Adding upstream version 124.0.1.upstream/124.0.1

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

38 files changed, 12382 insertions, 0 deletions

diff --git a/third_party/rust/syn/tests/common/eq.rs b/third_party/rust/syn/tests/common/eq.rs
new file mode 100644
index 0000000000..8ecbe46a36
--- /dev/null
+++ b/third_party/rust/syn/tests/common/eq.rs
@@ -0,0 +1,879 @@
+#![allow(unused_macro_rules)]
+
+extern crate rustc_ast;
+extern crate rustc_data_structures;
+extern crate rustc_driver;
+extern crate rustc_span;
+extern crate thin_vec;
+
+use rustc_ast::ast::AngleBracketedArg;
+use rustc_ast::ast::AngleBracketedArgs;
+use rustc_ast::ast::AnonConst;
+use rustc_ast::ast::Arm;
+use rustc_ast::ast::AssocConstraint;
+use rustc_ast::ast::AssocConstraintKind;
+use rustc_ast::ast::AssocItemKind;
+use rustc_ast::ast::AttrArgs;
+use rustc_ast::ast::AttrArgsEq;
+use rustc_ast::ast::AttrId;
+use rustc_ast::ast::AttrItem;
+use rustc_ast::ast::AttrKind;
+use rustc_ast::ast::AttrStyle;
+use rustc_ast::ast::Attribute;
+use rustc_ast::ast::BareFnTy;
+use rustc_ast::ast::BinOpKind;
+use rustc_ast::ast::BindingAnnotation;
+use rustc_ast::ast::Block;
+use rustc_ast::ast::BlockCheckMode;
+use rustc_ast::ast::BorrowKind;
+use rustc_ast::ast::BoundConstness;
+use rustc_ast::ast::BoundPolarity;
+use rustc_ast::ast::ByRef;
+use rustc_ast::ast::CaptureBy;
+use rustc_ast::ast::Closure;
+use rustc_ast::ast::ClosureBinder;
+use rustc_ast::ast::Const;
+use rustc_ast::ast::ConstItem;
+use rustc_ast::ast::CoroutineKind;
+use rustc_ast::ast::Crate;
+use rustc_ast::ast::Defaultness;
+use rustc_ast::ast::DelimArgs;
+use rustc_ast::ast::EnumDef;
+use rustc_ast::ast::Expr;
+use rustc_ast::ast::ExprField;
+use rustc_ast::ast::ExprKind;
+use rustc_ast::ast::Extern;
+use rustc_ast::ast::FieldDef;
+use rustc_ast::ast::FloatTy;
+use rustc_ast::ast::Fn;
+use rustc_ast::ast::FnDecl;
+use rustc_ast::ast::FnHeader;
+use rustc_ast::ast::FnRetTy;
+use rustc_ast::ast::FnSig;
+use rustc_ast::ast::ForLoopKind;
+use rustc_ast::ast::ForeignItemKind;
+use rustc_ast::ast::ForeignMod;
+use rustc_ast::ast::FormatAlignment;
+use rustc_ast::ast::FormatArgPosition;
+use rustc_ast::ast::FormatArgPositionKind;
+use rustc_ast::ast::FormatArgs;
+use rustc_ast::ast::FormatArgsPiece;
+use rustc_ast::ast::FormatArgument;
+use rustc_ast::ast::FormatArgumentKind;
+use rustc_ast::ast::FormatArguments;
+use rustc_ast::ast::FormatCount;
+use rustc_ast::ast::FormatDebugHex;
+use rustc_ast::ast::FormatOptions;
+use rustc_ast::ast::FormatPlaceholder;
+use rustc_ast::ast::FormatSign;
+use rustc_ast::ast::FormatTrait;
+use rustc_ast::ast::GenBlockKind;
+use rustc_ast::ast::GenericArg;
+use rustc_ast::ast::GenericArgs;
+use rustc_ast::ast::GenericBound;
+use rustc_ast::ast::GenericParam;
+use rustc_ast::ast::GenericParamKind;
+use rustc_ast::ast::Generics;
+use rustc_ast::ast::Impl;
+use rustc_ast::ast::ImplPolarity;
+use rustc_ast::ast::Inline;
+use rustc_ast::ast::InlineAsm;
+use rustc_ast::ast::InlineAsmOperand;
+use rustc_ast::ast::InlineAsmOptions;
+use rustc_ast::ast::InlineAsmRegOrRegClass;
+use rustc_ast::ast::InlineAsmSym;
