help_turbofish: None,
chaining_sugg: None,
};
// Include `<` to provide this recommendation even in a case like
// `Foo<Bar<Baz<Qux, ()>>>`
if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
|| outer_op.node == AssocOp::Greater
{
if outer_op.node == AssocOp::Less {
let snapshot = self.create_snapshot_for_diagnostic();
self.bump();
// So far we have parsed `foo<bar<`, consume the rest of the type args.
let modifiers =
[(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
self.consume_tts(1, &modifiers);
if !&[token::OpenDelim(Delimiter::Parenthesis), token::PathSep]
.contains(&self.token.kind)
{
// We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
// parser and bail out.
self.restore_snapshot(snapshot);
}
}
return if token::PathSep == self.token.kind {
// We have some certainty that this was a bad turbofish at this point.
// `foo< bar >::`
if let ExprKind::Binary(o, ..) = inner_op.kind
&& o.node == BinOpKind::Lt
{
err.suggest_turbofish = Some(op.span.shrink_to_lo());
} else {
err.help_turbofish = Some(());
}
let snapshot = self.create_snapshot_for_diagnostic();
self.bump(); // `::`
// Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
match self.parse_expr() {
Ok(_) => {
// 99% certain that the suggestion is correct, continue parsing.
let guar = self.dcx().emit_err(err);
// FIXME: actually check that the two expressions in the binop are
// paths and resynthesize new fn call expression instead of using
// `ExprKind::Err` placeholder.
mk_err_expr(self, inner_op.span.to(self.prev_token.span), guar)
}
Err(expr_err) => {
expr_err.cancel();
// Not entirely sure now, but we bubble the error up with the
// suggestion.
self.restore_snapshot(snapshot);
Err(self.dcx().create_err(err))
}
}
} else if token::OpenDelim(Delimiter::Parenthesis) == self.token.kind {
// We have high certainty that this was a bad turbofish at this point.
// `foo< bar >(`
if let ExprKind::Binary(o, ..) = inner_op.kind
&& o.node == BinOpKind::Lt
{
err.suggest_turbofish = Some(op.span.shrink_to_lo());
} else {
err.help_turbofish = Some(());
}
// Consume the fn call arguments.
match self.consume_fn_args() {
Err(()) => Err(self.dcx().create_err(err)),
Ok(()) => {
let guar = self.dcx().emit_err(err);
// FIXME: actually check that the two expressions in the binop are
// paths and resynthesize new fn call expression instead of using
// `ExprKind::Err` placeholder.
mk_err_expr(self, inner_op.span.to(self.prev_token.span), guar)
}
}
} else {
if !matches!(l1.kind, ExprKind::Lit(_))
&& !matches!(r1.kind, ExprKind::Lit(_))
{
// All we know is that this is `foo < bar >` and *nothing* else. Try to
// be helpful, but don't attempt to recover.
err.help_turbofish = Some(());
}
// If it looks like a genuine attempt to chain operators (as opposed to a
// misformatted turbofish, for instance), suggest a correct form.
let recovered = self
.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
if matches!(recovered, Recovered::Yes) {
let guar = self.dcx().emit_err(err);
mk_err_expr(self, inner_op.span.to(self.prev_token.span), guar)
} else {
// These cases cause too many knock-down errors, bail out (#61329).
Err(self.dcx().create_err(err))
}
};
}
let recover =
self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
let guar = self.dcx().emit_err(err);
if matches!(recover, Recovered::Yes) {
return mk_err_expr(self, inner_op.span.to(self.prev_token.span), guar);
}
}
_ => {}
}
Ok(None)
}
fn consume_fn_args(&mut self) -> Result<(), ()> {
let snapshot = self.create_snapshot_for_diagnostic();
self.bump(); // `(`
// Consume the fn call arguments.
let modifiers = [
(token::OpenDelim(Delimiter::Parenthesis), 1),
(token::CloseDelim(Delimiter::Parenthesis), -1),
];
self.consume_tts(1, &modifiers);
if self.token.kind == token::Eof {
// Not entirely sure that what we consumed were fn arguments, rollback.
self.restore_snapshot(snapshot);
Err(())
} else {
// 99% certain that the suggestion is correct, continue parsing.
Ok(())
}
}
pub(super) fn maybe_report_ambiguous_plus(&mut self, impl_dyn_multi: bool, ty: &Ty) {
if impl_dyn_multi {
self.dcx().emit_err(AmbiguousPlus { sum_ty: pprust::ty_to_string(ty), span: ty.span });
}
}
/// Swift lets users write `Ty?` to mean `Option<Ty>`. Parse the construct and recover from it.
pub(super) fn maybe_recover_from_question_mark(&mut self, ty: P<Ty>) -> P<Ty> {
if self.token == token::Question {
self.bump();
let guar = self.dcx().emit_err(QuestionMarkInType {
span: self.prev_token.span,
sugg: QuestionMarkInTypeSugg {
left: ty.span.shrink_to_lo(),
right: self.prev_token.span,
},
});
self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err(guar))
} else {
ty
}
}
/// Rust has no ternary operator (`cond ? then : else`). Parse it and try
/// to recover from it if `then` and `else` are valid expressions. Returns
/// an err if this appears to be a ternary expression.
pub(super) fn maybe_recover_from_ternary_operator(&mut self) -> PResult<'a, ()> {
if self.prev_token != token::Question {
return PResult::Ok(());
}
let lo = self.prev_token.span.lo();
let snapshot = self.create_snapshot_for_diagnostic();
if match self.parse_expr() {
Ok(_) => true,
Err(err) => {
err.cancel();
// The colon can sometimes be mistaken for type
// ascription. Catch when this happens and continue.
self.token == token::Colon
}
} {
if self.eat_noexpect(&token::Colon) {
match self.parse_expr() {
Ok(_) => {
return Err(self
.dcx()
.create_err(TernaryOperator { span: self.token.span.with_lo(lo) }));
}
Err(err) => {
err.cancel();
}
};
}
}
self.restore_snapshot(snapshot);
Ok(())
}
pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {
// Do not add `+` to expected tokens.
