move diagnostics.rs into parser/

1 files changed, 0 insertions, 1483 deletions

diff --git a/src/libsyntax/parse/diagnostics.rs b/src/libsyntax/parse/diagnostics.rs
deleted file mode 100644
index 943838d9dda..00000000000
--- a/src/libsyntax/parse/diagnostics.rs
+++ /dev/null
@@ -1,1483 +0,0 @@
-use crate::ast::{
-    self, Param, BinOpKind, BindingMode, BlockCheckMode, Expr, ExprKind, Ident, Item, ItemKind,
-    Mutability, Pat, PatKind, PathSegment, QSelf, Ty, TyKind,
-};
-use crate::parse::{SeqSep, PResult, Parser};
-use crate::parse::parser::{BlockMode, PathStyle, SemiColonMode, TokenType, TokenExpectType};
-use crate::parse::token::{self, TokenKind};
-use crate::print::pprust;
-use crate::ptr::P;
-use crate::symbol::{kw, sym};
-use crate::ThinVec;
-use crate::util::parser::AssocOp;
-use errors::{Applicability, DiagnosticBuilder, DiagnosticId, pluralise};
-use rustc_data_structures::fx::FxHashSet;
-use syntax_pos::{Span, DUMMY_SP, MultiSpan, SpanSnippetError};
-use log::{debug, trace};
-use std::mem;
-
-const TURBOFISH: &'static str = "use `::<...>` instead of `<...>` to specify type arguments";
-/// Creates a placeholder argument.
-crate fn dummy_arg(ident: Ident) -> Param {
-    let pat = P(Pat {
-        id: ast::DUMMY_NODE_ID,
-        kind: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
-        span: ident.span,
-    });
-    let ty = Ty {
-        kind: TyKind::Err,
-        span: ident.span,
-        id: ast::DUMMY_NODE_ID
-    };
-    Param {
-        attrs: ThinVec::default(),
-        id: ast::DUMMY_NODE_ID,
-        pat,
-        span: ident.span,
-        ty: P(ty),
-        is_placeholder: false,
-    }
-}
-
-pub enum Error {
-    FileNotFoundForModule {
-        mod_name: String,
-        default_path: String,
-        secondary_path: String,
-        dir_path: String,
-    },
-    DuplicatePaths {
-        mod_name: String,
-        default_path: String,
-        secondary_path: String,
-    },
-    UselessDocComment,
-    InclusiveRangeWithNoEnd,
-}
-
-impl Error {
-    fn span_err<S: Into<MultiSpan>>(
-        self,
-        sp: S,
-        handler: &errors::Handler,
-    ) -> DiagnosticBuilder<'_> {
-        match self {
-            Error::FileNotFoundForModule {
-                ref mod_name,
-                ref default_path,
-                ref secondary_path,
-                ref dir_path,
-            } => {
-                let mut err = struct_span_err!(
-                    handler,
-                    sp,
-                    E0583,
-                    "file not found for module `{}`",
-                    mod_name,
-                );
-                err.help(&format!(
-                    "name the file either {} or {} inside the directory \"{}\"",
-                    default_path,
-                    secondary_path,
-                    dir_path,
-                ));
-                err
-            }
-            Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
-                let mut err = struct_span_err!(
-                    handler,
-                    sp,
-                    E0584,
-                    "file for module `{}` found at both {} and {}",
-                    mod_name,
-                    default_path,
-                    secondary_path,
-                );
-                err.help("delete or rename one of them to remove the ambiguity");
-                err
-            }
-            Error::UselessDocComment => {
-                let mut err = struct_span_err!(
-                    handler,
-                    sp,
-                    E0585,
-                    "found a documentation comment that doesn't document anything",
-                );
-                err.help("doc comments must come before what they document, maybe a comment was \
-                          intended with `//`?");
-                err
-            }
-            Error::InclusiveRangeWithNoEnd => {
-                let mut err = struct_span_err!(
-                    handler,
-                    sp,
-                    E0586,
-                    "inclusive range with no end",
-                );
-                err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
-                err
-            }
-        }
-    }
-}
-
-pub trait RecoverQPath: Sized + 'static {
-    const PATH_STYLE: PathStyle = PathStyle::Expr;
-    fn to_ty(&self) -> Option<P<Ty>>;
-    fn recovered(qself: Option<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<QSelf>, path: ast::Path) -> Self {
-        Self {
-            span: path.span,
-            kind: TyKind::Path(qself, path),
-            id: ast::DUMMY_NODE_ID,
-        }
-    }
-}
-
-impl RecoverQPath for Pat {
-    fn to_ty(&self) -> Option<P<Ty>> {
-        self.to_ty()
-    }
-    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
-        Self {
-            span: path.span,
-            kind: PatKind::Path(qself, path),
-            id: ast::DUMMY_NODE_ID,
-        }
-    }
-}
-
-impl RecoverQPath for Expr {
-    fn to_ty(&self) -> Option<P<Ty>> {
-        self.to_ty()
-    }
-    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
-        Self {
-            span: path.span,
-            kind: ExprKind::Path(qself, path),
-            attrs: ThinVec::new(),
-            id: ast::DUMMY_NODE_ID,