+use rustc_ast::ast::InlineAsmTemplatePiece;
+use rustc_ast::ast::IntTy;
+use rustc_ast::ast::IsAuto;
+use rustc_ast::ast::Item;
+use rustc_ast::ast::ItemKind;
+use rustc_ast::ast::Label;
+use rustc_ast::ast::Lifetime;
+use rustc_ast::ast::LitFloatType;
+use rustc_ast::ast::LitIntType;
+use rustc_ast::ast::LitKind;
+use rustc_ast::ast::Local;
+use rustc_ast::ast::LocalKind;
+use rustc_ast::ast::MacCall;
+use rustc_ast::ast::MacCallStmt;
+use rustc_ast::ast::MacStmtStyle;
+use rustc_ast::ast::MacroDef;
+use rustc_ast::ast::MetaItemLit;
+use rustc_ast::ast::MethodCall;
+use rustc_ast::ast::ModKind;
+use rustc_ast::ast::ModSpans;
+use rustc_ast::ast::Movability;
+use rustc_ast::ast::MutTy;
+use rustc_ast::ast::Mutability;
+use rustc_ast::ast::NodeId;
+use rustc_ast::ast::NormalAttr;
+use rustc_ast::ast::Param;
+use rustc_ast::ast::ParenthesizedArgs;
+use rustc_ast::ast::Pat;
+use rustc_ast::ast::PatField;
+use rustc_ast::ast::PatFieldsRest;
+use rustc_ast::ast::PatKind;
+use rustc_ast::ast::Path;
+use rustc_ast::ast::PathSegment;
+use rustc_ast::ast::PolyTraitRef;
+use rustc_ast::ast::QSelf;
+use rustc_ast::ast::RangeEnd;
+use rustc_ast::ast::RangeLimits;
+use rustc_ast::ast::RangeSyntax;
+use rustc_ast::ast::StaticItem;
+use rustc_ast::ast::Stmt;
+use rustc_ast::ast::StmtKind;
+use rustc_ast::ast::StrLit;
+use rustc_ast::ast::StrStyle;
+use rustc_ast::ast::StructExpr;
+use rustc_ast::ast::StructRest;
+use rustc_ast::ast::Term;
+use rustc_ast::ast::Trait;
+use rustc_ast::ast::TraitBoundModifiers;
+use rustc_ast::ast::TraitObjectSyntax;
+use rustc_ast::ast::TraitRef;
+use rustc_ast::ast::Ty;
+use rustc_ast::ast::TyAlias;
+use rustc_ast::ast::TyAliasWhereClause;
+use rustc_ast::ast::TyKind;
+use rustc_ast::ast::UintTy;
+use rustc_ast::ast::UnOp;
+use rustc_ast::ast::Unsafe;
+use rustc_ast::ast::UnsafeSource;
+use rustc_ast::ast::UseTree;
+use rustc_ast::ast::UseTreeKind;
+use rustc_ast::ast::Variant;
+use rustc_ast::ast::VariantData;
+use rustc_ast::ast::Visibility;
+use rustc_ast::ast::VisibilityKind;
+use rustc_ast::ast::WhereBoundPredicate;
+use rustc_ast::ast::WhereClause;
+use rustc_ast::ast::WhereEqPredicate;
+use rustc_ast::ast::WherePredicate;
+use rustc_ast::ast::WhereRegionPredicate;
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, CommentKind, Delimiter, Lit, Nonterminal, Token, TokenKind};
+use rustc_ast::tokenstream::{
+    AttrTokenStream, AttrTokenTree, AttributesData, DelimSpacing, DelimSpan, LazyAttrTokenStream,
+    Spacing, TokenStream, TokenTree,
+};
+use rustc_data_structures::sync::Lrc;
+use rustc_span::source_map::Spanned;
+use rustc_span::symbol::{sym, Ident};
+use rustc_span::{ErrorGuaranteed, Span, Symbol, SyntaxContext, DUMMY_SP};
+use std::collections::HashMap;
+use std::hash::{BuildHasher, Hash};
+use thin_vec::ThinVec;
+
+pub trait SpanlessEq {
+    fn eq(&self, other: &Self) -> bool;
+}
+
+impl<T: ?Sized + SpanlessEq> SpanlessEq for Box<T> {
+    fn eq(&self, other: &Self) -> bool {
+        SpanlessEq::eq(&**self, &**other)
+    }
+}
+
+impl<T: ?Sized + SpanlessEq> SpanlessEq for P<T> {