if !self.token.is_like_plus() {
return Ok(());
}
self.bump(); // `+`
let bounds = self.parse_generic_bounds()?;
let sum_span = ty.span.to(self.prev_token.span);
let sub = match &ty.kind {
TyKind::Ref(lifetime, mut_ty) => {
let sum_with_parens = pprust::to_string(|s| {
s.s.word("&");
s.print_opt_lifetime(lifetime);
s.print_mutability(mut_ty.mutbl, false);
s.popen();
s.print_type(&mut_ty.ty);
if !bounds.is_empty() {
s.word(" + ");
s.print_type_bounds(&bounds);
}
s.pclose()
});
BadTypePlusSub::AddParen { sum_with_parens, span: sum_span }
}
TyKind::Ptr(..) | TyKind::BareFn(..) => BadTypePlusSub::ForgotParen { span: sum_span },
_ => BadTypePlusSub::ExpectPath { span: sum_span },
};
self.dcx().emit_err(BadTypePlus { ty: pprust::ty_to_string(ty), span: sum_span, sub });
Ok(())
}
pub(super) fn recover_from_prefix_increment(
&mut self,
operand_expr: P<Expr>,
op_span: Span,
start_stmt: bool,
) -> PResult<'a, P<Expr>> {
let standalone = if start_stmt { IsStandalone::Standalone } else { IsStandalone::Subexpr };
let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
self.recover_from_inc_dec(operand_expr, kind, op_span)
}
pub(super) fn recover_from_postfix_increment(
&mut self,
operand_expr: P<Expr>,
op_span: Span,
start_stmt: bool,
) -> PResult<'a, P<Expr>> {
let kind = IncDecRecovery {
standalone: if start_stmt { IsStandalone::Standalone } else { IsStandalone::Subexpr },
op: IncOrDec::Inc,
fixity: UnaryFixity::Post,
};
self.recover_from_inc_dec(operand_expr, kind, op_span)
}
pub(super) fn recover_from_postfix_decrement(
&mut self,
operand_expr: P<Expr>,
op_span: Span,
start_stmt: bool,
) -> PResult<'a, P<Expr>> {
let kind = IncDecRecovery {
standalone: if start_stmt { IsStandalone::Standalone } else { IsStandalone::Subexpr },
op: IncOrDec::Dec,
fixity: UnaryFixity::Post,
};
self.recover_from_inc_dec(operand_expr, kind, op_span)
}
fn recover_from_inc_dec(
&mut self,
base: P<Expr>,
kind: IncDecRecovery,
op_span: Span,
) -> PResult<'a, P<Expr>> {
let mut err = self.dcx().struct_span_err(
op_span,
format!("Rust has no {} {} operator", kind.fixity, kind.op.name()),
);
err.span_label(op_span, format!("not a valid {} operator", kind.fixity));
let help_base_case = |mut err: Diag<'_, _>, base| {
err.help(format!("use `{}= 1` instead", kind.op.chr()));
err.emit();
Ok(base)
};
// (pre, post)
let spans = match kind.fixity {
UnaryFixity::Pre => (op_span, base.span.shrink_to_hi()),
UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
};
match kind.standalone {
IsStandalone::Standalone => {
self.inc_dec_standalone_suggest(kind, spans).emit_verbose(&mut err)
}
IsStandalone::Subexpr => {
let Ok(base_src) = self.span_to_snippet(base.span) else {
return help_base_case(err, base);
};
match kind.fixity {
UnaryFixity::Pre => {
self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
}
UnaryFixity::Post => {
// won't suggest since we can not handle the precedences
// for example: `a + b++` has been parsed (a + b)++ and we can not suggest here
if !matches!(base.kind, ExprKind::Binary(_, _, _)) {
self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
}
}
}
}
}
Err(err)
}
fn prefix_inc_dec_suggest(
&mut self,
base_src: String,
kind: IncDecRecovery,
(pre_span, post_span): (Span, Span),
) -> MultiSugg {
MultiSugg {
msg: format!("use `{}= 1` instead", kind.op.chr()),
patches: vec![
(pre_span, "{ ".to_string()),
(post_span, format!(" {}= 1; {} }}", kind.op.chr(), base_src)),
],
applicability: Applicability::MachineApplicable,
}
}
fn postfix_inc_dec_suggest(
&mut self,
base_src: String,
kind: IncDecRecovery,
(pre_span, post_span): (Span, Span),
) -> MultiSugg {
let tmp_var = if base_src.trim() == "tmp" { "tmp_" } else { "tmp" };
MultiSugg {
msg: format!("use `{}= 1` instead", kind.op.chr()),
patches: vec![
(pre_span, format!("{{ let {tmp_var} = ")),
(post_span, format!("; {} {}= 1; {} }}", base_src, kind.op.chr(), tmp_var)),
],
applicability: Applicability::HasPlaceholders,
}
}
fn inc_dec_standalone_suggest(
&mut self,
kind: IncDecRecovery,
(pre_span, post_span): (Span, Span),
) -> MultiSugg {
let mut patches = Vec::new();
if !pre_span.is_empty() {
patches.push((pre_span, String::new()));
}
patches.push((post_span, format!(" {}= 1", kind.op.chr())));
MultiSugg {
msg: format!("use `{}= 1` instead", kind.op.chr()),
patches,
applicability: Applicability::MachineApplicable,
}
}
/// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
/// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
/// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
&mut self,
base: P<T>,
) -> PResult<'a, P<T>> {
if !self.may_recover() {
return Ok(base);
}
// Do not add `::` to expected tokens.
if self.token == token::PathSep {
if let Some(ty) = base.to_ty() {
return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
}
}
Ok(base)
}
/// Given an already parsed `Ty`, parses the `::AssocItem` tail and
/// combines them into a `<Ty>::AssocItem` expression/pattern/type.
pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
&mut self,
ty_span: Span,
ty: P<Ty>,
) -> PResult<'a, P<T>> {
self.expect(&token::PathSep)?;
let mut path = ast::Path { segments: ThinVec::new(), span: DUMMY_SP, tokens: None };
self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
path.span = ty_span.to(self.prev_token.span);
self.dcx().emit_err(BadQPathStage2 {
span: ty_span,
wrap: WrapType { lo: ty_span.shrink_to_lo(), hi: ty_span.shrink_to_hi() },
});
let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
Ok(P(T::recovered(Some(P(QSelf { ty, path_span, position: 0 })), path)))
}
pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
if self.token.kind == TokenKind::Semi {
self.bump();
let mut err =
IncorrectSemicolon { span: self.prev_token.span, opt_help: None, name: "" };
if !items.is_empty() {
let previous_item = &items[items.len() - 1];
let previous_item_kind_name = match previous_item.kind {
// Say "braced struct" because tuple-structs and
// braceless-empty-struct declarations do take a semicolon.