-        }
-    }
-}
-
-impl<'a> Parser<'a> {
-    pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
-        self.span_fatal(self.token.span, m)
-    }
-
-    pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_fatal(sp, m)
-    }
-
-    pub fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
-        err.span_err(sp, self.diagnostic())
-    }
-
-    pub fn bug(&self, m: &str) -> ! {
-        self.sess.span_diagnostic.span_bug(self.token.span, m)
-    }
-
-    pub fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
-        self.sess.span_diagnostic.span_err(sp, m)
-    }
-
-    crate fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_err(sp, m)
-    }
-
-    crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
-        self.sess.span_diagnostic.span_bug(sp, m)
-    }
-
-    crate fn diagnostic(&self) -> &'a errors::Handler {
-        &self.sess.span_diagnostic
-    }
-
-    crate fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
-        self.sess.source_map().span_to_snippet(span)
-    }
-
-    crate fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
-        let mut err = self.struct_span_err(
-            self.token.span,
-            &format!("expected identifier, found {}", self.this_token_descr()),
-        );
-        if let token::Ident(name, false) = self.token.kind {
-            if Ident::new(name, self.token.span).is_raw_guess() {
-                err.span_suggestion(
-                    self.token.span,
-                    "you can escape reserved keywords to use them as identifiers",
-                    format!("r#{}", name),
-                    Applicability::MaybeIncorrect,
-                );
-            }
-        }
-        if let Some(token_descr) = self.token_descr() {
-            err.span_label(self.token.span, format!("expected identifier, found {}", token_descr));
-        } else {
-            err.span_label(self.token.span, "expected identifier");
-            if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
-                err.span_suggestion(
-                    self.token.span,
-                    "remove this comma",
-                    String::new(),
-                    Applicability::MachineApplicable,
-                );
-            }
-        }
-        err
-    }
-
-    pub fn expected_one_of_not_found(
-        &mut self,
-        edible: &[TokenKind],
-        inedible: &[TokenKind],
-    ) -> PResult<'a, bool /* recovered */> {
-        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(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
-            })
-        }
-
-        let mut expected = edible.iter()
-            .map(|x| TokenType::Token(x.clone()))
-            .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
-            .chain(self.expected_tokens.iter().cloned())
-            .collect::<Vec<_>>();
-        expected.sort_by_cached_key(|x| x.to_string());
-        expected.dedup();
-        let expect = tokens_to_string(&expected[..]);
-        let actual = self.this_token_to_string();
-        let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
-            let short_expect = if expected.len() > 6 {
-                format!("{} possible tokens", expected.len())
-            } else {
-                expect.clone()
-            };
-            (format!("expected one of {}, found `{}`", expect, actual),
-                (self.sess.source_map().next_point(self.prev_span),
-                format!("expected one of {} here", short_expect)))
-        } else if expected.is_empty() {
-            (format!("unexpected token: `{}`", actual),
-                (self.prev_span, "unexpected token after this".to_string()))
-        } else {
-            (format!("expected {}, found `{}`", expect, actual),
-                (self.sess.source_map().next_point(self.prev_span),
-                format!("expected {} here", expect)))
-        };
-        self.last_unexpected_token_span = Some(self.token.span);
-        let mut err = self.fatal(&msg_exp);
-        if self.token.is_ident_named(sym::and) {
-            err.span_suggestion_short(
-                self.token.span,
-                "use `&&` instead of `and` for the boolean operator",
-                "&&".to_string(),
-                Applicability::MaybeIncorrect,
-            );
-        }
-        if self.token.is_ident_named(sym::or) {
-            err.span_suggestion_short(
-                self.token.span,
-                "use `||` instead of `or` for the boolean operator",
-                "||".to_string(),
-                Applicability::MaybeIncorrect,
-            );
-        }
-        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_span
-        } else {
-            label_sp
-        };
-        match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
-            TokenType::Token(t) => Some(t.clone()),
-            _ => None,
-        }).collect::<Vec<_>>(), err) {
-            Err(e) => err = e,
-            Ok(recovered) => {
-                return Ok(recovered);
-            }
-        }
-
-        let is_semi_suggestable = expected.iter().any(|t| match t {
-            TokenType::Token(token::Semi) => true, // We expect a `;` here.
-            _ => false,
-        }) && ( // A `;` would be expected before the current keyword.
