Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 3492 insertions, 0 deletions

diff --git a/rust/syn/item.rs b/rust/syn/item.rs
new file mode 100644
index 000000000..1ab10cf21
--- /dev/null
+++ b/rust/syn/item.rs
@@ -0,0 +1,3492 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::attr::Attribute;
+use crate::data::{Fields, FieldsNamed, Variant};
+use crate::derive::{Data, DataEnum, DataStruct, DataUnion, DeriveInput};
+use crate::expr::Expr;
+use crate::generics::{Generics, TypeParamBound};
+use crate::ident::Ident;
+use crate::lifetime::Lifetime;
+use crate::mac::Macro;
+use crate::pat::{Pat, PatType};
+use crate::path::Path;
+use crate::punctuated::Punctuated;
+use crate::restriction::Visibility;
+use crate::stmt::Block;
+use crate::token;
+use crate::ty::{Abi, ReturnType, Type};
+use proc_macro2::TokenStream;
+#[cfg(feature = "parsing")]
+use std::mem;
+
+ast_enum_of_structs! {
+    /// Things that can appear directly inside of a module or scope.
+    ///
+    /// # Syntax tree enum
+    ///
+    /// This type is a [syntax tree enum].
+    ///
+    /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    #[non_exhaustive]
+    pub enum Item {
+        /// A constant item: `const MAX: u16 = 65535`.
+        Const(ItemConst),
+
+        /// An enum definition: `enum Foo<A, B> { A(A), B(B) }`.
+        Enum(ItemEnum),
+
+        /// An `extern crate` item: `extern crate serde`.
+        ExternCrate(ItemExternCrate),
+
+        /// A free-standing function: `fn process(n: usize) -> Result<()> { ...
+        /// }`.
+        Fn(ItemFn),
+
+        /// A block of foreign items: `extern "C" { ... }`.
+        ForeignMod(ItemForeignMod),
+
+        /// An impl block providing trait or associated items: `impl<A> Trait
+        /// for Data<A> { ... }`.
+        Impl(ItemImpl),
+
+        /// A macro invocation, which includes `macro_rules!` definitions.
+        Macro(ItemMacro),
+
+        /// A module or module declaration: `mod m` or `mod m { ... }`.
+        Mod(ItemMod),
+
+        /// A static item: `static BIKE: Shed = Shed(42)`.
+        Static(ItemStatic),
+
+        /// A struct definition: `struct Foo<A> { x: A }`.
+        Struct(ItemStruct),
+
+        /// A trait definition: `pub trait Iterator { ... }`.
+        Trait(ItemTrait),
+
+        /// A trait alias: `pub trait SharableIterator = Iterator + Sync`.
+        TraitAlias(ItemTraitAlias),
+
+        /// A type alias: `type Result<T> = std::result::Result<T, MyError>`.
+        Type(ItemType),
+
+        /// A union definition: `union Foo<A, B> { x: A, y: B }`.
+        Union(ItemUnion),
+
+        /// A use declaration: `use std::collections::HashMap`.
+        Use(ItemUse),
+
+        /// Tokens forming an item not interpreted by Syn.
+        Verbatim(TokenStream),
+
+        // For testing exhaustiveness in downstream code, use the following idiom:
+        //
+        //     match item {
+        //         #![cfg_attr(test, deny(non_exhaustive_omitted_patterns))]
+        //
+        //         Item::Const(item) => {...}
+        //         Item::Enum(item) => {...}
+        //         ...
+        //         Item::Verbatim(item) => {...}
+        //
+        //         _ => { /* 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 constant item: `const MAX: u16 = 65535`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemConst {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub const_token: Token![const],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub colon_token: Token![:],
+        pub ty: Box<Type>,
+        pub eq_token: Token![=],
+        pub expr: Box<Expr>,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// An enum definition: `enum Foo<A, B> { A(A), B(B) }`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemEnum {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub enum_token: Token![enum],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub brace_token: token::Brace,
+        pub variants: Punctuated<Variant, Token![,]>,
+    }
+}
+
+ast_struct! {
+    /// An `extern crate` item: `extern crate serde`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemExternCrate {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub extern_token: Token![extern],
+        pub crate_token: Token![crate],
+        pub ident: Ident,
+        pub rename: Option<(Token![as], Ident)>,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A free-standing function: `fn process(n: usize) -> Result<()> { ... }`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemFn {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub sig: Signature,
+        pub block: Box<Block>,
+    }
+}
+
+ast_struct! {
+    /// A block of foreign items: `extern "C" { ... }`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemForeignMod {
+        pub attrs: Vec<Attribute>,
+        pub unsafety: Option<Token![unsafe]>,
+        pub abi: Abi,
+        pub brace_token: token::Brace,
+        pub items: Vec<ForeignItem>,
+    }
+}
+
+ast_struct! {
+    /// An impl block providing trait or associated items: `impl<A> Trait
+    /// for Data<A> { ... }`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemImpl {
+        pub attrs: Vec<Attribute>,
+        pub defaultness: Option<Token![default]>,
+        pub unsafety: Option<Token![unsafe]>,
+        pub impl_token: Token![impl],
+        pub generics: Generics,
+        /// Trait this impl implements.
+        pub trait_: Option<(Option<Token![!]>, Path, Token![for])>,
+        /// The Self type of the impl.
+        pub self_ty: Box<Type>,
+        pub brace_token: token::Brace,
+        pub items: Vec<ImplItem>,
+    }
+}
+
+ast_struct! {
+    /// A macro invocation, which includes `macro_rules!` definitions.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemMacro {
+        pub attrs: Vec<Attribute>,
+        /// The `example` in `macro_rules! example { ... }`.
+        pub ident: Option<Ident>,
+        pub mac: Macro,
+        pub semi_token: Option<Token![;]>,
+    }
+}
+
+ast_struct! {
+    /// A module or module declaration: `mod m` or `mod m { ... }`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemMod {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub unsafety: Option<Token![unsafe]>,
+        pub mod_token: Token![mod],
+        pub ident: Ident,
+        pub content: Option<(token::Brace, Vec<Item>)>,
+        pub semi: Option<Token![;]>,
+    }
+}
+
+ast_struct! {
+    /// A static item: `static BIKE: Shed = Shed(42)`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemStatic {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub static_token: Token![static],
+        pub mutability: StaticMutability,
+        pub ident: Ident,
+        pub colon_token: Token![:],
+        pub ty: Box<Type>,
+        pub eq_token: Token![=],
+        pub expr: Box<Expr>,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A struct definition: `struct Foo<A> { x: A }`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemStruct {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub struct_token: Token![struct],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub fields: Fields,
+        pub semi_token: Option<Token![;]>,
+    }
+}
+
+ast_struct! {
+    /// A trait definition: `pub trait Iterator { ... }`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemTrait {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub unsafety: Option<Token![unsafe]>,
+        pub auto_token: Option<Token![auto]>,
+        pub restriction: Option<ImplRestriction>,
+        pub trait_token: Token![trait],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub colon_token: Option<Token![:]>,
+        pub supertraits: Punctuated<TypeParamBound, Token![+]>,
+        pub brace_token: token::Brace,
+        pub items: Vec<TraitItem>,
+    }
+}
+
+ast_struct! {
+    /// A trait alias: `pub trait SharableIterator = Iterator + Sync`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemTraitAlias {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub trait_token: Token![trait],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub eq_token: Token![=],
+        pub bounds: Punctuated<TypeParamBound, Token![+]>,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A type alias: `type Result<T> = std::result::Result<T, MyError>`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemType {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub type_token: Token![type],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub eq_token: Token![=],
+        pub ty: Box<Type>,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A union definition: `union Foo<A, B> { x: A, y: B }`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemUnion {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub union_token: Token![union],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub fields: FieldsNamed,
+    }
+}
+
+ast_struct! {
+    /// A use declaration: `use std::collections::HashMap`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ItemUse {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub use_token: Token![use],
+        pub leading_colon: Option<Token![::]>,
+        pub tree: UseTree,
+        pub semi_token: Token![;],
+    }
+}
+
+impl Item {
+    #[cfg(feature = "parsing")]
+    pub(crate) fn replace_attrs(&mut self, new: Vec<Attribute>) -> Vec<Attribute> {
+        match self {
+            Item::Const(ItemConst { attrs, .. })
+            | Item::Enum(ItemEnum { attrs, .. })
+            | Item::ExternCrate(ItemExternCrate { attrs, .. })
+            | Item::Fn(ItemFn { attrs, .. })
+            | Item::ForeignMod(ItemForeignMod { attrs, .. })
+            | Item::Impl(ItemImpl { attrs, .. })
+            | Item::Macro(ItemMacro { attrs, .. })
+            | Item::Mod(ItemMod { attrs, .. })
+            | Item::Static(ItemStatic { attrs, .. })
+            | Item::Struct(ItemStruct { attrs, .. })
+            | Item::Trait(ItemTrait { attrs, .. })
+            | Item::TraitAlias(ItemTraitAlias { attrs, .. })
+            | Item::Type(ItemType { attrs, .. })
+            | Item::Union(ItemUnion { attrs, .. })
+            | Item::Use(ItemUse { attrs, .. }) => mem::replace(attrs, new),
+            Item::Verbatim(_) => Vec::new(),
+        }
+    }
+}
+
+impl From<DeriveInput> for Item {
+    fn from(input: DeriveInput) -> Item {
+        match input.data {
+            Data::Struct(data) => Item::Struct(ItemStruct {
+                attrs: input.attrs,
+                vis: input.vis,
+                struct_token: data.struct_token,
+                ident: input.ident,
+                generics: input.generics,
+                fields: data.fields,
+                semi_token: data.semi_token,
+            }),
+            Data::Enum(data) => Item::Enum(ItemEnum {
+                attrs: input.attrs,
+                vis: input.vis,
+                enum_token: data.enum_token,
+                ident: input.ident,
+                generics: input.generics,
+                brace_token: data.brace_token,
+                variants: data.variants,
+            }),
+            Data::Union(data) => Item::Union(ItemUnion {
+                attrs: input.attrs,
+                vis: input.vis,
+                union_token: data.union_token,
+                ident: input.ident,
+                generics: input.generics,
+                fields: data.fields,
+            }),
+        }
+    }
+}
+
+impl From<ItemStruct> for DeriveInput {
+    fn from(input: ItemStruct) -> DeriveInput {
+        DeriveInput {
+            attrs: input.attrs,
+            vis: input.vis,
+            ident: input.ident,
+            generics: input.generics,
+            data: Data::Struct(DataStruct {
+                struct_token: input.struct_token,
+                fields: input.fields,
+                semi_token: input.semi_token,
+            }),
+        }
+    }
+}
+
+impl From<ItemEnum> for DeriveInput {
+    fn from(input: ItemEnum) -> DeriveInput {
+        DeriveInput {
+            attrs: input.attrs,
+            vis: input.vis,
+            ident: input.ident,
+            generics: input.generics,
+            data: Data::Enum(DataEnum {
+                enum_token: input.enum_token,
+                brace_token: input.brace_token,
+                variants: input.variants,
+            }),
+        }
+    }
+}
+
+impl From<ItemUnion> for DeriveInput {
+    fn from(input: ItemUnion) -> DeriveInput {
+        DeriveInput {
+            attrs: input.attrs,
+            vis: input.vis,
+            ident: input.ident,
+            generics: input.generics,
+            data: Data::Union(DataUnion {
+                union_token: input.union_token,
+                fields: input.fields,
+            }),
+        }
+    }
+}
+
+ast_enum_of_structs! {
+    /// A suffix of an import tree in a `use` item: `Type as Renamed` or `*`.
+    ///
+    /// # Syntax tree enum
+    ///
+    /// This type is a [syntax tree enum].
+    ///
+    /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub enum UseTree {
+        /// A path prefix of imports in a `use` item: `std::...`.
