Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 916 insertions, 0 deletions

diff --git a/third_party/rust/syn/src/pat.rs b/third_party/rust/syn/src/pat.rs
new file mode 100644
index 0000000000..c835d772f0
--- /dev/null
+++ b/third_party/rust/syn/src/pat.rs
@@ -0,0 +1,916 @@
+use super::*;
+use crate::punctuated::Punctuated;
+use proc_macro2::TokenStream;
+
+ast_enum_of_structs! {
+    /// A pattern in a local binding, function signature, match expression, or
+    /// various other places.
+    ///
+    /// # Syntax tree enum
+    ///
+    /// This type is a [syntax tree enum].
+    ///
+    /// [syntax tree enum]: Expr#syntax-tree-enums
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    #[non_exhaustive]
+    pub enum Pat {
+        /// A const block: `const { ... }`.
+        Const(PatConst),
+
+        /// A pattern that binds a new variable: `ref mut binding @ SUBPATTERN`.
+        Ident(PatIdent),
+
+        /// A literal pattern: `0`.
+        Lit(PatLit),
+
+        /// A macro in pattern position.
+        Macro(PatMacro),
+
+        /// A pattern that matches any one of a set of cases.
+        Or(PatOr),
+
+        /// A parenthesized pattern: `(A | B)`.
+        Paren(PatParen),
+
+        /// A path pattern like `Color::Red`, optionally qualified with a
+        /// self-type.
+        ///
+        /// Unqualified path patterns can legally refer to variants, structs,
+        /// constants or associated constants. Qualified path patterns like
+        /// `<A>::B::C` and `<A as Trait>::B::C` can only legally refer to
+        /// associated constants.
+        Path(PatPath),
+
+        /// A range pattern: `1..=2`.
+        Range(PatRange),
+
+        /// A reference pattern: `&mut var`.
+        Reference(PatReference),
+
+        /// The dots in a tuple or slice pattern: `[0, 1, ..]`.
+        Rest(PatRest),
+
+        /// A dynamically sized slice pattern: `[a, b, ref i @ .., y, z]`.
+        Slice(PatSlice),
+
+        /// A struct or struct variant pattern: `Variant { x, y, .. }`.
+        Struct(PatStruct),
+
+        /// A tuple pattern: `(a, b)`.
+        Tuple(PatTuple),
+
+        /// A tuple struct or tuple variant pattern: `Variant(x, y, .., z)`.
+        TupleStruct(PatTupleStruct),
+
+        /// A type ascription pattern: `foo: f64`.
+        Type(PatType),
+
+        /// Tokens in pattern position not interpreted by Syn.
+        Verbatim(TokenStream),
+
+        /// A pattern that matches any value: `_`.
+        Wild(PatWild),
+
+        // For testing exhaustiveness in downstream code, use the following idiom:
+        //
+        //     match pat {
+        //         Pat::Box(pat) => {...}
+        //         Pat::Ident(pat) => {...}
+        //         ...
+        //         Pat::Wild(pat) => {...}
+        //
+        //         #[cfg_attr(test, deny(non_exhaustive_omitted_patterns))]
+        //         _ => { /* some sane fallback */ }
+        //     }
+        //
+        // This way we fail your tests but don't break your library when adding
+        // a variant. You will be notified by a test failure when a variant is
+        // added, so that you can add code to handle it, but your library will
+        // continue to compile and work for downstream users in the interim.
+    }
+}
+
+ast_struct! {
+    /// A pattern that binds a new variable: `ref mut binding @ SUBPATTERN`.