-            self.token.is_keyword(kw::Break) ||
-            self.token.is_keyword(kw::Continue) ||
-            self.token.is_keyword(kw::For) ||
-            self.token.is_keyword(kw::If) ||
-            self.token.is_keyword(kw::Let) ||
-            self.token.is_keyword(kw::Loop) ||
-            self.token.is_keyword(kw::Match) ||
-            self.token.is_keyword(kw::Return) ||
-            self.token.is_keyword(kw::While)
-        );
-        let sm = self.sess.source_map();
-        match (sm.lookup_line(self.token.span.lo()), sm.lookup_line(sp.lo())) {
-            (Ok(ref a), Ok(ref b)) if a.line != b.line && is_semi_suggestable => {
-                // The spans are in different lines, expected `;` and found `let` or `return`.
-                // High likelihood that it is only a missing `;`.
-                err.span_suggestion_short(
-                    label_sp,
-                    "a semicolon may be missing here",
-                    ";".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-                err.emit();
-                return Ok(true);
-            }
-            (Ok(ref a), Ok(ref b)) if a.line == b.line => {
-                // 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);
-            }
-            _ if self.prev_span == syntax_pos::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, "unexpected token");
-            }
-            _ => {
-                err.span_label(sp, label_exp);
-                err.span_label(self.token.span, "unexpected token");
-            }
-        }
-        self.maybe_annotate_with_ascription(&mut err, false);
-        Err(err)
-    }
-
-    pub fn maybe_annotate_with_ascription(
-        &self,
-        err: &mut DiagnosticBuilder<'_>,
-        maybe_expected_semicolon: bool,
-    ) {
-        if let Some((sp, likely_path)) = self.last_type_ascription {
-            let sm = self.sess.source_map();
-            let next_pos = sm.lookup_char_pos(self.token.span.lo());
-            let op_pos = sm.lookup_char_pos(sp.hi());
-
-            let allow_unstable = self.sess.unstable_features.is_nightly_build();
-
-            if likely_path {
-                err.span_suggestion(
-                    sp,
-                    "maybe write a path separator here",
-                    "::".to_string(),
-                    if allow_unstable {
-                        Applicability::MaybeIncorrect
-                    } else {
-                        Applicability::MachineApplicable
-                    },
-                );
-            } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
-                err.span_suggestion(
-                    sp,
-                    "try using a semicolon",
-                    ";".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            } else if allow_unstable {
-                err.span_label(sp, "tried to parse a type due to this type ascription");
-            } else {
-                err.span_label(sp, "tried to parse a type due to this");
-            }
-            if allow_unstable {
-                // Give extra information about type ascription only if it's a nightly compiler.
-                err.note("`#![feature(type_ascription)]` lets you annotate an expression with a \
-                          type: `<expr>: <type>`");
-                err.note("for more information, see \
-                          https://github.com/rust-lang/rust/issues/23416");
-            }
-        }
-    }
-
-    /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
-    /// passes through any errors encountered. Used for error recovery.
-    crate fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
-        if let Err(ref mut 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 _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
-    ///                                                        ^^ help: remove extra angle brackets
-    /// ```
-    crate fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: TokenKind) {
-        // 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()
-            .map(|args| args.is_angle_bracketed())
-            .unwrap_or(false);
-
-        debug!(
-            "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
-            parsed_angle_bracket_args,
-        );
-        if !parsed_angle_bracket_args {
-            return;
-        }
-
-        // 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;
-        }
-
-        // 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);
-            *t == end
-        }) {
-            // 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 total_num_of_gt = number_of_gt + number_of_shr * 2;
-            self.diagnostic()
-                .struct_span_err(
-                    span,
-                    &format!("unmatched angle bracket{}", pluralise!(total_num_of_gt)),
-                )
-                .span_suggestion(
-                    span,
-                    &format!("remove extra angle bracket{}", pluralise!(total_num_of_gt)),
-                    String::new(),
-                    Applicability::MachineApplicable,
-                )
-                .emit();
-        }
-    }
-
-    /// 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:
-    ///
-    ///           outer_op
-    ///           /   \
-    ///     inner_op   r2
-    ///        /  \
-    ///     l1    r1
-    crate fn check_no_chained_comparison(
-        &mut self,
-        lhs: &Expr,
-        outer_op: &AssocOp,
-    ) -> PResult<'a, Option<P<Expr>>> {
-        debug_assert!(
-            outer_op.is_comparison(),
-            "check_no_chained_comparison: {:?} is not comparison",
-            outer_op,
-        );
-
-        let mk_err_expr = |this: &Self, span| {
-            Ok(Some(this.mk_expr(span, ExprKind::Err, ThinVec::new())))
-        };
-
-        match lhs.kind {
-            ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
-                // Respan to include both operators.