+        Path(UsePath),
+
+        /// An identifier imported by a `use` item: `HashMap`.
+        Name(UseName),
+
+        /// An renamed identifier imported by a `use` item: `HashMap as Map`.
+        Rename(UseRename),
+
+        /// A glob import in a `use` item: `*`.
+        Glob(UseGlob),
+
+        /// A braced group of imports in a `use` item: `{A, B, C}`.
+        Group(UseGroup),
+    }
+}
+
+ast_struct! {
+    /// A path prefix of imports in a `use` item: `std::...`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct UsePath {
+        pub ident: Ident,
+        pub colon2_token: Token![::],
+        pub tree: Box<UseTree>,
+    }
+}
+
+ast_struct! {
+    /// An identifier imported by a `use` item: `HashMap`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct UseName {
+        pub ident: Ident,
+    }
+}
+
+ast_struct! {
+    /// An renamed identifier imported by a `use` item: `HashMap as Map`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct UseRename {
+        pub ident: Ident,
+        pub as_token: Token![as],
+        pub rename: Ident,
+    }
+}
+
+ast_struct! {
+    /// A glob import in a `use` item: `*`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct UseGlob {
+        pub star_token: Token![*],
+    }
+}
+
+ast_struct! {
+    /// A braced group of imports in a `use` item: `{A, B, C}`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct UseGroup {
+        pub brace_token: token::Brace,
+        pub items: Punctuated<UseTree, Token![,]>,
+    }
+}
+
+ast_enum_of_structs! {
+    /// An item within an `extern` block.
+    ///
+    /// # Syntax tree enum
+    ///
+    /// This type is a [syntax tree enum].
+    ///
+    /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    #[non_exhaustive]
+    pub enum ForeignItem {
+        /// A foreign function in an `extern` block.
+        Fn(ForeignItemFn),
+
+        /// A foreign static item in an `extern` block: `static ext: u8`.
+        Static(ForeignItemStatic),
+
+        /// A foreign type in an `extern` block: `type void`.
+        Type(ForeignItemType),
+
+        /// A macro invocation within an extern block.
+        Macro(ForeignItemMacro),
+
+        /// Tokens in an `extern` block not interpreted by Syn.
+        Verbatim(TokenStream),
+
+        // For testing exhaustiveness in downstream code, use the following idiom:
+        //
+        //     match item {
+        //         #![cfg_attr(test, deny(non_exhaustive_omitted_patterns))]
+        //
+        //         ForeignItem::Fn(item) => {...}
+        //         ForeignItem::Static(item) => {...}
+        //         ...
+        //         ForeignItem::Verbatim(item) => {...}
+        //
+        //         _ => { /* 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 foreign function in an `extern` block.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ForeignItemFn {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub sig: Signature,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A foreign static item in an `extern` block: `static ext: u8`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ForeignItemStatic {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub static_token: Token![static],
+        pub mutability: StaticMutability,
+        pub ident: Ident,
+        pub colon_token: Token![:],
+        pub ty: Box<Type>,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A foreign type in an `extern` block: `type void`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ForeignItemType {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub type_token: Token![type],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A macro invocation within an extern block.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ForeignItemMacro {
+        pub attrs: Vec<Attribute>,
+        pub mac: Macro,
+        pub semi_token: Option<Token![;]>,
+    }
+}
+
+ast_enum_of_structs! {
+    /// An item declaration within the definition of a trait.
+    ///
+    /// # Syntax tree enum
+    ///
+    /// This type is a [syntax tree enum].
+    ///
+    /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    #[non_exhaustive]
+    pub enum TraitItem {
+        /// An associated constant within the definition of a trait.
+        Const(TraitItemConst),
+
+        /// An associated function within the definition of a trait.
+        Fn(TraitItemFn),
+
+        /// An associated type within the definition of a trait.
+        Type(TraitItemType),
+
+        /// A macro invocation within the definition of a trait.
+        Macro(TraitItemMacro),
+
+        /// Tokens within the definition of a trait not interpreted by Syn.
+        Verbatim(TokenStream),
+
+        // For testing exhaustiveness in downstream code, use the following idiom:
+        //
+        //     match item {
+        //         #![cfg_attr(test, deny(non_exhaustive_omitted_patterns))]
+        //
+        //         TraitItem::Const(item) => {...}
+        //         TraitItem::Fn(item) => {...}
+        //         ...
+        //         TraitItem::Verbatim(item) => {...}
+        //
+        //         _ => { /* 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! {
+    /// An associated constant within the definition of a trait.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct TraitItemConst {
+        pub attrs: Vec<Attribute>,
+        pub const_token: Token![const],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub colon_token: Token![:],
+        pub ty: Type,
+        pub default: Option<(Token![=], Expr)>,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// An associated function within the definition of a trait.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct TraitItemFn {
+        pub attrs: Vec<Attribute>,
+        pub sig: Signature,
+        pub default: Option<Block>,
+        pub semi_token: Option<Token![;]>,
+    }
+}
+
+ast_struct! {
+    /// An associated type within the definition of a trait.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct TraitItemType {
+        pub attrs: Vec<Attribute>,
+        pub type_token: Token![type],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub colon_token: Option<Token![:]>,
+        pub bounds: Punctuated<TypeParamBound, Token![+]>,
+        pub default: Option<(Token![=], Type)>,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A macro invocation within the definition of a trait.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct TraitItemMacro {
+        pub attrs: Vec<Attribute>,
+        pub mac: Macro,
+        pub semi_token: Option<Token![;]>,
+    }
+}
+
+ast_enum_of_structs! {
+    /// An item within an impl block.
+    ///
+    /// # Syntax tree enum
+    ///
+    /// This type is a [syntax tree enum].
+    ///
+    /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    #[non_exhaustive]
+    pub enum ImplItem {
+        /// An associated constant within an impl block.
+        Const(ImplItemConst),
+
+        /// An associated function within an impl block.
+        Fn(ImplItemFn),
+
+        /// An associated type within an impl block.
+        Type(ImplItemType),
+
+        /// A macro invocation within an impl block.
+        Macro(ImplItemMacro),
+
+        /// Tokens within an impl block not interpreted by Syn.
+        Verbatim(TokenStream),
+
+        // For testing exhaustiveness in downstream code, use the following idiom:
+        //
+        //     match item {
+        //         #![cfg_attr(test, deny(non_exhaustive_omitted_patterns))]
+        //
+        //         ImplItem::Const(item) => {...}
+        //         ImplItem::Fn(item) => {...}
+        //         ...
+        //         ImplItem::Verbatim(item) => {...}
+        //
+        //         _ => { /* 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! {
+    /// An associated constant within an impl block.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ImplItemConst {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub defaultness: Option<Token![default]>,
+        pub const_token: Token![const],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub colon_token: Token![:],
+        pub ty: Type,
+        pub eq_token: Token![=],
+        pub expr: Expr,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// An associated function within an impl block.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ImplItemFn {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub defaultness: Option<Token![default]>,
+        pub sig: Signature,
+        pub block: Block,
+    }
+}
+
+ast_struct! {
+    /// An associated type within an impl block.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ImplItemType {
+        pub attrs: Vec<Attribute>,
+        pub vis: Visibility,
+        pub defaultness: Option<Token![default]>,
+        pub type_token: Token![type],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub eq_token: Token![=],
+        pub ty: Type,
+        pub semi_token: Token![;],
+    }
+}
+
+ast_struct! {
+    /// A macro invocation within an impl block.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct ImplItemMacro {
+        pub attrs: Vec<Attribute>,
+        pub mac: Macro,
+        pub semi_token: Option<Token![;]>,
+    }
+}
+
+ast_struct! {
+    /// A function signature in a trait or implementation: `unsafe fn
+    /// initialize(&self)`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct Signature {
+        pub constness: Option<Token![const]>,
+        pub asyncness: Option<Token![async]>,
+        pub unsafety: Option<Token![unsafe]>,
+        pub abi: Option<Abi>,
+        pub fn_token: Token![fn],
+        pub ident: Ident,
+        pub generics: Generics,
+        pub paren_token: token::Paren,
+        pub inputs: Punctuated<FnArg, Token![,]>,
+        pub variadic: Option<Variadic>,
+        pub output: ReturnType,
+    }
+}
+
+impl Signature {
+    /// A method's `self` receiver, such as `&self` or `self: Box<Self>`.
+    pub fn receiver(&self) -> Option<&Receiver> {
+        let arg = self.inputs.first()?;
+        match arg {
+            FnArg::Receiver(receiver) => Some(receiver),
+            FnArg::Typed(_) => None,
+        }
+    }
+}
+
+ast_enum_of_structs! {
+    /// An argument in a function signature: the `n: usize` in `fn f(n: usize)`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub enum FnArg {
+        /// The `self` argument of an associated method.
+        Receiver(Receiver),
+
+        /// A function argument accepted by pattern and type.
+        Typed(PatType),
+    }
+}
+
+ast_struct! {
+    /// The `self` argument of an associated method.
+    ///
+    /// If `colon_token` is present, the receiver is written with an explicit
+    /// type such as `self: Box<Self>`. If `colon_token` is absent, the receiver
+    /// is written in shorthand such as `self` or `&self` or `&mut self`. In the
+    /// shorthand case, the type in `ty` is reconstructed as one of `Self`,
+    /// `&Self`, or `&mut Self`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct Receiver {
+        pub attrs: Vec<Attribute>,
+        pub reference: Option<(Token![&], Option<Lifetime>)>,
+        pub mutability: Option<Token![mut]>,
+        pub self_token: Token![self],
+        pub colon_token: Option<Token![:]>,
+        pub ty: Box<Type>,
+    }
+}
+
+impl Receiver {
+    pub fn lifetime(&self) -> Option<&Lifetime> {
+        self.reference.as_ref()?.1.as_ref()
+    }
+}
+
+ast_struct! {
+    /// The variadic argument of a foreign function.
+    ///
+    /// ```rust
+    /// # struct c_char;
+    /// # struct c_int;
+    /// #
+    /// extern "C" {
+    ///     fn printf(format: *const c_char, ...) -> c_int;
+    ///     //                               ^^^
+    /// }
+    /// ```
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    pub struct Variadic {
+        pub attrs: Vec<Attribute>,
+        pub pat: Option<(Box<Pat>, Token![:])>,
+        pub dots: Token![...],
+        pub comma: Option<Token![,]>,
+    }
+}
+
+ast_enum! {
+    /// The mutability of an `Item::Static` or `ForeignItem::Static`.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    #[non_exhaustive]
+    pub enum StaticMutability {
+        Mut(Token![mut]),
+        None,
+    }
+}
+
+ast_enum! {
+    /// Unused, but reserved for RFC 3323 restrictions.