ItemKind::Struct(..) => Some("braced struct"),
ItemKind::Enum(..) => Some("enum"),
ItemKind::Trait(..) => Some("trait"),
ItemKind::Union(..) => Some("union"),
_ => None,
};
if let Some(name) = previous_item_kind_name {
err.opt_help = Some(());
err.name = name;
}
}
self.dcx().emit_err(err);
true
} else {
false
}
}
/// Creates a `Diag` for an unexpected token `t` and tries to recover if it is a
/// closing delimiter.
pub(super) fn unexpected_try_recover(&mut self, t: &TokenKind) -> PResult<'a, Recovered> {
let token_str = pprust::token_kind_to_string(t);
let this_token_str = super::token_descr(&self.token);
let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
// Point at the end of the macro call when reaching end of macro arguments.
(token::Eof, Some(_)) => {
let sp = self.prev_token.span.shrink_to_hi();
(sp, sp)
}
// We don't want to point at the following span after DUMMY_SP.
// This happens when the parser finds an empty TokenStream.
_ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
// EOF, don't want to point at the following char, but rather the last token.
(token::Eof, None) => (self.prev_token.span, self.token.span),
_ => (self.prev_token.span.shrink_to_hi(), self.token.span),
};
let msg = format!(
"expected `{}`, found {}",
token_str,
match (&self.token.kind, self.subparser_name) {
(token::Eof, Some(origin)) => format!("end of {origin}"),
_ => this_token_str,
},
);
let mut err = self.dcx().struct_span_err(sp, msg);
let label_exp = format!("expected `{token_str}`");
let sm = self.psess.source_map();
if !sm.is_multiline(prev_sp.until(sp)) {
// When the spans are in the same line, it means that the only content
// between them is whitespace, point only at the found token.
err.span_label(sp, label_exp);
} else {
err.span_label(prev_sp, label_exp);
err.span_label(sp, "unexpected token");
}
Err(err)
}
pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
if self.eat(&token::Semi) || self.recover_colon_as_semi() {
return Ok(());
}
self.expect(&token::Semi).map(drop) // Error unconditionally
}
pub(super) fn recover_colon_as_semi(&mut self) -> bool {
let line_idx = |span: Span| {
self.psess
.source_map()
.span_to_lines(span)
.ok()
.and_then(|lines| Some(lines.lines.get(0)?.line_index))
};
if self.may_recover()
&& self.token == token::Colon
&& self.look_ahead(1, |next| line_idx(self.token.span) < line_idx(next.span))
{
self.dcx().emit_err(ColonAsSemi {
span: self.token.span,
type_ascription: self.psess.unstable_features.is_nightly_build().then_some(()),
});
self.bump();
return true;
}
false
}
/// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
/// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
pub(super) fn recover_incorrect_await_syntax(
&mut self,
lo: Span,
await_sp: Span,
) -> PResult<'a, P<Expr>> {
let (hi, expr, is_question) = if self.token == token::Not {
// Handle `await!(<expr>)`.
self.recover_await_macro()?
} else {
self.recover_await_prefix(await_sp)?
};
let (sp, guar) = self.error_on_incorrect_await(lo, hi, &expr, is_question);
let expr = self.mk_expr_err(lo.to(sp), guar);
self.maybe_recover_from_bad_qpath(expr)
}
fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
self.expect(&token::Not)?;
self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
let expr = self.parse_expr()?;
self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
Ok((self.prev_token.span, expr, false))
}
fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
let expr = if self.token == token::OpenDelim(Delimiter::Brace) {
// Handle `await { <expr> }`.
// This needs to be handled separately from the next arm to avoid
// interpreting `await { <expr> }?` as `<expr>?.await`.
self.parse_expr_block(None, self.token.span, BlockCheckMode::Default)
} else {
self.parse_expr()
}
.map_err(|mut err| {
err.span_label(await_sp, "while parsing this incorrect await expression");
err
})?;
Ok((expr.span, expr, is_question))
}
fn error_on_incorrect_await(
&self,
lo: Span,
hi: Span,
expr: &Expr,
is_question: bool,
) -> (Span, ErrorGuaranteed) {
let span = lo.to(hi);
let applicability = match expr.kind {
ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
_ => Applicability::MachineApplicable,
};
let guar = self.dcx().emit_err(IncorrectAwait {
span,
sugg_span: (span, applicability),
expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(expr)),
question_mark: if is_question { "?" } else { "" },
});
(span, guar)
}
/// If encountering `future.await()`, consumes and emits an error.
pub(super) fn recover_from_await_method_call(&mut self) {
if self.token == token::OpenDelim(Delimiter::Parenthesis)
&& self.look_ahead(1, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
{
// future.await()
let lo = self.token.span;
self.bump(); // (
let span = lo.to(self.token.span);
self.bump(); // )
self.dcx().emit_err(IncorrectUseOfAwait { span });
}
}
pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
let is_try = self.token.is_keyword(kw::Try);
let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(Delimiter::Parenthesis)); //check for (
if is_try && is_questionmark && is_open {
let lo = self.token.span;
self.bump(); //remove try
self.bump(); //remove !