-                let op_span = op.span.to(self.prev_span);
-                let mut err = self.struct_span_err(
-                    op_span,
-                    "chained comparison operators require parentheses",
-                );
-
-                let suggest = |err: &mut DiagnosticBuilder<'_>| {
-                    err.span_suggestion_verbose(
-                        op_span.shrink_to_lo(),
-                        TURBOFISH,
-                        "::".to_string(),
-                        Applicability::MaybeIncorrect,
-                    );
-                };
-
-                if op.node == BinOpKind::Lt &&
-                    *outer_op == AssocOp::Less ||  // Include `<` to provide this recommendation
-                    *outer_op == AssocOp::Greater  // even in a case like the following:
-                {                                  //     Foo<Bar<Baz<Qux, ()>>>
-                    if *outer_op == AssocOp::Less {
-                        let snapshot = self.clone();
-                        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(token::Paren),
-                            token::ModSep,
-                        ].contains(&self.token.kind) {
-                            // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
-                            // parser and bail out.
-                            mem::replace(self, snapshot.clone());
-                        }
-                    }
-                    return if token::ModSep == self.token.kind {
-                        // We have some certainty that this was a bad turbofish at this point.
-                        // `foo< bar >::`
-                        suggest(&mut err);
-
-                        let snapshot = self.clone();
-                        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.
-                                err.emit();
-                                // 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, lhs.span.to(self.prev_span))
-                            }
-                            Err(mut expr_err) => {
-                                expr_err.cancel();
-                                // Not entirely sure now, but we bubble the error up with the
-                                // suggestion.
-                                mem::replace(self, snapshot);
-                                Err(err)
-                            }
-                        }
-                    } else if token::OpenDelim(token::Paren) == self.token.kind {
-                        // We have high certainty that this was a bad turbofish at this point.
-                        // `foo< bar >(`
-                        suggest(&mut err);
-                        // Consume the fn call arguments.
-                        match self.consume_fn_args() {
-                            Err(()) => Err(err),
-                            Ok(()) => {
-                                err.emit();
-                                // 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, lhs.span.to(self.prev_span))
-                            }
-                        }
-                    } else {
-                        // 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);
-                        err.help("or use `(...)` if you meant to specify fn arguments");
-                        // These cases cause too many knock-down errors, bail out (#61329).
-                        Err(err)
-                    };
-                }
-                err.emit();
-            }
-            _ => {}
-        }
-        Ok(None)
-    }
-
-    fn consume_fn_args(&mut self) -> Result<(), ()> {
-        let snapshot = self.clone();
-        self.bump(); // `(`
-
-        // Consume the fn call arguments.
-        let modifiers = [
-            (token::OpenDelim(token::Paren), 1),
-            (token::CloseDelim(token::Paren), -1),
-        ];
-        self.consume_tts(1, &modifiers[..]);
-
-        if self.token.kind == token::Eof {
-            // Not entirely sure that what we consumed were fn arguments, rollback.
-            mem::replace(self, snapshot);
-            Err(())
-        } else {
-            // 99% certain that the suggestion is correct, continue parsing.
-            Ok(())
-        }
-    }
-
-    crate fn maybe_report_ambiguous_plus(
-        &mut self,
-        allow_plus: bool,
-        impl_dyn_multi: bool,
-        ty: &Ty,
-    ) {
-        if !allow_plus && impl_dyn_multi {
-            let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
-            self.struct_span_err(ty.span, "ambiguous `+` in a type")
-                .span_suggestion(
-                    ty.span,
-                    "use parentheses to disambiguate",
-                    sum_with_parens,
-                    Applicability::MachineApplicable,
-                )
-                .emit();
-        }
-    }
-
-    pub(super) fn maybe_recover_from_bad_type_plus(
-        &mut self,
-        allow_plus: bool,
-        ty: &Ty,
-    ) -> PResult<'a, ()> {
-        // Do not add `+` to expected tokens.
-        if !allow_plus || !self.token.is_like_plus() {
-            return Ok(());
-        }
-
-        self.bump(); // `+`
-        let bounds = self.parse_generic_bounds(None)?;
-        let sum_span = ty.span.to(self.prev_span);
-
-        let mut err = struct_span_err!(
-            self.sess.span_diagnostic,
-            sum_span,
-            E0178,
-            "expected a path on the left-hand side of `+`, not `{}`",
-            pprust::ty_to_string(ty)
-        );
-
-        match ty.kind {
-            TyKind::Rptr(ref lifetime, ref mut_ty) => {
-                let sum_with_parens = pprust::to_string(|s| {
-                    s.s.word("&");
-                    s.print_opt_lifetime(lifetime);
-                    s.print_mutability(mut_ty.mutbl);
-                    s.popen();
-                    s.print_type(&mut_ty.ty);
-                    s.print_type_bounds(" +", &bounds);
-                    s.pclose()
-                });
-                err.span_suggestion(
-                    sum_span,
-                    "try adding parentheses",
-                    sum_with_parens,
-                    Applicability::MachineApplicable,
-                );
-            }
-            TyKind::Ptr(..) | TyKind::BareFn(..) => {
-                err.span_label(sum_span, "perhaps you forgot parentheses?");
-            }
-            _ => {
-                err.span_label(sum_span, "expected a path");
-            }
-        }
-        err.emit();
-        Ok(())
-    }
-
-    /// 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.