+    #[cfg_attr(docsrs, doc(cfg(feature = "full")))]
+    #[non_exhaustive]
+    pub enum ImplRestriction {}
+
+
+    // TODO: https://rust-lang.github.io/rfcs/3323-restrictions.html
+    //
+    // pub struct ImplRestriction {
+    //     pub impl_token: Token![impl],
+    //     pub paren_token: token::Paren,
+    //     pub in_token: Option<Token![in]>,
+    //     pub path: Box<Path>,
+    // }
+}
+
+#[cfg(feature = "parsing")]
+pub(crate) mod parsing {
+    use crate::attr::{self, Attribute};
+    use crate::derive;
+    use crate::error::{Error, Result};
+    use crate::expr::Expr;
+    use crate::ext::IdentExt as _;
+    use crate::generics::{self, Generics, TypeParamBound};
+    use crate::ident::Ident;
+    use crate::item::{
+        FnArg, ForeignItem, ForeignItemFn, ForeignItemMacro, ForeignItemStatic, ForeignItemType,
+        ImplItem, ImplItemConst, ImplItemFn, ImplItemMacro, ImplItemType, Item, ItemConst,
+        ItemEnum, ItemExternCrate, ItemFn, ItemForeignMod, ItemImpl, ItemMacro, ItemMod,
+        ItemStatic, ItemStruct, ItemTrait, ItemTraitAlias, ItemType, ItemUnion, ItemUse, Receiver,
+        Signature, StaticMutability, TraitItem, TraitItemConst, TraitItemFn, TraitItemMacro,
+        TraitItemType, UseGlob, UseGroup, UseName, UsePath, UseRename, UseTree, Variadic,
+    };
+    use crate::lifetime::Lifetime;
+    use crate::lit::LitStr;
+    use crate::mac::{self, Macro};
+    use crate::parse::discouraged::Speculative as _;
+    use crate::parse::{Parse, ParseBuffer, ParseStream};
+    use crate::pat::{Pat, PatType, PatWild};
+    use crate::path::Path;
+    use crate::punctuated::Punctuated;
+    use crate::restriction::Visibility;
+    use crate::stmt::Block;
+    use crate::token;
+    use crate::ty::{Abi, ReturnType, Type, TypePath, TypeReference};
+    use crate::verbatim;
+    use proc_macro2::TokenStream;
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for Item {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let begin = input.fork();
+            let attrs = input.call(Attribute::parse_outer)?;
+            parse_rest_of_item(begin, attrs, input)
+        }
+    }
+
+    pub(crate) fn parse_rest_of_item(
+        begin: ParseBuffer,
+        mut attrs: Vec<Attribute>,
+        input: ParseStream,
+    ) -> Result<Item> {
+        let ahead = input.fork();
+        let vis: Visibility = ahead.parse()?;
+
+        let lookahead = ahead.lookahead1();
+        let allow_safe = false;
+        let mut item = if lookahead.peek(Token![fn]) || peek_signature(&ahead, allow_safe) {
+            let vis: Visibility = input.parse()?;
+            let sig: Signature = input.parse()?;
+            if input.peek(Token![;]) {
+                input.parse::<Token![;]>()?;
+                Ok(Item::Verbatim(verbatim::between(&begin, input)))
+            } else {
+                parse_rest_of_fn(input, Vec::new(), vis, sig).map(Item::Fn)
+            }
+        } else if lookahead.peek(Token![extern]) {
+            ahead.parse::<Token![extern]>()?;
+            let lookahead = ahead.lookahead1();
+            if lookahead.peek(Token![crate]) {
+                input.parse().map(Item::ExternCrate)
+            } else if lookahead.peek(token::Brace) {
+                input.parse().map(Item::ForeignMod)
+            } else if lookahead.peek(LitStr) {
+                ahead.parse::<LitStr>()?;
+                let lookahead = ahead.lookahead1();
+                if lookahead.peek(token::Brace) {
+                    input.parse().map(Item::ForeignMod)
+                } else {
+                    Err(lookahead.error())
+                }
+            } else {
+                Err(lookahead.error())
+            }
+        } else if lookahead.peek(Token![use]) {
+            let allow_crate_root_in_path = true;
+            match parse_item_use(input, allow_crate_root_in_path)? {
+                Some(item_use) => Ok(Item::Use(item_use)),
+                None => Ok(Item::Verbatim(verbatim::between(&begin, input))),
+            }
+        } else if lookahead.peek(Token![static]) {
+            let vis = input.parse()?;
+            let static_token = input.parse()?;
+            let mutability = input.parse()?;
+            let ident = input.parse()?;
+            if input.peek(Token![=]) {
+                input.parse::<Token![=]>()?;
+                input.parse::<Expr>()?;
+                input.parse::<Token![;]>()?;
+                Ok(Item::Verbatim(verbatim::between(&begin, input)))
+            } else {
+                let colon_token = input.parse()?;
+                let ty = input.parse()?;
+                if input.peek(Token![;]) {
+                    input.parse::<Token![;]>()?;
+                    Ok(Item::Verbatim(verbatim::between(&begin, input)))
+                } else {
+                    Ok(Item::Static(ItemStatic {
+                        attrs: Vec::new(),
+                        vis,
+                        static_token,
+                        mutability,
+                        ident,
+                        colon_token,
+                        ty,
+                        eq_token: input.parse()?,
+                        expr: input.parse()?,
+                        semi_token: input.parse()?,
+                    }))
+                }
+            }
+        } else if lookahead.peek(Token![const]) {
+            let vis = input.parse()?;
+            let const_token: Token![const] = input.parse()?;
+            let lookahead = input.lookahead1();
+            let ident = if lookahead.peek(Ident) || lookahead.peek(Token![_]) {
+                input.call(Ident::parse_any)?
+            } else {
+                return Err(lookahead.error());
+            };
+            let mut generics: Generics = input.parse()?;
+            let colon_token = input.parse()?;
+            let ty = input.parse()?;
+            let value = if let Some(eq_token) = input.parse::<Option<Token![=]>>()? {
+                let expr: Expr = input.parse()?;
+                Some((eq_token, expr))
+            } else {
+                None
+            };
+            generics.where_clause = input.parse()?;
+            let semi_token: Token![;] = input.parse()?;
+            match value {
+                Some((eq_token, expr))
+                    if generics.lt_token.is_none() && generics.where_clause.is_none() =>
+                {
+                    Ok(Item::Const(ItemConst {
+                        attrs: Vec::new(),
+                        vis,
+                        const_token,
+                        ident,
+                        generics,
+                        colon_token,
+                        ty,
+                        eq_token,
+                        expr: Box::new(expr),
+                        semi_token,
+                    }))
+                }
+                _ => Ok(Item::Verbatim(verbatim::between(&begin, input))),
+            }
+        } else if lookahead.peek(Token![unsafe]) {
+            ahead.parse::<Token![unsafe]>()?;
+            let lookahead = ahead.lookahead1();
+            if lookahead.peek(Token![trait])
+                || lookahead.peek(Token![auto]) && ahead.peek2(Token![trait])
+            {
+                input.parse().map(Item::Trait)
+            } else if lookahead.peek(Token![impl]) {
+                let allow_verbatim_impl = true;
+                if let Some(item) = parse_impl(input, allow_verbatim_impl)? {
+                    Ok(Item::Impl(item))
+                } else {
+                    Ok(Item::Verbatim(verbatim::between(&begin, input)))
+                }
+            } else if lookahead.peek(Token![extern]) {
+                input.parse().map(Item::ForeignMod)
+            } else if lookahead.peek(Token![mod]) {
+                input.parse().map(Item::Mod)
+            } else {
+                Err(lookahead.error())
+            }
+        } else if lookahead.peek(Token![mod]) {
+            input.parse().map(Item::Mod)
+        } else if lookahead.peek(Token![type]) {
+            parse_item_type(begin, input)
+        } else if lookahead.peek(Token![struct]) {
+            input.parse().map(Item::Struct)
+        } else if lookahead.peek(Token![enum]) {
+            input.parse().map(Item::Enum)
+        } else if lookahead.peek(Token![union]) && ahead.peek2(Ident) {
+            input.parse().map(Item::Union)
+        } else if lookahead.peek(Token![trait]) {
+            input.call(parse_trait_or_trait_alias)
+        } else if lookahead.peek(Token![auto]) && ahead.peek2(Token![trait]) {
+            input.parse().map(Item::Trait)
+        } else if lookahead.peek(Token![impl])
+            || lookahead.peek(Token![default]) && !ahead.peek2(Token![!])
+        {
+            let allow_verbatim_impl = true;
+            if let Some(item) = parse_impl(input, allow_verbatim_impl)? {
+                Ok(Item::Impl(item))
+            } else {
+                Ok(Item::Verbatim(verbatim::between(&begin, input)))
+            }
+        } else if lookahead.peek(Token![macro]) {
+            input.advance_to(&ahead);
+            parse_macro2(begin, vis, input)
+        } else if vis.is_inherited()
+            && (lookahead.peek(Ident)
+                || lookahead.peek(Token![self])
+                || lookahead.peek(Token![super])
+                || lookahead.peek(Token![crate])
+                || lookahead.peek(Token![::]))
+        {
+            input.parse().map(Item::Macro)
+        } else {
+            Err(lookahead.error())
+        }?;
+
+        attrs.extend(item.replace_attrs(Vec::new()));
+        item.replace_attrs(attrs);
+        Ok(item)
+    }
+
+    struct FlexibleItemType {
+        vis: Visibility,
+        defaultness: Option<Token![default]>,
+        type_token: Token![type],
+        ident: Ident,
+        generics: Generics,
+        colon_token: Option<Token![:]>,
+        bounds: Punctuated<TypeParamBound, Token![+]>,
+        ty: Option<(Token![=], Type)>,
+        semi_token: Token![;],
+    }
+
+    enum TypeDefaultness {
+        Optional,
+        Disallowed,
+    }
+
+    enum WhereClauseLocation {
+        // type Ty<T> where T: 'static = T;
+        BeforeEq,
+        // type Ty<T> = T where T: 'static;
+        AfterEq,
+        // TODO: goes away once the migration period on rust-lang/rust#89122 is over
+        Both,
+    }
+
+    impl FlexibleItemType {
+        fn parse(
+            input: ParseStream,
+            allow_defaultness: TypeDefaultness,
+            where_clause_location: WhereClauseLocation,
+        ) -> Result<Self> {
+            let vis: Visibility = input.parse()?;
+            let defaultness: Option<Token![default]> = match allow_defaultness {
+                TypeDefaultness::Optional => input.parse()?,
+                TypeDefaultness::Disallowed => None,
+            };
+            let type_token: Token![type] = input.parse()?;
+            let ident: Ident = input.parse()?;
+            let mut generics: Generics = input.parse()?;
+            let (colon_token, bounds) = Self::parse_optional_bounds(input)?;
+
+            match where_clause_location {
+                WhereClauseLocation::BeforeEq | WhereClauseLocation::Both => {
+                    generics.where_clause = input.parse()?;
+                }
+                WhereClauseLocation::AfterEq => {}
+            }
+
+            let ty = Self::parse_optional_definition(input)?;
+
+            match where_clause_location {
+                WhereClauseLocation::AfterEq | WhereClauseLocation::Both
+                    if generics.where_clause.is_none() =>
+                {
+                    generics.where_clause = input.parse()?;
+                }
+                _ => {}
+            }
+
+            let semi_token: Token![;] = input.parse()?;
+
+            Ok(FlexibleItemType {
+                vis,
+                defaultness,
+                type_token,
+                ident,
+                generics,
+                colon_token,
+                bounds,
+                ty,
+                semi_token,
+            })
+        }
+
+        fn parse_optional_bounds(
+            input: ParseStream,
+        ) -> Result<(Option<Token![:]>, Punctuated<TypeParamBound, Token![+]>)> {
+            let colon_token: Option<Token![:]> = input.parse()?;
+
+            let mut bounds = Punctuated::new();
+            if colon_token.is_some() {
+                loop {
+                    if input.peek(Token![where]) || input.peek(Token![=]) || input.peek(Token![;]) {
+                        break;
+                    }
+                    bounds.push_value({
+                        let allow_precise_capture = false;
+                        let allow_const = true;
+                        TypeParamBound::parse_single(input, allow_precise_capture, allow_const)?