+    ///
+    /// It may also be a unit struct or struct variant (e.g. `None`), or a
+    /// constant; these cannot be distinguished syntactically.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatIdent {
+        pub attrs: Vec<Attribute>,
+        pub by_ref: Option<Token![ref]>,
+        pub mutability: Option<Token![mut]>,
+        pub ident: Ident,
+        pub subpat: Option<(Token![@], Box<Pat>)>,
+    }
+}
+
+ast_struct! {
+    /// A pattern that matches any one of a set of cases.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatOr {
+        pub attrs: Vec<Attribute>,
+        pub leading_vert: Option<Token![|]>,
+        pub cases: Punctuated<Pat, Token![|]>,
+    }
+}
+
+ast_struct! {
+    /// A parenthesized pattern: `(A | B)`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatParen {
+        pub attrs: Vec<Attribute>,
+        pub paren_token: token::Paren,
+        pub pat: Box<Pat>,
+    }
+}
+
+ast_struct! {
+    /// A reference pattern: `&mut var`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatReference {
+        pub attrs: Vec<Attribute>,
+        pub and_token: Token![&],
+        pub mutability: Option<Token![mut]>,
+        pub pat: Box<Pat>,
+    }
+}
+
+ast_struct! {
+    /// The dots in a tuple or slice pattern: `[0, 1, ..]`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatRest {
+        pub attrs: Vec<Attribute>,
+        pub dot2_token: Token![..],
+    }
+}
+
+ast_struct! {
+    /// A dynamically sized slice pattern: `[a, b, ref i @ .., y, z]`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatSlice {
+        pub attrs: Vec<Attribute>,
+        pub bracket_token: token::Bracket,
+        pub elems: Punctuated<Pat, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// A struct or struct variant pattern: `Variant { x, y, .. }`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatStruct {
+        pub attrs: Vec<Attribute>,
+        pub qself: Option<QSelf>,
+        pub path: Path,
+        pub brace_token: token::Brace,
+        pub fields: Punctuated<FieldPat, Token![,]>,
+        pub rest: Option<PatRest>,
+    }
+}
+
+ast_struct! {
+    /// A tuple pattern: `(a, b)`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatTuple {
+        pub attrs: Vec<Attribute>,
+        pub paren_token: token::Paren,
+        pub elems: Punctuated<Pat, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// A tuple struct or tuple variant pattern: `Variant(x, y, .., z)`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatTupleStruct {
+        pub attrs: Vec<Attribute>,
+        pub qself: Option<QSelf>,
+        pub path: Path,
+        pub paren_token: token::Paren,
+        pub elems: Punctuated<Pat, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// A type ascription pattern: `foo: f64`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatType {
+        pub attrs: Vec<Attribute>,
+        pub pat: Box<Pat>,
+        pub colon_token: Token![:],
+        pub ty: Box<Type>,
+    }
+}
+
+ast_struct! {
+    /// A pattern that matches any value: `_`.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct PatWild {
+        pub attrs: Vec<Attribute>,
+        pub underscore_token: Token![_],
+    }
+}
+
+ast_struct! {
+    /// A single field in a struct pattern.
+    ///
+    /// Patterns like the fields of Foo `{ x, ref y, ref mut z }` are treated
+    /// the same as `x: x, y: ref y, z: ref mut z` but there is no colon token.
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
+    pub struct FieldPat {
+        pub attrs: Vec<Attribute>,
+        pub member: Member,
+        pub colon_token: Option<Token![:]>,
+        pub pat: Box<Pat>,
+    }
+}
+
+#[cfg(feature = "parsing")]
+pub(crate) mod parsing {
+    use super::*;
+    use crate::ext::IdentExt as _;
+    use crate::parse::{Parse, ParseBuffer, ParseStream, Result};
+    use crate::path;
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    impl Pat {
+        /// Parse a pattern that does _not_ involve `|` at the top level.
+        ///
+        /// This parser matches the behavior of the `$:pat_param` macro_rules
+        /// matcher, and on editions prior to Rust 2021, the behavior of
+        /// `$:pat`.
+        ///
+        /// In Rust syntax, some examples of where this syntax would occur are
+        /// in the argument pattern of functions and closures. Patterns using
+        /// `|` are not allowed to occur in these positions.