-    crate fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
-        &mut self,
-        base: P<T>,
-        allow_recovery: bool,
-    ) -> PResult<'a, P<T>> {
-        // Do not add `::` to expected tokens.
-        if allow_recovery && self.token == token::ModSep {
-            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.
-    crate 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::ModSep)?;
-
-        let mut path = ast::Path {
-            segments: Vec::new(),
-            span: DUMMY_SP,
-        };
-        self.parse_path_segments(&mut path.segments, T::PATH_STYLE)?;
-        path.span = ty_span.to(self.prev_span);
-
-        let ty_str = self
-            .span_to_snippet(ty_span)
-            .unwrap_or_else(|_| pprust::ty_to_string(&ty));
-        self.diagnostic()
-            .struct_span_err(path.span, "missing angle brackets in associated item path")
-            .span_suggestion(
-                // This is a best-effort recovery.
-                path.span,
-                "try",
-                format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
-                Applicability::MaybeIncorrect,
-            )
-            .emit();
-
-        let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
-        Ok(P(T::recovered(
-            Some(QSelf {
-                ty,
-                path_span,
-                position: 0,
-            }),
-            path,
-        )))
-    }
-
-    crate fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
-        if self.eat(&token::Semi) {
-            let mut err = self.struct_span_err(self.prev_span, "expected item, found `;`");
-            err.span_suggestion_short(
-                self.prev_span,
-                "remove this semicolon",
-                String::new(),
-                Applicability::MachineApplicable,
-            );
-            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.help(&format!(
-                        "{} declarations are not followed by a semicolon",
-                        name
-                    ));
-                }
-            }
-            err.emit();
-            true
-        } else {
-            false
-        }
-    }
-
-    /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
-    /// closing delimiter.
-    pub fn unexpected_try_recover(
-        &mut self,
-        t: &TokenKind,
-    ) -> PResult<'a, bool /* recovered */> {
-        let token_str = pprust::token_kind_to_string(t);
-        let this_token_str = self.this_token_descr();
-        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.sess.source_map().next_point(self.token.span);
-                (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_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_span, self.token.span),
-            _ => (self.sess.source_map().next_point(self.prev_span), 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.struct_span_err(sp, &msg);
-        let label_exp = format!("expected `{}`", token_str);
-        match self.recover_closing_delimiter(&[t.clone()], err) {
-            Err(e) => err = e,
-            Ok(recovered) => {
-                return Ok(recovered);
-            }
-        }
-        let sm = self.sess.source_map();
-        match (sm.lookup_line(prev_sp.lo()), sm.lookup_line(sp.lo())) {
-            (Ok(ref a), Ok(ref b)) if a.line == b.line => {
-                // 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);
-            }
-            _ => {
-                err.span_label(prev_sp, label_exp);
-                err.span_label(sp, "unexpected token");
-            }
-        }
-        Err(err)
-    }
-
-    crate fn parse_semi_or_incorrect_foreign_fn_body(
-        &mut self,
-        ident: &Ident,
-        extern_sp: Span,
-    ) -> PResult<'a, ()> {
-        if self.token != token::Semi {
-            // This might be an incorrect fn definition (#62109).
-            let parser_snapshot = self.clone();
-            match self.parse_inner_attrs_and_block() {
-                Ok((_, body)) => {
-                    self.struct_span_err(ident.span, "incorrect `fn` inside `extern` block")
-                        .span_label(ident.span, "can't have a body")
-                        .span_label(body.span, "this body is invalid here")
-                        .span_label(
-                            extern_sp,
-                            "`extern` blocks define existing foreign functions and `fn`s \
-                             inside of them cannot have a body")
-                        .help("you might have meant to write a function accessible through ffi, \
-                               which can be done by writing `extern fn` outside of the \
-                               `extern` block")
-                        .note("for more information, visit \
-                               https://doc.rust-lang.org/std/keyword.extern.html")
-                        .emit();
-                }
-                Err(mut err) => {
-                    err.cancel();
-                    mem::replace(self, parser_snapshot);
-                    self.expect(&token::Semi)?;
-                }
-            }
-        } else {
-            self.bump();
-        }
-        Ok(())
-    }
-
-    /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
-    /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
-    crate fn parse_incorrect_await_syntax(
-        &mut self,
-        lo: Span,
-        await_sp: Span,
-    ) -> PResult<'a, (Span, ExprKind)> {
-        if self.token == token::Not {
-            // Handle `await!(<expr>)`.