+                    });
+                    if input.peek(Token![where]) || input.peek(Token![=]) || input.peek(Token![;]) {
+                        break;
+                    }
+                    bounds.push_punct(input.parse::<Token![+]>()?);
+                }
+            }
+
+            Ok((colon_token, bounds))
+        }
+
+        fn parse_optional_definition(input: ParseStream) -> Result<Option<(Token![=], Type)>> {
+            let eq_token: Option<Token![=]> = input.parse()?;
+            if let Some(eq_token) = eq_token {
+                let definition: Type = input.parse()?;
+                Ok(Some((eq_token, definition)))
+            } else {
+                Ok(None)
+            }
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemMacro {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let path = input.call(Path::parse_mod_style)?;
+            let bang_token: Token![!] = input.parse()?;
+            let ident: Option<Ident> = if input.peek(Token![try]) {
+                input.call(Ident::parse_any).map(Some)
+            } else {
+                input.parse()
+            }?;
+            let (delimiter, tokens) = input.call(mac::parse_delimiter)?;
+            let semi_token: Option<Token![;]> = if !delimiter.is_brace() {
+                Some(input.parse()?)
+            } else {
+                None
+            };
+            Ok(ItemMacro {
+                attrs,
+                ident,
+                mac: Macro {
+                    path,
+                    bang_token,
+                    delimiter,
+                    tokens,
+                },
+                semi_token,
+            })
+        }
+    }
+
+    fn parse_macro2(begin: ParseBuffer, _vis: Visibility, input: ParseStream) -> Result<Item> {
+        input.parse::<Token![macro]>()?;
+        input.parse::<Ident>()?;
+
+        let mut lookahead = input.lookahead1();
+        if lookahead.peek(token::Paren) {
+            let paren_content;
+            parenthesized!(paren_content in input);
+            paren_content.parse::<TokenStream>()?;
+            lookahead = input.lookahead1();
+        }
+
+        if lookahead.peek(token::Brace) {
+            let brace_content;
+            braced!(brace_content in input);
+            brace_content.parse::<TokenStream>()?;
+        } else {
+            return Err(lookahead.error());
+        }
+
+        Ok(Item::Verbatim(verbatim::between(&begin, input)))
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemExternCrate {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(ItemExternCrate {
+                attrs: input.call(Attribute::parse_outer)?,
+                vis: input.parse()?,
+                extern_token: input.parse()?,
+                crate_token: input.parse()?,
+                ident: {
+                    if input.peek(Token![self]) {
+                        input.call(Ident::parse_any)?
+                    } else {
+                        input.parse()?
+                    }
+                },
+                rename: {
+                    if input.peek(Token![as]) {
+                        let as_token: Token![as] = input.parse()?;
+                        let rename: Ident = if input.peek(Token![_]) {
+                            Ident::from(input.parse::<Token![_]>()?)
+                        } else {
+                            input.parse()?
+                        };
+                        Some((as_token, rename))
+                    } else {
+                        None
+                    }
+                },
+                semi_token: input.parse()?,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemUse {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let allow_crate_root_in_path = false;
+            parse_item_use(input, allow_crate_root_in_path).map(Option::unwrap)
+        }
+    }
+
+    fn parse_item_use(
+        input: ParseStream,
+        allow_crate_root_in_path: bool,
+    ) -> Result<Option<ItemUse>> {
+        let attrs = input.call(Attribute::parse_outer)?;
+        let vis: Visibility = input.parse()?;
+        let use_token: Token![use] = input.parse()?;
+        let leading_colon: Option<Token![::]> = input.parse()?;
+        let tree = parse_use_tree(input, allow_crate_root_in_path && leading_colon.is_none())?;
+        let semi_token: Token![;] = input.parse()?;
+
+        let tree = match tree {
+            Some(tree) => tree,
+            None => return Ok(None),
+        };
+
+        Ok(Some(ItemUse {
+            attrs,
+            vis,
+            use_token,
+            leading_colon,
+            tree,
+            semi_token,
+        }))
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for UseTree {
+        fn parse(input: ParseStream) -> Result<UseTree> {
+            let allow_crate_root_in_path = false;
+            parse_use_tree(input, allow_crate_root_in_path).map(Option::unwrap)
+        }
+    }
+
+    fn parse_use_tree(
+        input: ParseStream,
+        allow_crate_root_in_path: bool,
+    ) -> Result<Option<UseTree>> {
+        let lookahead = input.lookahead1();
+        if lookahead.peek(Ident)
+            || lookahead.peek(Token![self])
+            || lookahead.peek(Token![super])
+            || lookahead.peek(Token![crate])
+            || lookahead.peek(Token![try])
+        {
+            let ident = input.call(Ident::parse_any)?;
+            if input.peek(Token![::]) {
+                Ok(Some(UseTree::Path(UsePath {
+                    ident,
+                    colon2_token: input.parse()?,
+                    tree: Box::new(input.parse()?),
+                })))
+            } else if input.peek(Token![as]) {
+                Ok(Some(UseTree::Rename(UseRename {
+                    ident,
+                    as_token: input.parse()?,
+                    rename: {
+                        if input.peek(Ident) {
+                            input.parse()?
+                        } else if input.peek(Token![_]) {
+                            Ident::from(input.parse::<Token![_]>()?)
+                        } else {
+                            return Err(input.error("expected identifier or underscore"));
+                        }
+                    },
+                })))
+            } else {
+                Ok(Some(UseTree::Name(UseName { ident })))
+            }
+        } else if lookahead.peek(Token![*]) {
+            Ok(Some(UseTree::Glob(UseGlob {
+                star_token: input.parse()?,
+            })))
+        } else if lookahead.peek(token::Brace) {
+            let content;
+            let brace_token = braced!(content in input);
+            let mut items = Punctuated::new();
+            let mut has_any_crate_root_in_path = false;
+            loop {
+                if content.is_empty() {
+                    break;
+                }
+                let this_tree_starts_with_crate_root =
+                    allow_crate_root_in_path && content.parse::<Option<Token![::]>>()?.is_some();
+                has_any_crate_root_in_path |= this_tree_starts_with_crate_root;
+                match parse_use_tree(
+                    &content,
+                    allow_crate_root_in_path && !this_tree_starts_with_crate_root,
+                )? {
+                    Some(tree) if !has_any_crate_root_in_path => items.push_value(tree),
+                    _ => has_any_crate_root_in_path = true,
+                }
+                if content.is_empty() {
+                    break;
+                }
+                let comma: Token![,] = content.parse()?;
+                if !has_any_crate_root_in_path {
+                    items.push_punct(comma);
+                }
+            }
+            if has_any_crate_root_in_path {
+                Ok(None)
+            } else {
+                Ok(Some(UseTree::Group(UseGroup { brace_token, items })))
+            }
+        } else {
+            Err(lookahead.error())
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemStatic {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(ItemStatic {
+                attrs: input.call(Attribute::parse_outer)?,
+                vis: input.parse()?,
+                static_token: input.parse()?,
+                mutability: input.parse()?,
+                ident: input.parse()?,
+                colon_token: input.parse()?,
+                ty: input.parse()?,
+                eq_token: input.parse()?,
+                expr: input.parse()?,
+                semi_token: input.parse()?,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemConst {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let vis: Visibility = input.parse()?;
+            let const_token: Token![const] = input.parse()?;
+
+            let lookahead = input.lookahead1();
+            let ident = if lookahead.peek(Ident) || lookahead.peek(Token![_]) {
+                input.call(Ident::parse_any)?
+            } else {
+                return Err(lookahead.error());
+            };
+
+            let colon_token: Token![:] = input.parse()?;
+            let ty: Type = input.parse()?;
+            let eq_token: Token![=] = input.parse()?;
+            let expr: Expr = input.parse()?;
+            let semi_token: Token![;] = input.parse()?;
+
+            Ok(ItemConst {
+                attrs,
+                vis,
+                const_token,
+                ident,
+                generics: Generics::default(),
+                colon_token,
+                ty: Box::new(ty),
+                eq_token,
+                expr: Box::new(expr),
+                semi_token,
+            })
+        }
+    }
+
+    fn peek_signature(input: ParseStream, allow_safe: bool) -> bool {
+        let fork = input.fork();
+        fork.parse::<Option<Token![const]>>().is_ok()
+            && fork.parse::<Option<Token![async]>>().is_ok()
+            && ((allow_safe
+                && token::parsing::peek_keyword(fork.cursor(), "safe")
+                && token::parsing::keyword(&fork, "safe").is_ok())
+                || fork.parse::<Option<Token![unsafe]>>().is_ok())
+            && fork.parse::<Option<Abi>>().is_ok()
+            && fork.peek(Token![fn])
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for Signature {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let allow_safe = false;
+            parse_signature(input, allow_safe).map(Option::unwrap)
+        }
+    }
+
+    fn parse_signature(input: ParseStream, allow_safe: bool) -> Result<Option<Signature>> {
+        let constness: Option<Token![const]> = input.parse()?;
+        let asyncness: Option<Token![async]> = input.parse()?;
+        let unsafety: Option<Token![unsafe]> = input.parse()?;
+        let safe = allow_safe
+            && unsafety.is_none()
+            && token::parsing::peek_keyword(input.cursor(), "safe");
+        if safe {
+            token::parsing::keyword(input, "safe")?;
+        }
+        let abi: Option<Abi> = input.parse()?;
+        let fn_token: Token![fn] = input.parse()?;
+        let ident: Ident = input.parse()?;
+        let mut generics: Generics = input.parse()?;
+
+        let content;
+        let paren_token = parenthesized!(content in input);
+        let (inputs, variadic) = parse_fn_args(&content)?;
+
+        let output: ReturnType = input.parse()?;
+        generics.where_clause = input.parse()?;
+
+        Ok(if safe {
+            None
+        } else {
+            Some(Signature {
+                constness,
+                asyncness,
+                unsafety,
+                abi,
+                fn_token,
+                ident,
+                generics,
+                paren_token,
+                inputs,
+                variadic,
+                output,
+            })
+        })
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemFn {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let outer_attrs = input.call(Attribute::parse_outer)?;
+            let vis: Visibility = input.parse()?;
+            let sig: Signature = input.parse()?;
+            parse_rest_of_fn(input, outer_attrs, vis, sig)
+        }
+    }
+
+    fn parse_rest_of_fn(
+        input: ParseStream,
+        mut attrs: Vec<Attribute>,
+        vis: Visibility,
+        sig: Signature,
+    ) -> Result<ItemFn> {
+        let content;
+        let brace_token = braced!(content in input);
+        attr::parsing::parse_inner(&content, &mut attrs)?;
+        let stmts = content.call(Block::parse_within)?;
+
+        Ok(ItemFn {
+            attrs,
+            vis,
+            sig,
+            block: Box::new(Block { brace_token, stmts }),
+        })
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for FnArg {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let allow_variadic = false;
+            let attrs = input.call(Attribute::parse_outer)?;
+            match parse_fn_arg_or_variadic(input, attrs, allow_variadic)? {
+                FnArgOrVariadic::FnArg(arg) => Ok(arg),
+                FnArgOrVariadic::Variadic(_) => unreachable!(),
+            }
+        }
+    }
+
+    enum FnArgOrVariadic {
+        FnArg(FnArg),
+        Variadic(Variadic),
+    }
+
+    fn parse_fn_arg_or_variadic(
+        input: ParseStream,
+        attrs: Vec<Attribute>,
+        allow_variadic: bool,
+    ) -> Result<FnArgOrVariadic> {
+        let ahead = input.fork();
+        if let Ok(mut receiver) = ahead.parse::<Receiver>() {
+            input.advance_to(&ahead);
+            receiver.attrs = attrs;
+            return Ok(FnArgOrVariadic::FnArg(FnArg::Receiver(receiver)));
+        }
+
+        // Hack to parse pre-2018 syntax in
+        // test/ui/rfc-2565-param-attrs/param-attrs-pretty.rs
+        // because the rest of the test case is valuable.