let try_span = lo.to(self.token.span); //we take the try!( span
self.bump(); //remove (
let is_empty = self.token == token::CloseDelim(Delimiter::Parenthesis); //check if the block is empty
self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::No); //eat the block
let hi = self.token.span;
self.bump(); //remove )
let mut err = self.dcx().struct_span_err(lo.to(hi), "use of deprecated `try` macro");
err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
let prefix = if is_empty { "" } else { "alternatively, " };
if !is_empty {
err.multipart_suggestion(
"you can use the `?` operator instead",
vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
Applicability::MachineApplicable,
);
}
err.span_suggestion(lo.shrink_to_lo(), format!("{prefix}you can still access the deprecated `try!()` macro using the \"raw identifier\" syntax"), "r#", Applicability::MachineApplicable);
let guar = err.emit();
Ok(self.mk_expr_err(lo.to(hi), guar))
} else {
Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
}
}
/// When trying to close a generics list and encountering code like
/// ```text
/// impl<S: Into<std::borrow::Cow<'static, str>> From<S> for Canonical {}
/// // ^ missing > here
/// ```
/// we provide a structured suggestion on the error from `expect_gt`.
pub(super) fn expect_gt_or_maybe_suggest_closing_generics(
&mut self,
params: &[ast::GenericParam],
) -> PResult<'a, ()> {
let Err(mut err) = self.expect_gt() else {
return Ok(());
};
// Attempt to find places where a missing `>` might belong.
if let [.., ast::GenericParam { bounds, .. }] = params
&& let Some(poly) = bounds
.iter()
.filter_map(|bound| match bound {
ast::GenericBound::Trait(poly, _) => Some(poly),
_ => None,
})
.last()
{
err.span_suggestion_verbose(
poly.span.shrink_to_hi(),
"you might have meant to end the type parameters here",
">",
Applicability::MaybeIncorrect,
);
}
Err(err)
}
pub(super) fn recover_seq_parse_error(
&mut self,
delim: Delimiter,
lo: Span,
err: PErr<'a>,
) -> P<Expr> {
let guar = err.emit();
// Recover from parse error, callers expect the closing delim to be consumed.
self.consume_block(delim, ConsumeClosingDelim::Yes);
self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err(guar))
}
/// Eats tokens until we can be relatively sure we reached the end of the
/// statement. This is something of a best-effort heuristic.
///
/// We terminate when we find an unmatched `}` (without consuming it).
pub(super) fn recover_stmt(&mut self) {
self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
}
/// If `break_on_semi` is `Break`, then we will stop consuming tokens after
/// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
/// approximate -- it can mean we break too early due to macros, but that
/// should only lead to sub-optimal recovery, not inaccurate parsing).
///
/// If `break_on_block` is `Break`, then we will stop consuming tokens
/// after finding (and consuming) a brace-delimited block.
pub(super) fn recover_stmt_(
&mut self,
break_on_semi: SemiColonMode,
break_on_block: BlockMode,
) {
let mut brace_depth = 0;
let mut bracket_depth = 0;
let mut in_block = false;
debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
loop {
debug!("recover_stmt_ loop {:?}", self.token);
match self.token.kind {
token::OpenDelim(Delimiter::Brace) => {
brace_depth += 1;
self.bump();
if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
{
in_block = true;
}
}
token::OpenDelim(Delimiter::Bracket) => {
bracket_depth += 1;
self.bump();
}
token::CloseDelim(Delimiter::Brace) => {
if brace_depth == 0 {
debug!("recover_stmt_ return - close delim {:?}", self.token);
break;
}
brace_depth -= 1;
self.bump();
if in_block && bracket_depth == 0 && brace_depth == 0 {
debug!("recover_stmt_ return - block end {:?}", self.token);
break;
}
}
token::CloseDelim(Delimiter::Bracket) => {
bracket_depth -= 1;
if bracket_depth < 0 {
bracket_depth = 0;
}
self.bump();
}
token::Eof => {
debug!("recover_stmt_ return - Eof");
break;
}
token::Semi => {
self.bump();
if break_on_semi == SemiColonMode::Break
&& brace_depth == 0
&& bracket_depth == 0
{
debug!("recover_stmt_ return - Semi");
break;
}
}
token::Comma
if break_on_semi == SemiColonMode::Comma
&& brace_depth == 0
&& bracket_depth == 0 =>
{
break;
}
_ => self.bump(),
}
}
}
pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
if self.eat_keyword(kw::In) {
// a common typo: `for _ in in bar {}`
self.dcx().emit_err(InInTypo {
span: self.prev_token.span,
sugg_span: in_span.until(self.prev_token.span),
});
}
}
pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
if let token::DocComment(..) = self.token.kind {
self.dcx().emit_err(DocCommentOnParamType { span: self.token.span });
self.bump();
} else if self.token == token::Pound
&& self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Bracket))
{
let lo = self.token.span;
// Skip every token until next possible arg.
while self.token != token::CloseDelim(Delimiter::Bracket) {
self.bump();
}
let sp = lo.to(self.token.span);
self.bump();
self.dcx().emit_err(AttributeOnParamType { span: sp });
}
}
pub(super) fn parameter_without_type(
&mut self,
err: &mut Diag<'_>,
pat: P<ast::Pat>,
require_name: bool,
first_param: bool,
) -> Option<Ident> {
// If we find a pattern followed by an identifier, it could be an (incorrect)
// C-style parameter declaration.
if self.check_ident()
&& self.look_ahead(1, |t| {
*t == token::Comma || *t == token::CloseDelim(Delimiter::Parenthesis)
})
{
// `fn foo(String s) {}`
let ident = self.parse_ident().unwrap();
let span = pat.span.with_hi(ident.span.hi());
err.span_suggestion(
span,
"declare the type after the parameter binding",
"<identifier>: <type>",
Applicability::HasPlaceholders,
);
return Some(ident);
} else if require_name
&& (self.token == token::Comma
|| self.token == token::Lt
|| self.token == token::CloseDelim(Delimiter::Parenthesis))
{
let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
match pat.kind {
PatKind::Ident(_, ident, _) => (
ident,
"self: ",
": TypeName".to_string(),
"_: ",
pat.span.shrink_to_lo(),
pat.span.shrink_to_hi(),
pat.span.shrink_to_lo(),
),
// Also catches `fn foo(&a)`.