-            self.expect(&token::Not)?;
-            self.expect(&token::OpenDelim(token::Paren))?;
-            let expr = self.parse_expr()?;
-            self.expect(&token::CloseDelim(token::Paren))?;
-            let sp = self.error_on_incorrect_await(lo, self.prev_span, &expr, false);
-            return Ok((sp, ExprKind::Await(expr)))
-        }
-
-        let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
-        let expr = if self.token == token::OpenDelim(token::Brace) {
-            // Handle `await { <expr> }`.
-            // This needs to be handled separatedly from the next arm to avoid
-            // interpreting `await { <expr> }?` as `<expr>?.await`.
-            self.parse_block_expr(
-                None,
-                self.token.span,
-                BlockCheckMode::Default,
-                ThinVec::new(),
-            )
-        } else {
-            self.parse_expr()
-        }.map_err(|mut err| {
-            err.span_label(await_sp, "while parsing this incorrect await expression");
-            err
-        })?;
-        let sp = self.error_on_incorrect_await(lo, expr.span, &expr, is_question);
-        Ok((sp, ExprKind::Await(expr)))
-    }
-
-    fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
-        let expr_str = self.span_to_snippet(expr.span)
-            .unwrap_or_else(|_| pprust::expr_to_string(&expr));
-        let suggestion = format!("{}.await{}", expr_str, if is_question { "?" } else { "" });
-        let sp = lo.to(hi);
-        let app = match expr.kind {
-            ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
-            _ => Applicability::MachineApplicable,
-        };
-        self.struct_span_err(sp, "incorrect use of `await`")
-            .span_suggestion(sp, "`await` is a postfix operation", suggestion, app)
-            .emit();
-        sp
-    }
-
-    /// If encountering `future.await()`, consumes and emits an error.
-    crate fn recover_from_await_method_call(&mut self) {
-        if self.token == token::OpenDelim(token::Paren) &&
-            self.look_ahead(1, |t| t == &token::CloseDelim(token::Paren))
-        {
-            // future.await()
-            let lo = self.token.span;
-            self.bump(); // (
-            let sp = lo.to(self.token.span);
-            self.bump(); // )
-            self.struct_span_err(sp, "incorrect use of `await`")
-                .span_suggestion(
-                    sp,
-                    "`await` is not a method call, remove the parentheses",
-                    String::new(),
-                    Applicability::MachineApplicable,
-                ).emit()
-        }
-    }
-
-    /// Recovers a situation like `for ( $pat in $expr )`
-    /// and suggest writing `for $pat in $expr` instead.
-    ///
-    /// This should be called before parsing the `$block`.
-    crate fn recover_parens_around_for_head(
-        &mut self,
-        pat: P<Pat>,
-        expr: &Expr,
-        begin_paren: Option<Span>,
-    ) -> P<Pat> {
-        match (&self.token.kind, begin_paren) {
-            (token::CloseDelim(token::Paren), Some(begin_par_sp)) => {
-                self.bump();
-
-                let pat_str = self
-                    // Remove the `(` from the span of the pattern:
-                    .span_to_snippet(pat.span.trim_start(begin_par_sp).unwrap())
-                    .unwrap_or_else(|_| pprust::pat_to_string(&pat));
-
-                self.struct_span_err(self.prev_span, "unexpected closing `)`")
-                    .span_label(begin_par_sp, "opening `(`")
-                    .span_suggestion(
-                        begin_par_sp.to(self.prev_span),
-                        "remove parenthesis in `for` loop",
-                        format!("{} in {}", pat_str, pprust::expr_to_string(&expr)),
-                        // With e.g. `for (x) in y)` this would replace `(x) in y)`
-                        // with `x) in y)` which is syntactically invalid.
-                        // However, this is prevented before we get here.