+        if input.peek(Ident) && input.peek2(Token![<]) {
+            let span = input.span();
+            return Ok(FnArgOrVariadic::FnArg(FnArg::Typed(PatType {
+                attrs,
+                pat: Box::new(Pat::Wild(PatWild {
+                    attrs: Vec::new(),
+                    underscore_token: Token![_](span),
+                })),
+                colon_token: Token![:](span),
+                ty: input.parse()?,
+            })));
+        }
+
+        let pat = Box::new(Pat::parse_single(input)?);
+        let colon_token: Token![:] = input.parse()?;
+
+        if allow_variadic {
+            if let Some(dots) = input.parse::<Option<Token![...]>>()? {
+                return Ok(FnArgOrVariadic::Variadic(Variadic {
+                    attrs,
+                    pat: Some((pat, colon_token)),
+                    dots,
+                    comma: None,
+                }));
+            }
+        }
+
+        Ok(FnArgOrVariadic::FnArg(FnArg::Typed(PatType {
+            attrs,
+            pat,
+            colon_token,
+            ty: input.parse()?,
+        })))
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for Receiver {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let reference = if input.peek(Token![&]) {
+                let ampersand: Token![&] = input.parse()?;
+                let lifetime: Option<Lifetime> = input.parse()?;
+                Some((ampersand, lifetime))
+            } else {
+                None
+            };
+            let mutability: Option<Token![mut]> = input.parse()?;
+            let self_token: Token![self] = input.parse()?;
+            let colon_token: Option<Token![:]> = if reference.is_some() {
+                None
+            } else {
+                input.parse()?
+            };
+            let ty: Type = if colon_token.is_some() {
+                input.parse()?
+            } else {
+                let mut ty = Type::Path(TypePath {
+                    qself: None,
+                    path: Path::from(Ident::new("Self", self_token.span)),
+                });
+                if let Some((ampersand, lifetime)) = reference.as_ref() {
+                    ty = Type::Reference(TypeReference {
+                        and_token: Token![&](ampersand.span),
+                        lifetime: lifetime.clone(),
+                        mutability: mutability.as_ref().map(|m| Token![mut](m.span)),
+                        elem: Box::new(ty),
+                    });
+                }
+                ty
+            };
+            Ok(Receiver {
+                attrs: Vec::new(),
+                reference,
+                mutability,
+                self_token,
+                colon_token,
+                ty: Box::new(ty),
+            })
+        }
+    }
+
+    fn parse_fn_args(
+        input: ParseStream,
+    ) -> Result<(Punctuated<FnArg, Token![,]>, Option<Variadic>)> {
+        let mut args = Punctuated::new();
+        let mut variadic = None;
+        let mut has_receiver = false;
+
+        while !input.is_empty() {
+            let attrs = input.call(Attribute::parse_outer)?;
+
+            if let Some(dots) = input.parse::<Option<Token![...]>>()? {
+                variadic = Some(Variadic {
+                    attrs,
+                    pat: None,
+                    dots,
+                    comma: if input.is_empty() {
+                        None
+                    } else {
+                        Some(input.parse()?)
+                    },
+                });
+                break;
+            }
+
+            let allow_variadic = true;
+            let arg = match parse_fn_arg_or_variadic(input, attrs, allow_variadic)? {
+                FnArgOrVariadic::FnArg(arg) => arg,
+                FnArgOrVariadic::Variadic(arg) => {
+                    variadic = Some(Variadic {
+                        comma: if input.is_empty() {
+                            None
+                        } else {
+                            Some(input.parse()?)
+                        },
+                        ..arg
+                    });
+                    break;
+                }
+            };
+
+            match &arg {
+                FnArg::Receiver(receiver) if has_receiver => {
+                    return Err(Error::new(
+                        receiver.self_token.span,
+                        "unexpected second method receiver",
+                    ));
+                }
+                FnArg::Receiver(receiver) if !args.is_empty() => {
+                    return Err(Error::new(
+                        receiver.self_token.span,
+                        "unexpected method receiver",
+                    ));
+                }
+                FnArg::Receiver(_) => has_receiver = true,
+                FnArg::Typed(_) => {}
+            }
+            args.push_value(arg);
+
+            if input.is_empty() {
+                break;
+            }
+
+            let comma: Token![,] = input.parse()?;
+            args.push_punct(comma);
+        }
+
+        Ok((args, variadic))
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemMod {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let mut attrs = input.call(Attribute::parse_outer)?;
+            let vis: Visibility = input.parse()?;
+            let unsafety: Option<Token![unsafe]> = input.parse()?;
+            let mod_token: Token![mod] = input.parse()?;
+            let ident: Ident = if input.peek(Token![try]) {
+                input.call(Ident::parse_any)
+            } else {
+                input.parse()
+            }?;
+
+            let lookahead = input.lookahead1();
+            if lookahead.peek(Token![;]) {
+                Ok(ItemMod {
+                    attrs,
+                    vis,
+                    unsafety,
+                    mod_token,
+                    ident,
+                    content: None,
+                    semi: Some(input.parse()?),
+                })
+            } else if lookahead.peek(token::Brace) {
+                let content;
+                let brace_token = braced!(content in input);
+                attr::parsing::parse_inner(&content, &mut attrs)?;
+
+                let mut items = Vec::new();
+                while !content.is_empty() {
+                    items.push(content.parse()?);
+                }
+
+                Ok(ItemMod {
+                    attrs,
+                    vis,
+                    unsafety,
+                    mod_token,
+                    ident,
+                    content: Some((brace_token, items)),
+                    semi: None,
+                })
+            } else {
+                Err(lookahead.error())
+            }
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemForeignMod {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let mut attrs = input.call(Attribute::parse_outer)?;
+            let unsafety: Option<Token![unsafe]> = input.parse()?;
+            let abi: Abi = input.parse()?;
+
+            let content;
+            let brace_token = braced!(content in input);
+            attr::parsing::parse_inner(&content, &mut attrs)?;
+            let mut items = Vec::new();
+            while !content.is_empty() {
+                items.push(content.parse()?);
+            }
+
+            Ok(ItemForeignMod {
+                attrs,
+                unsafety,
+                abi,
+                brace_token,
+                items,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ForeignItem {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let begin = input.fork();
+            let mut attrs = input.call(Attribute::parse_outer)?;
+            let ahead = input.fork();
+            let vis: Visibility = ahead.parse()?;
+
+            let lookahead = ahead.lookahead1();
+            let allow_safe = true;
+            let mut item = if lookahead.peek(Token![fn]) || peek_signature(&ahead, allow_safe) {
+                let vis: Visibility = input.parse()?;
+                let sig = parse_signature(input, allow_safe)?;
+                let has_safe = sig.is_none();
+                let has_body = input.peek(token::Brace);
+                let semi_token: Option<Token![;]> = if has_body {
+                    let content;
+                    braced!(content in input);
+                    content.call(Attribute::parse_inner)?;
+                    content.call(Block::parse_within)?;
+                    None
+                } else {
+                    Some(input.parse()?)
+                };
+                if has_safe || has_body {
+                    Ok(ForeignItem::Verbatim(verbatim::between(&begin, input)))
+                } else {
+                    Ok(ForeignItem::Fn(ForeignItemFn {
+                        attrs: Vec::new(),
+                        vis,
+                        sig: sig.unwrap(),
+                        semi_token: semi_token.unwrap(),
+                    }))
+                }
+            } else if lookahead.peek(Token![static])
+                || ((ahead.peek(Token![unsafe])
+                    || token::parsing::peek_keyword(ahead.cursor(), "safe"))
+                    && ahead.peek2(Token![static]))
+            {
+                let vis = input.parse()?;
+                let unsafety: Option<Token![unsafe]> = input.parse()?;
+                let safe =
+                    unsafety.is_none() && token::parsing::peek_keyword(input.cursor(), "safe");
+                if safe {
+                    token::parsing::keyword(input, "safe")?;
+                }
+                let static_token = input.parse()?;
+                let mutability = input.parse()?;
+                let ident = input.parse()?;
+                let colon_token = input.parse()?;
+                let ty = input.parse()?;
+                let has_value = input.peek(Token![=]);
+                if has_value {
+                    input.parse::<Token![=]>()?;
+                    input.parse::<Expr>()?;
+                }
+                let semi_token: Token![;] = input.parse()?;
+                if unsafety.is_some() || safe || has_value {
+                    Ok(ForeignItem::Verbatim(verbatim::between(&begin, input)))
+                } else {
+                    Ok(ForeignItem::Static(ForeignItemStatic {
+                        attrs: Vec::new(),
+                        vis,
+                        static_token,
+                        mutability,
+                        ident,
+                        colon_token,
+                        ty,
+                        semi_token,
+                    }))
+                }
+            } else if lookahead.peek(Token![type]) {
+                parse_foreign_item_type(begin, input)
+            } else if vis.is_inherited()
+                && (lookahead.peek(Ident)
+                    || lookahead.peek(Token![self])
+                    || lookahead.peek(Token![super])
+                    || lookahead.peek(Token![crate])
+                    || lookahead.peek(Token![::]))
+            {
+                input.parse().map(ForeignItem::Macro)
+            } else {
+                Err(lookahead.error())
+            }?;
+
+            let item_attrs = match &mut item {
+                ForeignItem::Fn(item) => &mut item.attrs,
+                ForeignItem::Static(item) => &mut item.attrs,
+                ForeignItem::Type(item) => &mut item.attrs,
+                ForeignItem::Macro(item) => &mut item.attrs,
+                ForeignItem::Verbatim(_) => return Ok(item),
+            };
+            attrs.append(item_attrs);
+            *item_attrs = attrs;
+
+            Ok(item)
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ForeignItemFn {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let vis: Visibility = input.parse()?;
+            let sig: Signature = input.parse()?;
+            let semi_token: Token![;] = input.parse()?;
+            Ok(ForeignItemFn {
+                attrs,
+                vis,
+                sig,
+                semi_token,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ForeignItemStatic {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(ForeignItemStatic {
+                attrs: input.call(Attribute::parse_outer)?,
+                vis: input.parse()?,
+                static_token: input.parse()?,
+                mutability: input.parse()?,
+                ident: input.parse()?,
+                colon_token: input.parse()?,
+                ty: input.parse()?,
+                semi_token: input.parse()?,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ForeignItemType {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(ForeignItemType {
+                attrs: input.call(Attribute::parse_outer)?,
+                vis: input.parse()?,
+                type_token: input.parse()?,
+                ident: input.parse()?,
+                generics: {
+                    let mut generics: Generics = input.parse()?;
+                    generics.where_clause = input.parse()?;
+                    generics
+                },
+                semi_token: input.parse()?,
+            })
+        }
+    }
+
+    fn parse_foreign_item_type(begin: ParseBuffer, input: ParseStream) -> Result<ForeignItem> {
+        let FlexibleItemType {
+            vis,
+            defaultness: _,
+            type_token,
+            ident,
+            generics,
+            colon_token,
+            bounds: _,
+            ty,
+            semi_token,
+        } = FlexibleItemType::parse(
+            input,
+            TypeDefaultness::Disallowed,
+            WhereClauseLocation::Both,
+        )?;
+
+        if colon_token.is_some() || ty.is_some() {
+            Ok(ForeignItem::Verbatim(verbatim::between(&begin, input)))
+        } else {
+            Ok(ForeignItem::Type(ForeignItemType {
+                attrs: Vec::new(),
+                vis,
+                type_token,
+                ident,
+                generics,
+                semi_token,
+            }))
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ForeignItemMacro {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let mac: Macro = input.parse()?;
+            let semi_token: Option<Token![;]> = if mac.delimiter.is_brace() {
+                None
+            } else {
+                Some(input.parse()?)