+        ///
+        /// ```compile_fail
+        /// fn f(Some(_) | None: Option<T>) {
+        ///     let _ = |Some(_) | None: Option<T>| {};
+        ///     //       ^^^^^^^^^^^^^^^^^^^^^^^^^??? :(
+        /// }
+        /// ```
+        ///
+        /// ```console
+        /// error: top-level or-patterns are not allowed in function parameters
+        ///  --> src/main.rs:1:6
+        ///   |
+        /// 1 | fn f(Some(_) | None: Option<T>) {
+        ///   |      ^^^^^^^^^^^^^^ help: wrap the pattern in parentheses: `(Some(_) | None)`
+        /// ```
+        pub fn parse_single(input: ParseStream) -> Result<Self> {
+            let begin = input.fork();
+            let lookahead = input.lookahead1();
+            if lookahead.peek(Ident)
+                && (input.peek2(Token![::])
+                    || input.peek2(Token![!])
+                    || input.peek2(token::Brace)
+                    || input.peek2(token::Paren)
+                    || input.peek2(Token![..]))
+                || input.peek(Token![self]) && input.peek2(Token![::])
+                || lookahead.peek(Token![::])
+                || lookahead.peek(Token![<])
+                || input.peek(Token![Self])
+                || input.peek(Token![super])
+                || input.peek(Token![crate])
+            {
+                pat_path_or_macro_or_struct_or_range(input)
+            } else if lookahead.peek(Token![_]) {
+                input.call(pat_wild).map(Pat::Wild)
+            } else if input.peek(Token![box]) {
+                pat_box(begin, input)
+            } else if input.peek(Token![-]) || lookahead.peek(Lit) || lookahead.peek(Token![const])
+            {
+                pat_lit_or_range(input)
+            } else if lookahead.peek(Token![ref])
+                || lookahead.peek(Token![mut])
+                || input.peek(Token![self])
+                || input.peek(Ident)
+            {
+                input.call(pat_ident).map(Pat::Ident)
+            } else if lookahead.peek(Token![&]) {
+                input.call(pat_reference).map(Pat::Reference)
+            } else if lookahead.peek(token::Paren) {
+                input.call(pat_paren_or_tuple)
+            } else if lookahead.peek(token::Bracket) {
+                input.call(pat_slice).map(Pat::Slice)
+            } else if lookahead.peek(Token![..]) && !input.peek(Token![...]) {
+                pat_range_half_open(input)
+            } else if lookahead.peek(Token![const]) {
+                input.call(pat_const).map(Pat::Verbatim)
+            } else {
+                Err(lookahead.error())
+            }
+        }
+
+        /// Parse a pattern, possibly involving `|`, but not a leading `|`.
+        pub fn parse_multi(input: ParseStream) -> Result<Self> {
+            multi_pat_impl(input, None)
+        }
+
+        /// Parse a pattern, possibly involving `|`, possibly including a
+        /// leading `|`.
+        ///
+        /// This parser matches the behavior of the Rust 2021 edition's `$:pat`
+        /// macro_rules matcher.
+        ///
+        /// In Rust syntax, an example of where this syntax would occur is in
+        /// the pattern of a `match` arm, where the language permits an optional
+        /// leading `|`, although it is not idiomatic to write one there in
+        /// handwritten code.
+        ///
+        /// ```
+        /// # let wat = None;
+        /// match wat {
+        ///     | None | Some(false) => {}
+        ///     | Some(true) => {}
+        /// }
+        /// ```
+        ///
+        /// The compiler accepts it only to facilitate some situations in
+        /// macro-generated code where a macro author might need to write:
+        ///
+        /// ```
+        /// # macro_rules! doc {
+        /// #     ($value:expr, ($($conditions1:pat),*), ($($conditions2:pat),*), $then:expr) => {
+        /// match $value {
+        ///     $(| $conditions1)* $(| $conditions2)* => $then
+        /// }
+        /// #     };
+        /// # }
+        /// #
+        /// # doc!(true, (true), (false), {});
+        /// # doc!(true, (), (true, false), {});
+        /// # doc!(true, (true, false), (), {});
+        /// ```
+        ///
+        /// Expressing the same thing correctly in the case that either one (but
+        /// not both) of `$conditions1` and `$conditions2` might be empty,
+        /// without leading `|`, is complex.