-                        Applicability::MachineApplicable,
-                    )
-                    .emit();
-
-                // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
-                pat.and_then(|pat| match pat.kind {
-                    PatKind::Paren(pat) => pat,
-                    _ => P(pat),
-                })
-            }
-            _ => pat,
-        }
-    }
-
-    crate fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
-        self.token.is_ident() &&
-            if let ast::ExprKind::Path(..) = node { true } else { false } &&
-            !self.token.is_reserved_ident() &&           // v `foo:bar(baz)`
-            self.look_ahead(1, |t| t == &token::OpenDelim(token::Paren)) ||
-            self.look_ahead(1, |t| t == &token::Lt) &&     // `foo:bar<baz`
-            self.look_ahead(2, |t| t.is_ident()) ||
-            self.look_ahead(1, |t| t == &token::Colon) &&  // `foo:bar:baz`
-            self.look_ahead(2, |t| t.is_ident()) ||
-            self.look_ahead(1, |t| t == &token::ModSep) &&
-            (self.look_ahead(2, |t| t.is_ident()) ||   // `foo:bar::baz`
-             self.look_ahead(2, |t| t == &token::Lt))  // `foo:bar::<baz>`
-    }
-
-    crate fn recover_seq_parse_error(
-        &mut self,
-        delim: token::DelimToken,
-        lo: Span,
-        result: PResult<'a, P<Expr>>,
-    ) -> P<Expr> {
-        match result {
-            Ok(x) => x,
-            Err(mut err) => {
-                err.emit();
-                // Recover from parse error.
-                self.consume_block(delim);
-                self.mk_expr(lo.to(self.prev_span), ExprKind::Err, ThinVec::new())
-            }
-        }
-    }
-
-    crate fn recover_closing_delimiter(
-        &mut self,
-        tokens: &[TokenKind],
-        mut err: DiagnosticBuilder<'a>,
-    ) -> PResult<'a, bool> {
-        let mut pos = None;
-        // We want to use the last closing delim that would apply.
-        for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
-            if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
-                && Some(self.token.span) > unmatched.unclosed_span
-            {
-                pos = Some(i);
-            }
-        }
-        match pos {
-            Some(pos) => {
-                // Recover and assume that the detected unclosed delimiter was meant for
-                // this location. Emit the diagnostic and act as if the delimiter was
-                // present for the parser's sake.
-
-                 // Don't attempt to recover from this unclosed delimiter more than once.
-                let unmatched = self.unclosed_delims.remove(pos);
-                let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
-
-                // We want to suggest the inclusion of the closing delimiter where it makes
-                // the most sense, which is immediately after the last token:
-                //
-                //  {foo(bar {}}
-                //      -      ^
-                //      |      |
-                //      |      help: `)` may belong here
-                //      |
-                //      unclosed delimiter
-                if let Some(sp) = unmatched.unclosed_span {
-                    err.span_label(sp, "unclosed delimiter");
-                }
-                err.span_suggestion_short(
-                    self.sess.source_map().next_point(self.prev_span),
-                    &format!("{} may belong here", delim.to_string()),
-                    delim.to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-                err.emit();
-                self.expected_tokens.clear();  // reduce errors
-                Ok(true)
-            }
-            _ => Err(err),
-        }
-    }
-
-    /// Recovers from `pub` keyword in places where it seems _reasonable_ but isn't valid.
-    crate fn eat_bad_pub(&mut self) {
-        if self.token.is_keyword(kw::Pub) {
-            match self.parse_visibility(false) {
-                Ok(vis) => {
-                    self.diagnostic()
-                        .struct_span_err(vis.span, "unnecessary visibility qualifier")
-                        .span_label(vis.span, "`pub` not permitted here")
-                        .emit();
-                }
-                Err(mut err) => err.emit(),
-            }
-        }
-    }
-
-    /// 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).
-    crate 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.
-    crate 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(token::DelimToken::Brace) => {
-                    brace_depth += 1;
-                    self.bump();
-                    if break_on_block == BlockMode::Break &&
-                       brace_depth == 1 &&
-                       bracket_depth == 0 {
-                        in_block = true;
-                    }
-                }
-                token::OpenDelim(token::DelimToken::Bracket) => {
-                    bracket_depth += 1;
-                    self.bump();
-                }
-                token::CloseDelim(token::DelimToken::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(token::DelimToken::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 =>
-                {
-                    debug!("recover_stmt_ return - Semi");
-                    break;
-                }
-                _ => {
-                    self.bump()
-                }
-            }
-        }
-    }
-
-    crate 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.struct_span_err(self.prev_span, "expected iterable, found keyword `in`")
-                .span_suggestion_short(
-                    in_span.until(self.prev_span),
-                    "remove the duplicated `in`",
-                    String::new(),
-                    Applicability::MachineApplicable,
-                )
-                .emit();
-        }
-    }
-
-    crate fn expected_semi_or_open_brace<T>(&mut self) -> PResult<'a, T> {
-        let token_str = self.this_token_descr();
-        let mut err = self.fatal(&format!("expected `;` or `{{`, found {}", token_str));
-        err.span_label(self.token.span, "expected `;` or `{`");
-        Err(err)
-    }
-
-    crate fn eat_incorrect_doc_comment_for_param_type(&mut self) {
-        if let token::DocComment(_) = self.token.kind {
-            self.struct_span_err(
-                self.token.span,
-                "documentation comments cannot be applied to a function parameter's type",
-            )
-            .span_label(self.token.span, "doc comments are not allowed here")
-            .emit();
-            self.bump();
-        } else if self.token == token::Pound && self.look_ahead(1, |t| {
-            *t == token::OpenDelim(token::Bracket)
-        }) {
-            let lo = self.token.span;
-            // Skip every token until next possible arg.