+            };
+            Ok(ForeignItemMacro {
+                attrs,
+                mac,
+                semi_token,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemType {
+        fn parse(input: ParseStream) -> Result<Self> {
+            Ok(ItemType {
+                attrs: input.call(Attribute::parse_outer)?,
+                vis: input.parse()?,
+                type_token: input.parse()?,
+                ident: input.parse()?,
+                generics: {
+                    let mut generics: Generics = input.parse()?;
+                    generics.where_clause = input.parse()?;
+                    generics
+                },
+                eq_token: input.parse()?,
+                ty: input.parse()?,
+                semi_token: input.parse()?,
+            })
+        }
+    }
+
+    fn parse_item_type(begin: ParseBuffer, input: ParseStream) -> Result<Item> {
+        let FlexibleItemType {
+            vis,
+            defaultness: _,
+            type_token,
+            ident,
+            generics,
+            colon_token,
+            bounds: _,
+            ty,
+            semi_token,
+        } = FlexibleItemType::parse(
+            input,
+            TypeDefaultness::Disallowed,
+            WhereClauseLocation::BeforeEq,
+        )?;
+
+        let (eq_token, ty) = match ty {
+            Some(ty) if colon_token.is_none() => ty,
+            _ => return Ok(Item::Verbatim(verbatim::between(&begin, input))),
+        };
+
+        Ok(Item::Type(ItemType {
+            attrs: Vec::new(),
+            vis,
+            type_token,
+            ident,
+            generics,
+            eq_token,
+            ty: Box::new(ty),
+            semi_token,
+        }))
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemStruct {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let vis = input.parse::<Visibility>()?;
+            let struct_token = input.parse::<Token![struct]>()?;
+            let ident = input.parse::<Ident>()?;
+            let generics = input.parse::<Generics>()?;
+            let (where_clause, fields, semi_token) = derive::parsing::data_struct(input)?;
+            Ok(ItemStruct {
+                attrs,
+                vis,
+                struct_token,
+                ident,
+                generics: Generics {
+                    where_clause,
+                    ..generics
+                },
+                fields,
+                semi_token,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemEnum {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let vis = input.parse::<Visibility>()?;
+            let enum_token = input.parse::<Token![enum]>()?;
+            let ident = input.parse::<Ident>()?;
+            let generics = input.parse::<Generics>()?;
+            let (where_clause, brace_token, variants) = derive::parsing::data_enum(input)?;
+            Ok(ItemEnum {
+                attrs,
+                vis,
+                enum_token,
+                ident,
+                generics: Generics {
+                    where_clause,
+                    ..generics
+                },
+                brace_token,
+                variants,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemUnion {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let vis = input.parse::<Visibility>()?;
+            let union_token = input.parse::<Token![union]>()?;
+            let ident = input.parse::<Ident>()?;
+            let generics = input.parse::<Generics>()?;
+            let (where_clause, fields) = derive::parsing::data_union(input)?;
+            Ok(ItemUnion {
+                attrs,
+                vis,
+                union_token,
+                ident,
+                generics: Generics {
+                    where_clause,
+                    ..generics
+                },
+                fields,
+            })
+        }
+    }
+
+    fn parse_trait_or_trait_alias(input: ParseStream) -> Result<Item> {
+        let (attrs, vis, trait_token, ident, generics) = parse_start_of_trait_alias(input)?;
+        let lookahead = input.lookahead1();
+        if lookahead.peek(token::Brace)
+            || lookahead.peek(Token![:])
+            || lookahead.peek(Token![where])
+        {
+            let unsafety = None;
+            let auto_token = None;
+            parse_rest_of_trait(
+                input,
+                attrs,
+                vis,
+                unsafety,
+                auto_token,
+                trait_token,
+                ident,
+                generics,
+            )
+            .map(Item::Trait)
+        } else if lookahead.peek(Token![=]) {
+            parse_rest_of_trait_alias(input, attrs, vis, trait_token, ident, generics)
+                .map(Item::TraitAlias)
+        } else {
+            Err(lookahead.error())
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemTrait {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let outer_attrs = input.call(Attribute::parse_outer)?;
+            let vis: Visibility = input.parse()?;
+            let unsafety: Option<Token![unsafe]> = input.parse()?;
+            let auto_token: Option<Token![auto]> = input.parse()?;
+            let trait_token: Token![trait] = input.parse()?;
+            let ident: Ident = input.parse()?;
+            let generics: Generics = input.parse()?;
+            parse_rest_of_trait(
+                input,
+                outer_attrs,
+                vis,
+                unsafety,
+                auto_token,
+                trait_token,
+                ident,
+                generics,
+            )
+        }
+    }
+
+    fn parse_rest_of_trait(
+        input: ParseStream,
+        mut attrs: Vec<Attribute>,
+        vis: Visibility,
+        unsafety: Option<Token![unsafe]>,
+        auto_token: Option<Token![auto]>,
+        trait_token: Token![trait],
+        ident: Ident,
+        mut generics: Generics,
+    ) -> Result<ItemTrait> {
+        let colon_token: Option<Token![:]> = input.parse()?;
+
+        let mut supertraits = Punctuated::new();
+        if colon_token.is_some() {
+            loop {
+                if input.peek(Token![where]) || input.peek(token::Brace) {
+                    break;
+                }
+                supertraits.push_value({
+                    let allow_precise_capture = false;
+                    let allow_const = true;
+                    TypeParamBound::parse_single(input, allow_precise_capture, allow_const)?
+                });
+                if input.peek(Token![where]) || input.peek(token::Brace) {
+                    break;
+                }
+                supertraits.push_punct(input.parse()?);
+            }
+        }
+
+        generics.where_clause = input.parse()?;
+
+        let content;
+        let brace_token = braced!(content in input);
+        attr::parsing::parse_inner(&content, &mut attrs)?;
+        let mut items = Vec::new();
+        while !content.is_empty() {
+            items.push(content.parse()?);
+        }
+
+        Ok(ItemTrait {
+            attrs,
+            vis,
+            unsafety,
+            auto_token,
+            restriction: None,
+            trait_token,
+            ident,
+            generics,
+            colon_token,
+            supertraits,
+            brace_token,
+            items,
+        })
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemTraitAlias {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let (attrs, vis, trait_token, ident, generics) = parse_start_of_trait_alias(input)?;
+            parse_rest_of_trait_alias(input, attrs, vis, trait_token, ident, generics)
+        }
+    }
+
+    fn parse_start_of_trait_alias(
+        input: ParseStream,
+    ) -> Result<(Vec<Attribute>, Visibility, Token![trait], Ident, Generics)> {
+        let attrs = input.call(Attribute::parse_outer)?;
+        let vis: Visibility = input.parse()?;
+        let trait_token: Token![trait] = input.parse()?;
+        let ident: Ident = input.parse()?;
+        let generics: Generics = input.parse()?;
+        Ok((attrs, vis, trait_token, ident, generics))
+    }
+
+    fn parse_rest_of_trait_alias(
+        input: ParseStream,
+        attrs: Vec<Attribute>,
+        vis: Visibility,
+        trait_token: Token![trait],
+        ident: Ident,
+        mut generics: Generics,
+    ) -> Result<ItemTraitAlias> {
+        let eq_token: Token![=] = input.parse()?;
+
+        let mut bounds = Punctuated::new();
+        loop {
+            if input.peek(Token![where]) || input.peek(Token![;]) {
+                break;
+            }
+            bounds.push_value({
+                let allow_precise_capture = false;
+                let allow_const = false;
+                TypeParamBound::parse_single(input, allow_precise_capture, allow_const)?
+            });
+            if input.peek(Token![where]) || input.peek(Token![;]) {
+                break;
+            }
+            bounds.push_punct(input.parse()?);
+        }
+
+        generics.where_clause = input.parse()?;
+        let semi_token: Token![;] = input.parse()?;
+
+        Ok(ItemTraitAlias {
+            attrs,
+            vis,
+            trait_token,
+            ident,
+            generics,
+            eq_token,
+            bounds,
+            semi_token,
+        })
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for TraitItem {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let begin = input.fork();
+            let mut attrs = input.call(Attribute::parse_outer)?;
+            let vis: Visibility = input.parse()?;
+            let defaultness: Option<Token![default]> = input.parse()?;
+            let ahead = input.fork();
+
+            let lookahead = ahead.lookahead1();
+            let allow_safe = false;
+            let mut item = if lookahead.peek(Token![fn]) || peek_signature(&ahead, allow_safe) {
+                input.parse().map(TraitItem::Fn)
+            } else if lookahead.peek(Token![const]) {
+                let const_token: Token![const] = ahead.parse()?;
+                let lookahead = ahead.lookahead1();
+                if lookahead.peek(Ident) || lookahead.peek(Token![_]) {
+                    input.advance_to(&ahead);
+                    let ident = input.call(Ident::parse_any)?;
+                    let mut generics: Generics = input.parse()?;
+                    let colon_token: Token![:] = input.parse()?;
+                    let ty: Type = input.parse()?;
+                    let default = if let Some(eq_token) = input.parse::<Option<Token![=]>>()? {
+                        let expr: Expr = input.parse()?;
+                        Some((eq_token, expr))
+                    } else {
+                        None
+                    };
+                    generics.where_clause = input.parse()?;
+                    let semi_token: Token![;] = input.parse()?;
+                    if generics.lt_token.is_none() && generics.where_clause.is_none() {
+                        Ok(TraitItem::Const(TraitItemConst {
+                            attrs: Vec::new(),
+                            const_token,
+                            ident,
+                            generics,
+                            colon_token,
+                            ty,
+                            default,
+                            semi_token,
+                        }))
+                    } else {
+                        return Ok(TraitItem::Verbatim(verbatim::between(&begin, input)));
+                    }
+                } else if lookahead.peek(Token![async])
+                    || lookahead.peek(Token![unsafe])
+                    || lookahead.peek(Token![extern])
+                    || lookahead.peek(Token![fn])
+                {
+                    input.parse().map(TraitItem::Fn)
+                } else {
+                    Err(lookahead.error())
+                }
+            } else if lookahead.peek(Token![type]) {
+                parse_trait_item_type(begin.fork(), input)
+            } else if vis.is_inherited()
+                && defaultness.is_none()
+                && (lookahead.peek(Ident)
+                    || lookahead.peek(Token![self])
+                    || lookahead.peek(Token![super])
+                    || lookahead.peek(Token![crate])
+                    || lookahead.peek(Token![::]))
+            {
+                input.parse().map(TraitItem::Macro)
+            } else {
+                Err(lookahead.error())
+            }?;
+
+            match (vis, defaultness) {
+                (Visibility::Inherited, None) => {}
+                _ => return Ok(TraitItem::Verbatim(verbatim::between(&begin, input))),
+            }
+
+            let item_attrs = match &mut item {
+                TraitItem::Const(item) => &mut item.attrs,
+                TraitItem::Fn(item) => &mut item.attrs,
+                TraitItem::Type(item) => &mut item.attrs,
+                TraitItem::Macro(item) => &mut item.attrs,
+                TraitItem::Verbatim(_) => unreachable!(),
+            };
+            attrs.append(item_attrs);
+            *item_attrs = attrs;
+            Ok(item)
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for TraitItemConst {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let const_token: Token![const] = input.parse()?;
+
+            let lookahead = input.lookahead1();
+            let ident = if lookahead.peek(Ident) || lookahead.peek(Token![_]) {
+                input.call(Ident::parse_any)?