+        ///
+        /// Use [`Pat::parse_multi`] instead if you are not intending to support
+        /// macro-generated macro input.
+        pub fn parse_multi_with_leading_vert(input: ParseStream) -> Result<Self> {
+            let leading_vert: Option<Token![|]> = input.parse()?;
+            multi_pat_impl(input, leading_vert)
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
+    impl Parse for PatType {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(PatType {
+                attrs: Vec::new(),
+                pat: Box::new(Pat::parse_single(input)?),
+                colon_token: input.parse()?,
+                ty: input.parse()?,
+            })
+        }
+    }
+
+    fn multi_pat_impl(input: ParseStream, leading_vert: Option<Token![|]>) -> Result<Pat> {
+        let mut pat = Pat::parse_single(input)?;
+        if leading_vert.is_some()
+            || input.peek(Token![|]) && !input.peek(Token![||]) && !input.peek(Token![|=])
+        {
+            let mut cases = Punctuated::new();
+            cases.push_value(pat);
+            while input.peek(Token![|]) && !input.peek(Token![||]) && !input.peek(Token![|=]) {
+                let punct = input.parse()?;
+                cases.push_punct(punct);
+                let pat = Pat::parse_single(input)?;
+                cases.push_value(pat);
+            }
+            pat = Pat::Or(PatOr {
+                attrs: Vec::new(),
+                leading_vert,
+                cases,
+            });
+        }
+        Ok(pat)
+    }
+
+    fn pat_path_or_macro_or_struct_or_range(input: ParseStream) -> Result<Pat> {
+        let (qself, path) = path::parsing::qpath(input, true)?;
+
+        if qself.is_none()
+            && input.peek(Token![!])
+            && !input.peek(Token![!=])
+            && path.is_mod_style()
+        {
+            let bang_token: Token![!] = input.parse()?;
+            let (delimiter, tokens) = mac::parse_delimiter(input)?;
+            return Ok(Pat::Macro(ExprMacro {
+                attrs: Vec::new(),
+                mac: Macro {
+                    path,
+                    bang_token,
+                    delimiter,
+                    tokens,
+                },
+            }));
+        }
+
+        if input.peek(token::Brace) {
+            pat_struct(input, qself, path).map(Pat::Struct)
+        } else if input.peek(token::Paren) {
+            pat_tuple_struct(input, qself, path).map(Pat::TupleStruct)
+        } else if input.peek(Token![..]) {
+            pat_range(input, qself, path)
+        } else {
+            Ok(Pat::Path(ExprPath {
+                attrs: Vec::new(),
+                qself,
+                path,
+            }))
+        }
+    }
+
+    fn pat_wild(input: ParseStream) -> Result<PatWild> {
+        Ok(PatWild {
+            attrs: Vec::new(),
+            underscore_token: input.parse()?,
+        })
+    }
+
+    fn pat_box(begin: ParseBuffer, input: ParseStream) -> Result<Pat> {
+        input.parse::<Token![box]>()?;
+        Pat::parse_single(input)?;
+        Ok(Pat::Verbatim(verbatim::between(&begin, input)))
+    }
+
+    fn pat_ident(input: ParseStream) -> Result<PatIdent> {
+        Ok(PatIdent {
+            attrs: Vec::new(),
+            by_ref: input.parse()?,
+            mutability: input.parse()?,
+            ident: input.call(Ident::parse_any)?,
+            subpat: {
+                if input.peek(Token![@]) {
+                    let at_token: Token![@] = input.parse()?;
+                    let subpat = Pat::parse_single(input)?;
+                    Some((at_token, Box::new(subpat)))
+                } else {
+                    None
+                }
+            },
+        })
+    }
+
+    fn pat_tuple_struct(
+        input: ParseStream,
+        qself: Option<QSelf>,
+        path: Path,
+    ) -> Result<PatTupleStruct> {
+        let content;
+        let paren_token = parenthesized!(content in input);
+
+        let mut elems = Punctuated::new();
+        while !content.is_empty() {
+            let value = Pat::parse_multi_with_leading_vert(&content)?;