-            while self.token != token::CloseDelim(token::Bracket) {
-                self.bump();
-            }
-            let sp = lo.to(self.token.span);
-            self.bump();
-            self.struct_span_err(
-                sp,
-                "attributes cannot be applied to a function parameter's type",
-            )
-            .span_label(sp, "attributes are not allowed here")
-            .emit();
-        }
-    }
-
-    crate fn parameter_without_type(
-        &mut self,
-        err: &mut DiagnosticBuilder<'_>,
-        pat: P<ast::Pat>,
-        require_name: bool,
-        is_self_allowed: bool,
-        is_trait_item: 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(token::Paren)
-        }) { // `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",
-                String::from("<identifier>: <type>"),
-                Applicability::HasPlaceholders,
-            );
-            return Some(ident);
-        } else if let PatKind::Ident(_, ident, _) = pat.kind {
-            if require_name && (
-                is_trait_item ||
-                self.token == token::Comma ||
-                self.token == token::Lt ||
-                self.token == token::CloseDelim(token::Paren)
-            ) { // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
-                if is_self_allowed {
-                    err.span_suggestion(
-                        pat.span,
-                        "if this is a `self` type, give it a parameter name",
-                        format!("self: {}", ident),
-                        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(
-                        pat.span,
-                        "if this was a parameter name, give it a type",
-                        format!("{}: TypeName", ident),
-                        Applicability::HasPlaceholders,
-                    );
-                }
-                err.span_suggestion(
-                    pat.span,
-                    "if this is a type, explicitly ignore the parameter name",
-                    format!("_: {}", ident),
-                    Applicability::MachineApplicable,
-                );
-                err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
-
-                // 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
-    }
-
-    crate fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
-        let pat = self.parse_pat(Some("argument name"))?;
-        self.expect(&token::Colon)?;
-        let ty = self.parse_ty()?;
-
-        self.diagnostic()
-            .struct_span_err_with_code(
-                pat.span,
-                "patterns aren't allowed in methods without bodies",
-                DiagnosticId::Error("E0642".into()),
-            )
-            .span_suggestion_short(
-                pat.span,
-                "give this argument a name or use an underscore to ignore it",
-                "_".to_owned(),
-                Applicability::MachineApplicable,
-            )
-            .emit();
-
-        // 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
-        });
-        Ok((pat, ty))
-    }
-
-    crate fn recover_bad_self_param(
-        &mut self,
-        mut param: ast::Param,
-        is_trait_item: bool,
-    ) -> PResult<'a, ast::Param> {
-        let sp = param.pat.span;
-        param.ty.kind = TyKind::Err;
-        let mut err = self.struct_span_err(sp, "unexpected `self` parameter in function");
-        if is_trait_item {
-            err.span_label(sp, "must be the first associated function parameter");
-        } else {
-            err.span_label(sp, "not valid as function parameter");
-            err.note("`self` is only valid as the first parameter of an associated function");
-        }
-        err.emit();
-        Ok(param)
-    }
-
-    crate fn consume_block(&mut self, delim: token::DelimToken) {
-        let mut brace_depth = 0;
-        loop {
-            if self.eat(&token::OpenDelim(delim)) {
-                brace_depth += 1;
-            } else if self.eat(&token::CloseDelim(delim)) {
-                if brace_depth == 0 {
-                    return;
-                } else {
-                    brace_depth -= 1;
-                    continue;
-                }
-            } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
-                return;
-            } else {
-                self.bump();
-            }
-        }
-    }
-
-    crate fn expected_expression_found(&self) -> DiagnosticBuilder<'a> {
-        let (span, msg) = match (&self.token.kind, self.subparser_name) {
-            (&token::Eof, Some(origin)) => {
-                let sp = self.sess.source_map().next_point(self.token.span);
-                (sp, format!("expected expression, found end of {}", origin))
-            }
-            _ => (self.token.span, format!(
-                "expected expression, found {}",
-                self.this_token_descr(),
-            )),
-        };
-        let mut err = self.struct_span_err(span, &msg);
-        let sp = self.sess.source_map().start_point(self.token.span);
-        if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
-            self.sess.expr_parentheses_needed(&mut err, *sp, None);
-        }
-        err.span_label(span, "expected expression");
-        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 unecessary 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
-    /// unecessary 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.
-    crate fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<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);
-            }
-        }
-    }
-}