+            } else {
+                return Err(lookahead.error());
+            };
+
+            let colon_token: Token![:] = input.parse()?;
+            let ty: Type = input.parse()?;
+            let default = if input.peek(Token![=]) {
+                let eq_token: Token![=] = input.parse()?;
+                let default: Expr = input.parse()?;
+                Some((eq_token, default))
+            } else {
+                None
+            };
+            let semi_token: Token![;] = input.parse()?;
+
+            Ok(TraitItemConst {
+                attrs,
+                const_token,
+                ident,
+                generics: Generics::default(),
+                colon_token,
+                ty,
+                default,
+                semi_token,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for TraitItemFn {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let mut attrs = input.call(Attribute::parse_outer)?;
+            let sig: Signature = input.parse()?;
+
+            let lookahead = input.lookahead1();
+            let (brace_token, stmts, semi_token) = if lookahead.peek(token::Brace) {
+                let content;
+                let brace_token = braced!(content in input);
+                attr::parsing::parse_inner(&content, &mut attrs)?;
+                let stmts = content.call(Block::parse_within)?;
+                (Some(brace_token), stmts, None)
+            } else if lookahead.peek(Token![;]) {
+                let semi_token: Token![;] = input.parse()?;
+                (None, Vec::new(), Some(semi_token))
+            } else {
+                return Err(lookahead.error());
+            };
+
+            Ok(TraitItemFn {
+                attrs,
+                sig,
+                default: brace_token.map(|brace_token| Block { brace_token, stmts }),
+                semi_token,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for TraitItemType {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let type_token: Token![type] = input.parse()?;
+            let ident: Ident = input.parse()?;
+            let mut generics: Generics = input.parse()?;
+            let (colon_token, bounds) = FlexibleItemType::parse_optional_bounds(input)?;
+            let default = FlexibleItemType::parse_optional_definition(input)?;
+            generics.where_clause = input.parse()?;
+            let semi_token: Token![;] = input.parse()?;
+            Ok(TraitItemType {
+                attrs,
+                type_token,
+                ident,
+                generics,
+                colon_token,
+                bounds,
+                default,
+                semi_token,
+            })
+        }
+    }
+
+    fn parse_trait_item_type(begin: ParseBuffer, input: ParseStream) -> Result<TraitItem> {
+        let FlexibleItemType {
+            vis,
+            defaultness: _,
+            type_token,
+            ident,
+            generics,
+            colon_token,
+            bounds,
+            ty,
+            semi_token,
+        } = FlexibleItemType::parse(
+            input,
+            TypeDefaultness::Disallowed,
+            WhereClauseLocation::AfterEq,
+        )?;
+
+        if vis.is_some() {
+            Ok(TraitItem::Verbatim(verbatim::between(&begin, input)))
+        } else {
+            Ok(TraitItem::Type(TraitItemType {
+                attrs: Vec::new(),
+                type_token,
+                ident,
+                generics,
+                colon_token,
+                bounds,
+                default: ty,
+                semi_token,
+            }))
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for TraitItemMacro {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let mac: Macro = input.parse()?;
+            let semi_token: Option<Token![;]> = if mac.delimiter.is_brace() {
+                None
+            } else {
+                Some(input.parse()?)
+            };
+            Ok(TraitItemMacro {
+                attrs,
+                mac,
+                semi_token,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ItemImpl {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let allow_verbatim_impl = false;
+            parse_impl(input, allow_verbatim_impl).map(Option::unwrap)
+        }
+    }
+
+    fn parse_impl(input: ParseStream, allow_verbatim_impl: bool) -> Result<Option<ItemImpl>> {
+        let mut attrs = input.call(Attribute::parse_outer)?;
+        let has_visibility = allow_verbatim_impl && input.parse::<Visibility>()?.is_some();
+        let defaultness: Option<Token![default]> = input.parse()?;
+        let unsafety: Option<Token![unsafe]> = input.parse()?;
+        let impl_token: Token![impl] = input.parse()?;
+
+        let has_generics = generics::parsing::choose_generics_over_qpath(input);
+        let mut generics: Generics = if has_generics {
+            input.parse()?
+        } else {
+            Generics::default()
+        };
+
+        let is_const_impl = allow_verbatim_impl
+            && (input.peek(Token![const]) || input.peek(Token![?]) && input.peek2(Token![const]));
+        if is_const_impl {
+            input.parse::<Option<Token![?]>>()?;
+            input.parse::<Token![const]>()?;
+        }
+
+        let polarity = if input.peek(Token![!]) && !input.peek2(token::Brace) {
+            Some(input.parse::<Token![!]>()?)
+        } else {
+            None
+        };
+
+        #[cfg(not(feature = "printing"))]
+        let first_ty_span = input.span();
+        let mut first_ty: Type = input.parse()?;
+        let self_ty: Type;
+        let trait_;
+
+        let is_impl_for = input.peek(Token![for]);
+        if is_impl_for {
+            let for_token: Token![for] = input.parse()?;
+            let mut first_ty_ref = &first_ty;
+            while let Type::Group(ty) = first_ty_ref {
+                first_ty_ref = &ty.elem;
+            }
+            if let Type::Path(TypePath { qself: None, .. }) = first_ty_ref {
+                while let Type::Group(ty) = first_ty {
+                    first_ty = *ty.elem;
+                }
+                if let Type::Path(TypePath { qself: None, path }) = first_ty {
+                    trait_ = Some((polarity, path, for_token));
+                } else {
+                    unreachable!();
+                }
+            } else if !allow_verbatim_impl {
+                #[cfg(feature = "printing")]
+                return Err(Error::new_spanned(first_ty_ref, "expected trait path"));
+                #[cfg(not(feature = "printing"))]
+                return Err(Error::new(first_ty_span, "expected trait path"));
+            } else {
+                trait_ = None;
+            }
+            self_ty = input.parse()?;
+        } else if let Some(polarity) = polarity {
+            return Err(Error::new(
+                polarity.span,
+                "inherent impls cannot be negative",
+            ));
+        } else {
+            trait_ = None;
+            self_ty = first_ty;
+        }
+
+        generics.where_clause = input.parse()?;
+
+        let content;
+        let brace_token = braced!(content in input);
+        attr::parsing::parse_inner(&content, &mut attrs)?;
+
+        let mut items = Vec::new();
+        while !content.is_empty() {
+            items.push(content.parse()?);
+        }
+
+        if has_visibility || is_const_impl || is_impl_for && trait_.is_none() {
+            Ok(None)
+        } else {
+            Ok(Some(ItemImpl {
+                attrs,
+                defaultness,
+                unsafety,
+                impl_token,
+                generics,
+                trait_,
+                self_ty: Box::new(self_ty),
+                brace_token,
+                items,
+            }))
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ImplItem {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let begin = input.fork();
+            let mut attrs = input.call(Attribute::parse_outer)?;
+            let ahead = input.fork();
+            let vis: Visibility = ahead.parse()?;
+
+            let mut lookahead = ahead.lookahead1();
+            let defaultness = if lookahead.peek(Token![default]) && !ahead.peek2(Token![!]) {
+                let defaultness: Token![default] = ahead.parse()?;
+                lookahead = ahead.lookahead1();
+                Some(defaultness)
+            } else {
+                None
+            };
+
+            let allow_safe = false;
+            let mut item = if lookahead.peek(Token![fn]) || peek_signature(&ahead, allow_safe) {
+                let allow_omitted_body = true;
+                if let Some(item) = parse_impl_item_fn(input, allow_omitted_body)? {
+                    Ok(ImplItem::Fn(item))
+                } else {
+                    Ok(ImplItem::Verbatim(verbatim::between(&begin, input)))
+                }
+            } else if lookahead.peek(Token![const]) {
+                input.advance_to(&ahead);
+                let const_token: Token![const] = input.parse()?;
+                let lookahead = input.lookahead1();
+                let ident = if lookahead.peek(Ident) || lookahead.peek(Token![_]) {
+                    input.call(Ident::parse_any)?
+                } else {
+                    return Err(lookahead.error());
+                };
+                let mut generics: Generics = input.parse()?;
+                let colon_token: Token![:] = input.parse()?;
+                let ty: Type = input.parse()?;
+                let value = if let Some(eq_token) = input.parse::<Option<Token![=]>>()? {
+                    let expr: Expr = input.parse()?;
+                    Some((eq_token, expr))
+                } else {
+                    None
+                };
+                generics.where_clause = input.parse()?;
+                let semi_token: Token![;] = input.parse()?;
+                return match value {
+                    Some((eq_token, expr))
+                        if generics.lt_token.is_none() && generics.where_clause.is_none() =>
+                    {
+                        Ok(ImplItem::Const(ImplItemConst {
+                            attrs,
+                            vis,
+                            defaultness,
+                            const_token,
+                            ident,
+                            generics,
+                            colon_token,
+                            ty,
+                            eq_token,
+                            expr,
+                            semi_token,
+                        }))
+                    }
+                    _ => Ok(ImplItem::Verbatim(verbatim::between(&begin, input))),
+                };
+            } else if lookahead.peek(Token![type]) {
+                parse_impl_item_type(begin, input)
+            } else if vis.is_inherited()
+                && defaultness.is_none()
+                && (lookahead.peek(Ident)
+                    || lookahead.peek(Token![self])
+                    || lookahead.peek(Token![super])
+                    || lookahead.peek(Token![crate])
+                    || lookahead.peek(Token![::]))
+            {
+                input.parse().map(ImplItem::Macro)
+            } else {
+                Err(lookahead.error())
+            }?;
+
+            {
+                let item_attrs = match &mut item {
+                    ImplItem::Const(item) => &mut item.attrs,
+                    ImplItem::Fn(item) => &mut item.attrs,
+                    ImplItem::Type(item) => &mut item.attrs,
+                    ImplItem::Macro(item) => &mut item.attrs,
+                    ImplItem::Verbatim(_) => return Ok(item),
+                };
+                attrs.append(item_attrs);
+                *item_attrs = attrs;
+            }
+
+            Ok(item)
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ImplItemConst {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let vis: Visibility = input.parse()?;
+            let defaultness: Option<Token![default]> = input.parse()?;
+            let const_token: Token![const] = input.parse()?;
+
+            let lookahead = input.lookahead1();
+            let ident = if lookahead.peek(Ident) || lookahead.peek(Token![_]) {
+                input.call(Ident::parse_any)?
+            } else {
+                return Err(lookahead.error());
+            };
+
+            let colon_token: Token![:] = input.parse()?;
+            let ty: Type = input.parse()?;
+            let eq_token: Token![=] = input.parse()?;
+            let expr: Expr = input.parse()?;
+            let semi_token: Token![;] = input.parse()?;
+
+            Ok(ImplItemConst {
+                attrs,
+                vis,
+                defaultness,
+                const_token,
+                ident,
+                generics: Generics::default(),
+                colon_token,
+                ty,
+                eq_token,
+                expr,
+                semi_token,
+            })
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ImplItemFn {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let allow_omitted_body = false;
+            parse_impl_item_fn(input, allow_omitted_body).map(Option::unwrap)
+        }
+    }
+
+    fn parse_impl_item_fn(
+        input: ParseStream,
+        allow_omitted_body: bool,
+    ) -> Result<Option<ImplItemFn>> {
+        let mut attrs = input.call(Attribute::parse_outer)?;
+        let vis: Visibility = input.parse()?;
+        let defaultness: Option<Token![default]> = input.parse()?;
+        let sig: Signature = input.parse()?;
+
+        // Accept functions without a body in an impl block because rustc's
+        // *parser* does not reject them (the compilation error is emitted later
+        // than parsing) and it can be useful for macro DSLs.