PatKind::Ref(ref inner_pat, mutab)
if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
{
match inner_pat.clone().into_inner().kind {
PatKind::Ident(_, ident, _) => {
let mutab = mutab.prefix_str();
(
ident,
"self: ",
format!("{ident}: &{mutab}TypeName"),
"_: ",
pat.span.shrink_to_lo(),
pat.span,
pat.span.shrink_to_lo(),
)
}
_ => unreachable!(),
}
}
_ => {
// Otherwise, try to get a type and emit a suggestion.
if let Some(ty) = pat.to_ty() {
err.span_suggestion_verbose(
pat.span,
"explicitly ignore the parameter name",
format!("_: {}", pprust::ty_to_string(&ty)),
Applicability::MachineApplicable,
);
err.note(rfc_note);
}
return None;
}
};
// `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
if first_param {
err.span_suggestion(
self_span,
"if this is a `self` type, give it a parameter name",
self_sugg,
Applicability::MaybeIncorrect,
);
}
// Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
// `fn foo(HashMap: TypeName<u32>)`.
if self.token != token::Lt {
err.span_suggestion(
param_span,
"if this is a parameter name, give it a type",
param_sugg,
Applicability::HasPlaceholders,
);
}
err.span_suggestion(
type_span,
"if this is a type, explicitly ignore the parameter name",
type_sugg,
Applicability::MachineApplicable,
);
err.note(rfc_note);
// Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
return if self.token == token::Lt { None } else { Some(ident) };
}
None
}
pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
let pat = self.parse_pat_no_top_alt(Some(Expected::ArgumentName), None)?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
self.dcx().emit_err(PatternMethodParamWithoutBody { span: pat.span });
// Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
let pat =
P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
Ok((pat, ty))
}
pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
let span = param.pat.span;
let guar = self.dcx().emit_err(SelfParamNotFirst { span });
param.ty.kind = TyKind::Err(guar);
Ok(param)
}
pub(super) fn consume_block(&mut self, delim: Delimiter, consume_close: ConsumeClosingDelim) {
let mut brace_depth = 0;
loop {
if self.eat(&token::OpenDelim(delim)) {
brace_depth += 1;
} else if self.check(&token::CloseDelim(delim)) {
if brace_depth == 0 {
if let ConsumeClosingDelim::Yes = consume_close {
// Some of the callers of this method expect to be able to parse the
// closing delimiter themselves, so we leave it alone. Otherwise we advance
// the parser.
self.bump();
}
return;
} else {
self.bump();
brace_depth -= 1;
continue;
}
} else if self.token == token::Eof {
return;
} else {
self.bump();
}
}
}
pub(super) fn expected_expression_found(&self) -> Diag<'a> {
let (span, msg) = match (&self.token.kind, self.subparser_name) {
(&token::Eof, Some(origin)) => {
let sp = self.prev_token.span.shrink_to_hi();
(sp, format!("expected expression, found end of {origin}"))
}
_ => (
self.token.span,
format!("expected expression, found {}", super::token_descr(&self.token)),
),
};
let mut err = self.dcx().struct_span_err(span, msg);
let sp = self.psess.source_map().start_point(self.token.span);
if let Some(sp) = self.psess.ambiguous_block_expr_parse.borrow().get(&sp) {
err.subdiagnostic(self.dcx(), ExprParenthesesNeeded::surrounding(*sp));
}
err.span_label(span, "expected expression");
// Walk the chain of macro expansions for the current token to point at how the original
// code was interpreted. This helps the user realize when a macro argument of one type is
// later reinterpreted as a different type, like `$x:expr` being reinterpreted as `$x:pat`
// in a subsequent macro invocation (#71039).
let mut tok = self.token.clone();
let mut labels = vec![];
while let TokenKind::Interpolated(node) = &tok.kind {
let tokens = node.0.tokens();
labels.push(node.clone());
if let Some(tokens) = tokens
&& let tokens = tokens.to_attr_token_stream()
&& let tokens = tokens.0.deref()
&& let [AttrTokenTree::Token(token, _)] = &tokens[..]
{
tok = token.clone();
} else {
break;
}
}
let mut iter = labels.into_iter().peekable();
let mut show_link = false;
while let Some(node) = iter.next() {
let descr = node.0.descr();
if let Some(next) = iter.peek() {
let next_descr = next.0.descr();
if next_descr != descr {
err.span_label(next.1, format!("this macro fragment matcher is {next_descr}"));
err.span_label(node.1, format!("this macro fragment matcher is {descr}"));
err.span_label(
next.0.use_span(),
format!("this is expected to be {next_descr}"),
);
err.span_label(
node.0.use_span(),
format!(
"this is interpreted as {}, but it is expected to be {}",
next_descr, descr,
),
);
show_link = true;
} else {
err.span_label(node.1, "");
}
}
}
if show_link {
err.note(
"when forwarding a matched fragment to another macro-by-example, matchers in the \
second macro will see an opaque AST of the fragment type, not the underlying \
tokens",
);
}
err
}
fn consume_tts(
&mut self,
mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
// Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
modifier: &[(token::TokenKind, i64)],
) {
while acc > 0 {
if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
acc += *val;
}
if self.token.kind == token::Eof {
break;
}
self.bump();
}
}
/// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
///
/// This is necessary because at this point we don't know whether we parsed a function with
/// anonymous parameters or a function with names but no types. In order to minimize
/// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
/// the parameters are *names* (so we don't emit errors about not being able to find `b` in
/// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
/// we deduplicate them to not complain about duplicated parameter names.
pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut ThinVec<Param>) {
let mut seen_inputs = FxHashSet::default();
for input in fn_inputs.iter_mut() {
let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err(_)) =
(&input.pat.kind, &input.ty.kind)
{
Some(*ident)
} else {
None
};
if let Some(ident) = opt_ident {
if seen_inputs.contains(&ident) {
input.pat.kind = PatKind::Wild;
}
seen_inputs.insert(ident);
}
}
}
/// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
/// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
/// like the user has forgotten them.
pub fn handle_ambiguous_unbraced_const_arg(
&mut self,
args: &mut ThinVec<AngleBracketedArg>,
) -> PResult<'a, bool> {
// If we haven't encountered a closing `>`, then the argument is malformed.