+            elems.push_value(value);
+            if content.is_empty() {
+                break;
+            }
+            let punct = content.parse()?;
+            elems.push_punct(punct);
+        }
+
+        Ok(PatTupleStruct {
+            attrs: Vec::new(),
+            qself,
+            path,
+            paren_token,
+            elems,
+        })
+    }
+
+    fn pat_struct(input: ParseStream, qself: Option<QSelf>, path: Path) -> Result<PatStruct> {
+        let content;
+        let brace_token = braced!(content in input);
+
+        let mut fields = Punctuated::new();
+        let mut rest = None;
+        while !content.is_empty() {
+            let attrs = content.call(Attribute::parse_outer)?;
+            if content.peek(Token![..]) {
+                rest = Some(PatRest {
+                    attrs,
+                    dot2_token: content.parse()?,
+                });
+                break;
+            }
+            let mut value = content.call(field_pat)?;
+            value.attrs = attrs;
+            fields.push_value(value);
+            if content.is_empty() {
+                break;
+            }
+            let punct: Token![,] = content.parse()?;
+            fields.push_punct(punct);
+        }
+
+        Ok(PatStruct {
+            attrs: Vec::new(),
+            qself,
+            path,
+            brace_token,
+            fields,
+            rest,
+        })
+    }
+
+    fn field_pat(input: ParseStream) -> Result<FieldPat> {
+        let begin = input.fork();
+        let boxed: Option<Token![box]> = input.parse()?;
+        let by_ref: Option<Token![ref]> = input.parse()?;
+        let mutability: Option<Token![mut]> = input.parse()?;
+
+        let member = if boxed.is_some() || by_ref.is_some() || mutability.is_some() {
+            input.parse().map(Member::Named)
+        } else {
+            input.parse()
+        }?;
+
+        if boxed.is_none() && by_ref.is_none() && mutability.is_none() && input.peek(Token![:])
+            || !member.is_named()
+        {
+            return Ok(FieldPat {
+                attrs: Vec::new(),
+                member,
+                colon_token: Some(input.parse()?),
+                pat: Box::new(Pat::parse_multi_with_leading_vert(input)?),
+            });
+        }
+
+        let ident = match member {
+            Member::Named(ident) => ident,
+            Member::Unnamed(_) => unreachable!(),
+        };
+
+        let pat = if boxed.is_some() {
+            Pat::Verbatim(verbatim::between(&begin, input))
+        } else {
+            Pat::Ident(PatIdent {
+                attrs: Vec::new(),
+                by_ref,
+                mutability,
+                ident: ident.clone(),
+                subpat: None,
+            })
+        };
+
+        Ok(FieldPat {
+            attrs: Vec::new(),
+            member: Member::Named(ident),
+            colon_token: None,
+            pat: Box::new(pat),
+        })
+    }
+
+    fn pat_range(input: ParseStream, qself: Option<QSelf>, path: Path) -> Result<Pat> {
+        let limits = RangeLimits::parse_obsolete(input)?;
+        let end = input.call(pat_range_bound)?;
+        if let (RangeLimits::Closed(_), None) = (&limits, &end) {
+            return Err(input.error("expected range upper bound"));
+        }
+        Ok(Pat::Range(ExprRange {
+            attrs: Vec::new(),
+            start: Some(Box::new(Expr::Path(ExprPath {
+                attrs: Vec::new(),
+                qself,
+                path,
+            }))),
+            limits,
+            end: end.map(PatRangeBound::into_expr),
+        }))
+    }
+
+    fn pat_range_half_open(input: ParseStream) -> Result<Pat> {
+        let limits: RangeLimits = input.parse()?;
+        let end = input.call(pat_range_bound)?;
+        if end.is_some() {
+            Ok(Pat::Range(ExprRange {
+                attrs: Vec::new(),
+                start: None,
+                limits,
+                end: end.map(PatRangeBound::into_expr),
+            }))
+        } else {
+            match limits {