+        if allow_omitted_body && input.parse::<Option<Token![;]>>()?.is_some() {
+            return Ok(None);
+        }
+
+        let content;
+        let brace_token = braced!(content in input);
+        attrs.extend(content.call(Attribute::parse_inner)?);
+        let block = Block {
+            brace_token,
+            stmts: content.call(Block::parse_within)?,
+        };
+
+        Ok(Some(ImplItemFn {
+            attrs,
+            vis,
+            defaultness,
+            sig,
+            block,
+        }))
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ImplItemType {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let vis: Visibility = input.parse()?;
+            let defaultness: Option<Token![default]> = input.parse()?;
+            let type_token: Token![type] = input.parse()?;
+            let ident: Ident = input.parse()?;
+            let mut generics: Generics = input.parse()?;
+            let eq_token: Token![=] = input.parse()?;
+            let ty: Type = input.parse()?;
+            generics.where_clause = input.parse()?;
+            let semi_token: Token![;] = input.parse()?;
+            Ok(ImplItemType {
+                attrs,
+                vis,
+                defaultness,
+                type_token,
+                ident,
+                generics,
+                eq_token,
+                ty,
+                semi_token,
+            })
+        }
+    }
+
+    fn parse_impl_item_type(begin: ParseBuffer, input: ParseStream) -> Result<ImplItem> {
+        let FlexibleItemType {
+            vis,
+            defaultness,
+            type_token,
+            ident,
+            generics,
+            colon_token,
+            bounds: _,
+            ty,
+            semi_token,
+        } = FlexibleItemType::parse(
+            input,
+            TypeDefaultness::Optional,
+            WhereClauseLocation::AfterEq,
+        )?;
+
+        let (eq_token, ty) = match ty {
+            Some(ty) if colon_token.is_none() => ty,
+            _ => return Ok(ImplItem::Verbatim(verbatim::between(&begin, input))),
+        };
+
+        Ok(ImplItem::Type(ImplItemType {
+            attrs: Vec::new(),
+            vis,
+            defaultness,
+            type_token,
+            ident,
+            generics,
+            eq_token,
+            ty,
+            semi_token,
+        }))
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for ImplItemMacro {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let attrs = input.call(Attribute::parse_outer)?;
+            let mac: Macro = input.parse()?;
+            let semi_token: Option<Token![;]> = if mac.delimiter.is_brace() {
+                None
+            } else {
+                Some(input.parse()?)
+            };
+            Ok(ImplItemMacro {
+                attrs,
+                mac,
+                semi_token,
+            })
+        }
+    }
+
+    impl Visibility {
+        fn is_inherited(&self) -> bool {
+            match self {
+                Visibility::Inherited => true,
+                _ => false,
+            }
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for StaticMutability {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let mut_token: Option<Token![mut]> = input.parse()?;
+            Ok(mut_token.map_or(StaticMutability::None, StaticMutability::Mut))
+        }
+    }
+}
+
+#[cfg(feature = "printing")]
+mod printing {
+    use crate::attr::FilterAttrs;
+    use crate::data::Fields;
+    use crate::item::{
+        ForeignItemFn, ForeignItemMacro, ForeignItemStatic, ForeignItemType, ImplItemConst,
+        ImplItemFn, ImplItemMacro, ImplItemType, ItemConst, ItemEnum, ItemExternCrate, ItemFn,
+        ItemForeignMod, ItemImpl, ItemMacro, ItemMod, ItemStatic, ItemStruct, ItemTrait,
+        ItemTraitAlias, ItemType, ItemUnion, ItemUse, Receiver, Signature, StaticMutability,
+        TraitItemConst, TraitItemFn, TraitItemMacro, TraitItemType, UseGlob, UseGroup, UseName,
+        UsePath, UseRename, Variadic,
+    };
+    use crate::mac::MacroDelimiter;
+    use crate::path;
+    use crate::path::printing::PathStyle;
+    use crate::print::TokensOrDefault;
+    use crate::ty::Type;
+    use proc_macro2::TokenStream;
+    use quote::{ToTokens, TokenStreamExt};
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemExternCrate {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.extern_token.to_tokens(tokens);
+            self.crate_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            if let Some((as_token, rename)) = &self.rename {
+                as_token.to_tokens(tokens);
+                rename.to_tokens(tokens);
+            }
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemUse {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.use_token.to_tokens(tokens);
+            self.leading_colon.to_tokens(tokens);
+            self.tree.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemStatic {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.static_token.to_tokens(tokens);
+            self.mutability.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.colon_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemConst {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.const_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.colon_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemFn {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.sig.to_tokens(tokens);
+            self.block.brace_token.surround(tokens, |tokens| {
+                tokens.append_all(self.attrs.inner());
+                tokens.append_all(&self.block.stmts);
+            });
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemMod {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.unsafety.to_tokens(tokens);
+            self.mod_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            if let Some((brace, items)) = &self.content {
+                brace.surround(tokens, |tokens| {
+                    tokens.append_all(self.attrs.inner());
+                    tokens.append_all(items);
+                });
+            } else {
+                TokensOrDefault(&self.semi).to_tokens(tokens);
+            }
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemForeignMod {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.unsafety.to_tokens(tokens);
+            self.abi.to_tokens(tokens);
+            self.brace_token.surround(tokens, |tokens| {
+                tokens.append_all(self.attrs.inner());
+                tokens.append_all(&self.items);
+            });
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemType {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.type_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            self.generics.where_clause.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemEnum {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.enum_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            self.generics.where_clause.to_tokens(tokens);
+            self.brace_token.surround(tokens, |tokens| {
+                self.variants.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemStruct {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.struct_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            match &self.fields {
+                Fields::Named(fields) => {
+                    self.generics.where_clause.to_tokens(tokens);
+                    fields.to_tokens(tokens);
+                }
+                Fields::Unnamed(fields) => {
+                    fields.to_tokens(tokens);
+                    self.generics.where_clause.to_tokens(tokens);
+                    TokensOrDefault(&self.semi_token).to_tokens(tokens);
+                }
+                Fields::Unit => {
+                    self.generics.where_clause.to_tokens(tokens);
+                    TokensOrDefault(&self.semi_token).to_tokens(tokens);
+                }
+            }
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemUnion {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.union_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            self.generics.where_clause.to_tokens(tokens);
+            self.fields.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemTrait {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.unsafety.to_tokens(tokens);
+            self.auto_token.to_tokens(tokens);
+            self.trait_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            if !self.supertraits.is_empty() {
+                TokensOrDefault(&self.colon_token).to_tokens(tokens);
+                self.supertraits.to_tokens(tokens);
+            }
+            self.generics.where_clause.to_tokens(tokens);
+            self.brace_token.surround(tokens, |tokens| {
+                tokens.append_all(self.attrs.inner());
+                tokens.append_all(&self.items);
+            });
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemTraitAlias {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.trait_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            self.bounds.to_tokens(tokens);
+            self.generics.where_clause.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemImpl {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.defaultness.to_tokens(tokens);
+            self.unsafety.to_tokens(tokens);
+            self.impl_token.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            if let Some((polarity, path, for_token)) = &self.trait_ {
+                polarity.to_tokens(tokens);
+                path.to_tokens(tokens);
+                for_token.to_tokens(tokens);
+            }
+            self.self_ty.to_tokens(tokens);
+            self.generics.where_clause.to_tokens(tokens);
+            self.brace_token.surround(tokens, |tokens| {
+                tokens.append_all(self.attrs.inner());
+                tokens.append_all(&self.items);
+            });
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ItemMacro {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            path::printing::print_path(tokens, &self.mac.path, PathStyle::Mod);
+            self.mac.bang_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            match &self.mac.delimiter {
+                MacroDelimiter::Paren(paren) => {
+                    paren.surround(tokens, |tokens| self.mac.tokens.to_tokens(tokens));
+                }
+                MacroDelimiter::Brace(brace) => {
+                    brace.surround(tokens, |tokens| self.mac.tokens.to_tokens(tokens));
+                }
+                MacroDelimiter::Bracket(bracket) => {
+                    bracket.surround(tokens, |tokens| self.mac.tokens.to_tokens(tokens));
+                }
+            }
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for UsePath {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.ident.to_tokens(tokens);
+            self.colon2_token.to_tokens(tokens);
+            self.tree.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for UseName {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.ident.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for UseRename {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.ident.to_tokens(tokens);
+            self.as_token.to_tokens(tokens);
+            self.rename.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for UseGlob {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.star_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for UseGroup {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.brace_token.surround(tokens, |tokens| {
+                self.items.to_tokens(tokens);
+            });
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for TraitItemConst {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.const_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.colon_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+            if let Some((eq_token, default)) = &self.default {
+                eq_token.to_tokens(tokens);
+                default.to_tokens(tokens);
+            }
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for TraitItemFn {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.sig.to_tokens(tokens);
+            match &self.default {
+                Some(block) => {
+                    block.brace_token.surround(tokens, |tokens| {
+                        tokens.append_all(self.attrs.inner());
+                        tokens.append_all(&block.stmts);
+                    });
+                }
+                None => {
+                    TokensOrDefault(&self.semi_token).to_tokens(tokens);
+                }
+            }
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for TraitItemType {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.type_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            if !self.bounds.is_empty() {
+                TokensOrDefault(&self.colon_token).to_tokens(tokens);
+                self.bounds.to_tokens(tokens);
+            }
+            if let Some((eq_token, default)) = &self.default {
+                eq_token.to_tokens(tokens);
+                default.to_tokens(tokens);
+            }
+            self.generics.where_clause.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for TraitItemMacro {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.mac.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ImplItemConst {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.defaultness.to_tokens(tokens);
+            self.const_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.colon_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            self.expr.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ImplItemFn {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.defaultness.to_tokens(tokens);
+            self.sig.to_tokens(tokens);
+            self.block.brace_token.surround(tokens, |tokens| {
+                tokens.append_all(self.attrs.inner());
+                tokens.append_all(&self.block.stmts);
+            });
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ImplItemType {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.defaultness.to_tokens(tokens);
+            self.type_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            self.eq_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+            self.generics.where_clause.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ImplItemMacro {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.mac.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ForeignItemFn {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.sig.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ForeignItemStatic {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.static_token.to_tokens(tokens);
+            self.mutability.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.colon_token.to_tokens(tokens);
+            self.ty.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ForeignItemType {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.vis.to_tokens(tokens);
+            self.type_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            self.generics.where_clause.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for ForeignItemMacro {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            self.mac.to_tokens(tokens);
+            self.semi_token.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for Signature {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            self.constness.to_tokens(tokens);
+            self.asyncness.to_tokens(tokens);
+            self.unsafety.to_tokens(tokens);
+            self.abi.to_tokens(tokens);
+            self.fn_token.to_tokens(tokens);
+            self.ident.to_tokens(tokens);
+            self.generics.to_tokens(tokens);
+            self.paren_token.surround(tokens, |tokens| {
+                self.inputs.to_tokens(tokens);
+                if let Some(variadic) = &self.variadic {
+                    if !self.inputs.empty_or_trailing() {
+                        <Token![,]>::default().to_tokens(tokens);
+                    }
+                    variadic.to_tokens(tokens);
+                }
+            });
+            self.output.to_tokens(tokens);
+            self.generics.where_clause.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for Receiver {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            if let Some((ampersand, lifetime)) = &self.reference {
+                ampersand.to_tokens(tokens);
+                lifetime.to_tokens(tokens);
+            }
+            self.mutability.to_tokens(tokens);
+            self.self_token.to_tokens(tokens);
+            if let Some(colon_token) = &self.colon_token {
+                colon_token.to_tokens(tokens);
+                self.ty.to_tokens(tokens);
+            } else {
+                let consistent = match (&self.reference, &self.mutability, &*self.ty) {
+                    (Some(_), mutability, Type::Reference(ty)) => {
+                        mutability.is_some() == ty.mutability.is_some()
+                            && match &*ty.elem {
+                                Type::Path(ty) => ty.qself.is_none() && ty.path.is_ident("Self"),
+                                _ => false,
+                            }
+                    }
+                    (None, _, Type::Path(ty)) => ty.qself.is_none() && ty.path.is_ident("Self"),
+                    _ => false,
+                };
+                if !consistent {
+                    <Token![:]>::default().to_tokens(tokens);
+                    self.ty.to_tokens(tokens);
+                }
+            }
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for Variadic {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            tokens.append_all(self.attrs.outer());
+            if let Some((pat, colon)) = &self.pat {
+                pat.to_tokens(tokens);
+                colon.to_tokens(tokens);
+            }
+            self.dots.to_tokens(tokens);
+            self.comma.to_tokens(tokens);
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "printing")))]
+    impl ToTokens for StaticMutability {
+        fn to_tokens(&self, tokens: &mut TokenStream) {
+            match self {
+                StaticMutability::None => {}
+                StaticMutability::Mut(mut_token) => mut_token.to_tokens(tokens),
+            }
+        }
+    }
+}