// It's likely that the user has written a const expression without enclosing it
// in braces, so we try to recover here.
let arg = args.pop().unwrap();
// FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
// adverse side-effects to subsequent errors and seems to advance the parser.
// We are causing this error here exclusively in case that a `const` expression
// could be recovered from the current parser state, even if followed by more
// arguments after a comma.
let mut err = self.dcx().struct_span_err(
self.token.span,
format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
);
err.span_label(self.token.span, "expected one of `,` or `>`");
match self.recover_const_arg(arg.span(), err) {
Ok(arg) => {
args.push(AngleBracketedArg::Arg(arg));
if self.eat(&token::Comma) {
return Ok(true); // Continue
}
}
Err(err) => {
args.push(arg);
// We will emit a more generic error later.
err.delay_as_bug();
}
}
return Ok(false); // Don't continue.
}
/// Attempt to parse a generic const argument that has not been enclosed in braces.
/// There are a limited number of expressions that are permitted without being encoded
/// in braces:
/// - Literals.
/// - Single-segment paths (i.e. standalone generic const parameters).
/// All other expressions that can be parsed will emit an error suggesting the expression be
/// wrapped in braces.
pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
let start = self.token.span;
let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
err.span_label(
start.shrink_to_lo(),
"while parsing a const generic argument starting here",
);
err
})?;
if !self.expr_is_valid_const_arg(&expr) {
self.dcx().emit_err(ConstGenericWithoutBraces {
span: expr.span,
sugg: ConstGenericWithoutBracesSugg {
left: expr.span.shrink_to_lo(),
right: expr.span.shrink_to_hi(),
},
});
}
Ok(expr)
}
fn recover_const_param_decl(&mut self, ty_generics: Option<&Generics>) -> Option<GenericArg> {
let snapshot = self.create_snapshot_for_diagnostic();
let param = match self.parse_const_param(AttrVec::new()) {
Ok(param) => param,
Err(err) => {
err.cancel();
self.restore_snapshot(snapshot);
return None;
}
};
let ident = param.ident.to_string();
let sugg = match (ty_generics, self.psess.source_map().span_to_snippet(param.span())) {
(Some(Generics { params, span: impl_generics, .. }), Ok(snippet)) => {
Some(match &params[..] {
[] => UnexpectedConstParamDeclarationSugg::AddParam {
impl_generics: *impl_generics,
incorrect_decl: param.span(),
snippet,
ident,
},
[.., generic] => UnexpectedConstParamDeclarationSugg::AppendParam {
impl_generics_end: generic.span().shrink_to_hi(),
incorrect_decl: param.span(),
snippet,
ident,
},
})
}
_ => None,
};
let guar =
self.dcx().emit_err(UnexpectedConstParamDeclaration { span: param.span(), sugg });
let value = self.mk_expr_err(param.span(), guar);
Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }))
}
pub fn recover_const_param_declaration(
&mut self,
ty_generics: Option<&Generics>,
) -> PResult<'a, Option<GenericArg>> {
// We have to check for a few different cases.
if let Some(arg) = self.recover_const_param_decl(ty_generics) {
return Ok(Some(arg));
}
// We haven't consumed `const` yet.
let start = self.token.span;
self.bump(); // `const`
// Detect and recover from the old, pre-RFC2000 syntax for const generics.
let mut err = UnexpectedConstInGenericParam { span: start, to_remove: None };
if self.check_const_arg() {
err.to_remove = Some(start.until(self.token.span));
self.dcx().emit_err(err);
Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
} else {
let after_kw_const = self.token.span;
self.recover_const_arg(after_kw_const, self.dcx().create_err(err)).map(Some)
}
}
/// Try to recover from possible generic const argument without `{` and `}`.
///
/// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
/// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
/// if we think that the resulting expression would be well formed.
pub fn recover_const_arg(&mut self, start: Span, mut err: Diag<'a>) -> PResult<'a, GenericArg> {
let is_op_or_dot = AssocOp::from_token(&self.token)
.and_then(|op| {
if let AssocOp::Greater
| AssocOp::Less
| AssocOp::ShiftRight
| AssocOp::GreaterEqual
// Don't recover from `foo::<bar = baz>`, because this could be an attempt to
// assign a value to a defaulted generic parameter.
| AssocOp::Assign
| AssocOp::AssignOp(_) = op
{
None
} else {
Some(op)
}
})
.is_some()
|| self.token.kind == TokenKind::Dot;
// This will be true when a trait object type `Foo +` or a path which was a `const fn` with
// type params has been parsed.
let was_op =
matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
if !is_op_or_dot && !was_op {
// We perform these checks and early return to avoid taking a snapshot unnecessarily.
return Err(err);
}
let snapshot = self.create_snapshot_for_diagnostic();
if is_op_or_dot {
self.bump();
}
match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
Ok(expr) => {
// Find a mistake like `MyTrait<Assoc == S::Assoc>`.
if token::EqEq == snapshot.token.kind {
err.span_suggestion(
snapshot.token.span,
"if you meant to use an associated type binding, replace `==` with `=`",
"=",
Applicability::MaybeIncorrect,
);
let guar = err.emit();
let value = self.mk_expr_err(start.to(expr.span), guar);
return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
} else if token::Colon == snapshot.token.kind
&& expr.span.lo() == snapshot.token.span.hi()
&& matches!(expr.kind, ExprKind::Path(..))
{
// Find a mistake like "foo::var:A".
err.span_suggestion(
snapshot.token.span,
"write a path separator here",
"::",
Applicability::MaybeIncorrect,
);
let guar = err.emit();
return Ok(GenericArg::Type(
self.mk_ty(start.to(expr.span), TyKind::Err(guar)),
));
} else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
{
// Avoid the following output by checking that we consumed a full const arg:
// help: expressions must be enclosed in braces to be used as const generic
// arguments
// |
// LL | let sr: Vec<{ (u32, _, _) = vec![] };
// | ^ ^
return Ok(self.dummy_const_arg_needs_braces(err, start.to(expr.span)));
}
}
Err(err) => {
err.cancel();
}
}
self.restore_snapshot(snapshot);
Err(err)
}
/// Try to recover from an unbraced const argument whose first token [could begin a type][ty].