+                RangeLimits::HalfOpen(dot2_token) => Ok(Pat::Rest(PatRest {
+                    attrs: Vec::new(),
+                    dot2_token,
+                })),
+                RangeLimits::Closed(_) => Err(input.error("expected range upper bound")),
+            }
+        }
+    }
+
+    fn pat_paren_or_tuple(input: ParseStream) -> Result<Pat> {
+        let content;
+        let paren_token = parenthesized!(content in input);
+
+        let mut elems = Punctuated::new();
+        while !content.is_empty() {
+            let value = Pat::parse_multi_with_leading_vert(&content)?;
+            if content.is_empty() {
+                if elems.is_empty() && !matches!(value, Pat::Rest(_)) {
+                    return Ok(Pat::Paren(PatParen {
+                        attrs: Vec::new(),
+                        paren_token,
+                        pat: Box::new(value),
+                    }));
+                }
+                elems.push_value(value);
+                break;
+            }
+            elems.push_value(value);
+            let punct = content.parse()?;
+            elems.push_punct(punct);
+        }
+
+        Ok(Pat::Tuple(PatTuple {
+            attrs: Vec::new(),
+            paren_token,
+            elems,
+        }))
+    }
+
+    fn pat_reference(input: ParseStream) -> Result<PatReference> {
+        Ok(PatReference {
+            attrs: Vec::new(),
+            and_token: input.parse()?,
+            mutability: input.parse()?,
+            pat: Box::new(Pat::parse_single(input)?),
+        })
+    }
+
+    fn pat_lit_or_range(input: ParseStream) -> Result<Pat> {
+        let start = input.call(pat_range_bound)?.unwrap();
+        if input.peek(Token![..]) {
+            let limits = RangeLimits::parse_obsolete(input)?;
+            let end = input.call(pat_range_bound)?;
+            if let (RangeLimits::Closed(_), None) = (&limits, &end) {
+                return Err(input.error("expected range upper bound"));
+            }
+            Ok(Pat::Range(ExprRange {
+                attrs: Vec::new(),
+                start: Some(start.into_expr()),
+                limits,
+                end: end.map(PatRangeBound::into_expr),
+            }))
+        } else {
+            Ok(start.into_pat())
+        }
+    }
+
+    // Patterns that can appear on either side of a range pattern.
+    enum PatRangeBound {
+        Const(ExprConst),
+        Lit(ExprLit),
+        Path(ExprPath),
+    }
+
+    impl PatRangeBound {
+        fn into_expr(self) -> Box<Expr> {
+            Box::new(match self {
+                PatRangeBound::Const(pat) => Expr::Const(pat),
+                PatRangeBound::Lit(pat) => Expr::Lit(pat),
+                PatRangeBound::Path(pat) => Expr::Path(pat),
+            })
+        }
+
+        fn into_pat(self) -> Pat {
+            match self {
+                PatRangeBound::Const(pat) => Pat::Const(pat),
+                PatRangeBound::Lit(pat) => Pat::Lit(pat),
+                PatRangeBound::Path(pat) => Pat::Path(pat),
+            }
+        }
+    }
+
+    fn pat_range_bound(input: ParseStream) -> Result<Option<PatRangeBound>> {
+        if input.is_empty()
+            || input.peek(Token![|])
+            || input.peek(Token![=])
+            || input.peek(Token![:]) && !input.peek(Token![::])
+            || input.peek(Token![,])
+            || input.peek(Token![;])
+            || input.peek(Token![if])
+        {
+            return Ok(None);
+        }
+
+        let lookahead = input.lookahead1();
+        let expr = if lookahead.peek(Lit) {
+            PatRangeBound::Lit(input.parse()?)
+        } else if lookahead.peek(Ident)
+            || lookahead.peek(Token![::])
+            || lookahead.peek(Token![<])
+            || lookahead.peek(Token![self])
+            || lookahead.peek(Token![Self])
+            || lookahead.peek(Token![super])
+            || lookahead.peek(Token![crate])
+        {
+            PatRangeBound::Path(input.parse()?)
+        } else if lookahead.peek(Token![const]) {
+            PatRangeBound::Const(input.parse()?)