///
/// [ty]: token::Token::can_begin_type
pub(crate) fn recover_unbraced_const_arg_that_can_begin_ty(
&mut self,
mut snapshot: SnapshotParser<'a>,
) -> Option<P<ast::Expr>> {
match snapshot.parse_expr_res(Restrictions::CONST_EXPR, None) {
// Since we don't know the exact reason why we failed to parse the type or the
// expression, employ a simple heuristic to weed out some pathological cases.
Ok(expr) if let token::Comma | token::Gt = snapshot.token.kind => {
self.restore_snapshot(snapshot);
Some(expr)
}
Ok(_) => None,
Err(err) => {
err.cancel();
None
}
}
}
/// Creates a dummy const argument, and reports that the expression must be enclosed in braces
pub fn dummy_const_arg_needs_braces(&self, mut err: Diag<'a>, span: Span) -> GenericArg {
err.multipart_suggestion(
"expressions must be enclosed in braces to be used as const generic \
arguments",
vec![(span.shrink_to_lo(), "{ ".to_string()), (span.shrink_to_hi(), " }".to_string())],
Applicability::MaybeIncorrect,
);
let guar = err.emit();
let value = self.mk_expr_err(span, guar);
GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })
}
/// Some special error handling for the "top-level" patterns in a match arm,
/// `for` loop, `let`, &c. (in contrast to subpatterns within such).
pub(crate) fn maybe_recover_colon_colon_in_pat_typo(
&mut self,
mut first_pat: P<Pat>,
expected: Option<Expected>,
) -> P<Pat> {
if token::Colon != self.token.kind {
return first_pat;
}
if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
|| !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
{
let mut snapshot_type = self.create_snapshot_for_diagnostic();
snapshot_type.bump(); // `:`
match snapshot_type.parse_ty() {
Err(inner_err) => {
inner_err.cancel();
}
Ok(ty) => {
let Err(mut err) = self.expected_one_of_not_found(&[], &[]) else {
return first_pat;
};
err.span_label(ty.span, "specifying the type of a pattern isn't supported");
self.restore_snapshot(snapshot_type);
let span = first_pat.span.to(ty.span);
first_pat = self.mk_pat(span, PatKind::Wild);
err.emit();
}
}
return first_pat;
}
// The pattern looks like it might be a path with a `::` -> `:` typo:
// `match foo { bar:baz => {} }`
let colon_span = self.token.span;
// We only emit "unexpected `:`" error here if we can successfully parse the
// whole pattern correctly in that case.
let mut snapshot_pat = self.create_snapshot_for_diagnostic();
let mut snapshot_type = self.create_snapshot_for_diagnostic();
// Create error for "unexpected `:`".
match self.expected_one_of_not_found(&[], &[]) {
Err(mut err) => {
// Skip the `:`.
snapshot_pat.bump();
snapshot_type.bump();
match snapshot_pat.parse_pat_no_top_alt(expected, None) {
Err(inner_err) => {
inner_err.cancel();
}
Ok(mut pat) => {
// We've parsed the rest of the pattern.
let new_span = first_pat.span.to(pat.span);
let mut show_sugg = false;
// Try to construct a recovered pattern.
match &mut pat.kind {
PatKind::Struct(qself @ None, path, ..)
| PatKind::TupleStruct(qself @ None, path, _)
| PatKind::Path(qself @ None, path) => match &first_pat.kind {
PatKind::Ident(_, ident, _) => {
path.segments.insert(0, PathSegment::from_ident(*ident));
path.span = new_span;
show_sugg = true;
first_pat = pat;
}
PatKind::Path(old_qself, old_path) => {
path.segments = old_path
.segments
.iter()
.cloned()
.chain(take(&mut path.segments))
.collect();
path.span = new_span;
*qself = old_qself.clone();
first_pat = pat;
show_sugg = true;
}
_ => {}
},
PatKind::Ident(BindingMode::NONE, ident, None) => {
match &first_pat.kind {
PatKind::Ident(_, old_ident, _) => {
let path = PatKind::Path(
None,
Path {
span: new_span,
segments: thin_vec![
PathSegment::from_ident(*old_ident),
PathSegment::from_ident(*ident),
],
tokens: None,
},
);
first_pat = self.mk_pat(new_span, path);
show_sugg = true;
}
PatKind::Path(old_qself, old_path) => {
let mut segments = old_path.segments.clone();
segments.push(PathSegment::from_ident(*ident));
let path = PatKind::Path(
old_qself.clone(),
Path { span: new_span, segments, tokens: None },
);
first_pat = self.mk_pat(new_span, path);
show_sugg = true;
}
_ => {}
}
}
_ => {}
}
if show_sugg {
err.span_suggestion_verbose(
colon_span.until(self.look_ahead(1, |t| t.span)),
"maybe write a path separator here",
"::",
Applicability::MaybeIncorrect,
);
} else {
first_pat = self.mk_pat(new_span, PatKind::Wild);
}
self.restore_snapshot(snapshot_pat);
}
}
match snapshot_type.parse_ty() {
Err(inner_err) => {
inner_err.cancel();
}
Ok(ty) => {
err.span_label(ty.span, "specifying the type of a pattern isn't supported");
self.restore_snapshot(snapshot_type);
let new_span = first_pat.span.to(ty.span);
first_pat = self.mk_pat(new_span, PatKind::Wild);
}
}
err.emit();
}
_ => {
// Carry on as if we had not done anything. This should be unreachable.
}
};
first_pat
}
pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
// Check for `'a : {`
if !(self.check_lifetime()
&& self.look_ahead(1, |tok| tok.kind == token::Colon)
&& self.look_ahead(2, |tok| tok.kind == token::OpenDelim(Delimiter::Brace)))
{
return false;
}
let label = self.eat_label().expect("just checked if a label exists");
self.bump(); // eat `:`
let span = label.ident.span.to(self.prev_token.span);
self.dcx()
.struct_span_err(span, "block label not supported here")
.with_span_label(span, "not supported here")
.with_tool_only_span_suggestion(
label.ident.span.until(self.token.span),
"remove this block label",
"",
Applicability::MachineApplicable,
)
.emit();
true
}
/// Some special error handling for the "top-level" patterns in a match arm,
/// `for` loop, `let`, &c. (in contrast to subpatterns within such).
pub(crate) fn maybe_recover_unexpected_comma(
&mut self,
lo: Span,
rt: CommaRecoveryMode,
) -> PResult<'a, ()> {
if self.token != token::Comma {
return Ok(());
}
// An unexpected comma after a top-level pattern is a clue that the
// user (perhaps more accustomed to some other language) forgot the
// parentheses in what should have been a tuple pattern; return a
// suggestion-enhanced error here rather than choking on the comma later.
let comma_span = self.token.span;
self.bump();
if let Err(err) = self.skip_pat_list() {
// We didn't expect this to work anyway; we just wanted to advance to the
// end of the comma-sequence so we know the span to suggest parenthesizing.
err.cancel();
}
let seq_span = lo.to(self.prev_token.span);
let mut err = self.dcx().struct_span_err(comma_span, "unexpected `,` in pattern");
if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
err.multipart_suggestion(
format!(
"try adding parentheses to match on a tuple{}",
if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
),
vec![
(seq_span.shrink_to_lo(), "(".to_string()),
(seq_span.shrink_to_hi(), ")".to_string()),
],
Applicability::MachineApplicable,
);
if let CommaRecoveryMode::EitherTupleOrPipe = rt {
err.span_suggestion(
seq_span,
"...or a vertical bar to match on multiple alternatives",
seq_snippet.replace(',', " |"),
Applicability::MachineApplicable,
);
}
}
Err(err)
}
pub(crate) fn maybe_recover_bounds_doubled_colon(&mut self, ty: &Ty) -> PResult<'a, ()> {
let TyKind::Path(qself, path) = &ty.kind else { return Ok(()) };
let qself_position = qself.as_ref().map(|qself| qself.position);
for (i, segments) in path.segments.windows(2).enumerate() {
if qself_position.is_some_and(|pos| i < pos) {
continue;
}
if let [a, b] = segments {
let (a_span, b_span) = (a.span(), b.span());
let between_span = a_span.shrink_to_hi().to(b_span.shrink_to_lo());
if self.span_to_snippet(between_span).as_deref() == Ok(":: ") {
return Err(self.dcx().create_err(DoubleColonInBound {
span: path.span.shrink_to_hi(),
between: between_span,
}));
}
}
}
Ok(())
}
/// Check for exclusive ranges written as `..<`
pub(crate) fn maybe_err_dotdotlt_syntax(&self, maybe_lt: Token, mut err: PErr<'a>) -> PErr<'a> {
if maybe_lt == token::Lt
&& (self.expected_tokens.contains(&TokenType::Token(token::Gt))
|| matches!(self.token.kind, token::Literal(..)))
{
err.span_suggestion(
maybe_lt.span,
"remove the `<` to write an exclusive range",
"",
Applicability::MachineApplicable,
);
}
err
}
pub fn is_diff_marker(&mut self, long_kind: &TokenKind, short_kind: &TokenKind) -> bool {
(0..3).all(|i| self.look_ahead(i, |tok| tok == long_kind))
&& self.look_ahead(3, |tok| tok == short_kind)
}
fn diff_marker(&mut self, long_kind: &TokenKind, short_kind: &TokenKind) -> Option<Span> {
if self.is_diff_marker(long_kind, short_kind) {
let lo = self.token.span;
for _ in 0..4 {
self.bump();
}
return Some(lo.to(self.prev_token.span));
}
None
}
pub fn recover_diff_marker(&mut self) {
if let Err(err) = self.err_diff_marker() {
err.emit();
FatalError.raise();
}
}
pub fn err_diff_marker(&mut self) -> PResult<'a, ()> {
let Some(start) = self.diff_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt) else {
return Ok(());
};
let mut spans = Vec::with_capacity(3);
spans.push(start);
let mut middlediff3 = None;
let mut middle = None;
let mut end = None;
loop {
if self.token.kind == TokenKind::Eof {
break;
}
if let Some(span) = self.diff_marker(&TokenKind::OrOr, &TokenKind::BinOp(token::Or)) {
middlediff3 = Some(span);
}
if let Some(span) = self.diff_marker(&TokenKind::EqEq, &TokenKind::Eq) {
middle = Some(span);
}
if let Some(span) = self.diff_marker(&TokenKind::BinOp(token::Shr), &TokenKind::Gt) {
spans.push(span);
end = Some(span);
break;
}
self.bump();
}
let mut err = self.dcx().struct_span_err(spans, "encountered diff marker");
err.span_label(start, "after this is the code before the merge");
if let Some(middle) = middlediff3 {
err.span_label(middle, "");
}
if let Some(middle) = middle {
err.span_label(middle, "");
}
if let Some(end) = end {
err.span_label(end, "above this are the incoming code changes");
}
err.help(
"if you're having merge conflicts after pulling new code, the top section is the code \
you already had and the bottom section is the remote code",
);
err.help(
"if you're in the middle of a rebase, the top section is the code being rebased onto \
and the bottom section is the code coming from the current commit being rebased",
);
err.note(
"for an explanation on these markers from the `git` documentation, visit \
<https://git-scm.com/book/en/v2/Git-Tools-Advanced-Merging#_checking_out_conflicts>",
);
Err(err)
}
/// Parse and throw away a parenthesized comma separated
/// sequence of patterns until `)` is reached.
fn skip_pat_list(&mut self) -> PResult<'a, ()> {
while !self.check(&token::CloseDelim(Delimiter::Parenthesis)) {
self.parse_pat_no_top_alt(None, None)?;
if !self.eat(&token::Comma) {
return Ok(());
}
}
Ok(())
}
}