+        } else {
+            return Err(lookahead.error());
+        };
+
+        Ok(Some(expr))
+    }
+
+    fn pat_slice(input: ParseStream) -> Result<PatSlice> {
+        let content;
+        let bracket_token = bracketed!(content in input);
+
+        let mut elems = Punctuated::new();
+        while !content.is_empty() {
+            let value = Pat::parse_multi_with_leading_vert(&content)?;
+            match value {
+                Pat::Range(pat) if pat.start.is_none() || pat.end.is_none() => {
+                    let (start, end) = match pat.limits {
+                        RangeLimits::HalfOpen(dot_dot) => (dot_dot.spans[0], dot_dot.spans[1]),
+                        RangeLimits::Closed(dot_dot_eq) => {
+                            (dot_dot_eq.spans[0], dot_dot_eq.spans[2])
+                        }
+                    };
+                    let msg = "range pattern is not allowed unparenthesized inside slice pattern";
+                    return Err(error::new2(start, end, msg));
+                }
+                _ => {}
+            }
+            elems.push_value(value);
+            if content.is_empty() {
+                break;
+            }
+            let punct = content.parse()?;
+            elems.push_punct(punct);
+        }
+
+        Ok(PatSlice {
+            attrs: Vec::new(),
+            bracket_token,
+            elems,
+        })
+    }
+
+    fn pat_const(input: ParseStream) -> Result<TokenStream> {
+        let begin = input.fork();
+        input.parse::<Token![const]>()?;
+
+        let content;
+        braced!(content in input);
+        content.call(Attribute::parse_inner)?;
+        content.call(Block::parse_within)?;
+
+        Ok(verbatim::between(&begin, input))
+    }
+}
+
+#[cfg(feature = "printing")]
+mod printing {
+    use super::*;
+    use crate::attr::FilterAttrs;
+    use proc_macro2::TokenStream;
+    use quote::{ToTokens, TokenStreamExt};
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatIdent {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.by_ref.to_tokens(tokens);
+            self.mutability.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            if let Some((at_token, subpat)) = &self.subpat {
+                at_token.to_tokens(tokens);
+                subpat.to_tokens(tokens);
+            }
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatOr {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.leading_vert.to_tokens(tokens);
+            self.cases.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatParen {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.paren_token.surround(tokens, |tokens| {
+                self.pat.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatReference {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.and_token.to_tokens(tokens);
+            self.mutability.to_tokens(tokens);
+            self.pat.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatRest {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.dot2_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatSlice {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.bracket_token.surround(tokens, |tokens| {
+                self.elems.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatStruct {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            path::printing::print_path(tokens, &self.qself, &self.path);
+            self.brace_token.surround(tokens, |tokens| {
+                self.fields.to_tokens(tokens);
+                // NOTE: We need a comma before the dot2 token if it is present.
+                if !self.fields.empty_or_trailing() && self.rest.is_some() {
+                    <Token![,]>::default().to_tokens(tokens);
+                }
+                self.rest.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatTuple {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.paren_token.surround(tokens, |tokens| {
+                self.elems.to_tokens(tokens);
+                // If there is only one element, a trailing comma is needed to
+                // distinguish PatTuple from PatParen, unless this is `(..)`
+                // which is a tuple pattern even without comma.
+                if self.elems.len() == 1
+                    && !self.elems.trailing_punct()
+                    && !matches!(self.elems[0], Pat::Rest { .. })
+                {
+                    <Token![,]>::default().to_tokens(tokens);
+                }
+            });
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatTupleStruct {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            path::printing::print_path(tokens, &self.qself, &self.path);
+            self.paren_token.surround(tokens, |tokens| {
+                self.elems.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatType {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.pat.to_tokens(tokens);
+            self.colon_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for PatWild {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.underscore_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
+    impl ToTokens for FieldPat {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            if let Some(colon_token) = &self.colon_token {
+                self.member.to_tokens(tokens);
+                colon_token.to_tokens(tokens);
+            }
+            self.pat.to_tokens(tokens);
+        }
+    }
+}