+    fn eq(&self, other: &Self) -> bool {
+        SpanlessEq::eq(&**self, &**other)
+    }
+}
+
+impl<T: ?Sized + SpanlessEq> SpanlessEq for Lrc<T> {
+    fn eq(&self, other: &Self) -> bool {
+        SpanlessEq::eq(&**self, &**other)
+    }
+}
+
+impl<T: SpanlessEq> SpanlessEq for Option<T> {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (None, None) => true,
+            (Some(this), Some(other)) => SpanlessEq::eq(this, other),
+            _ => false,
+        }
+    }
+}
+
+impl<T: SpanlessEq, E: SpanlessEq> SpanlessEq for Result<T, E> {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Ok(this), Ok(other)) => SpanlessEq::eq(this, other),
+            (Err(this), Err(other)) => SpanlessEq::eq(this, other),
+            _ => false,
+        }
+    }
+}
+
+impl<T: SpanlessEq> SpanlessEq for [T] {
+    fn eq(&self, other: &Self) -> bool {
+        self.len() == other.len() && self.iter().zip(other).all(|(a, b)| SpanlessEq::eq(a, b))
+    }
+}
+
+impl<T: SpanlessEq> SpanlessEq for Vec<T> {
+    fn eq(&self, other: &Self) -> bool {
+        <[T] as SpanlessEq>::eq(self, other)
+    }
+}
+
+impl<T: SpanlessEq> SpanlessEq for ThinVec<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.len() == other.len()
+            && self
+                .iter()
+                .zip(other.iter())
+                .all(|(a, b)| SpanlessEq::eq(a, b))
+    }
+}
+
+impl<K: Eq + Hash, V: SpanlessEq, S: BuildHasher> SpanlessEq for HashMap<K, V, S> {
+    fn eq(&self, other: &Self) -> bool {
+        self.len() == other.len()
+            && self.iter().all(|(key, this_v)| {
+                other
+                    .get(key)
+                    .map_or(false, |other_v| SpanlessEq::eq(this_v, other_v))
+            })
+    }
+}
+
+impl<T: SpanlessEq> SpanlessEq for Spanned<T> {
+    fn eq(&self, other: &Self) -> bool {
+        SpanlessEq::eq(&self.node, &other.node)
+    }
+}
+
+impl<A: SpanlessEq, B: SpanlessEq> SpanlessEq for (A, B) {
+    fn eq(&self, other: &Self) -> bool {
+        SpanlessEq::eq(&self.0, &other.0) && SpanlessEq::eq(&self.1, &other.1)
+    }
+}
+
+impl<A: SpanlessEq, B: SpanlessEq, C: SpanlessEq> SpanlessEq for (A, B, C) {
+    fn eq(&self, other: &Self) -> bool {
+        SpanlessEq::eq(&self.0, &other.0)
+            && SpanlessEq::eq(&self.1, &other.1)
+            && SpanlessEq::eq(&self.2, &other.2)
+    }
+}
+
+macro_rules! spanless_eq_true {
+    ($name:ty) => {
+        impl SpanlessEq for $name {
+            fn eq(&self, _other: &Self) -> bool {
+                true
+            }
+        }
+    };
+}
+
+spanless_eq_true!(Span);
+spanless_eq_true!(DelimSpan);
+spanless_eq_true!(AttrId);
+spanless_eq_true!(NodeId);
+spanless_eq_true!(SyntaxContext);
+spanless_eq_true!(Spacing);
+
+macro_rules! spanless_eq_partial_eq {
+    ($name:ty) => {
+        impl SpanlessEq for $name {
+            fn eq(&self, other: &Self) -> bool {
+                PartialEq::eq(self, other)
+            }
+        }
+    };
+}
+
+spanless_eq_partial_eq!(bool);
+spanless_eq_partial_eq!(u8);
+spanless_eq_partial_eq!(u16);
+spanless_eq_partial_eq!(u32);
+spanless_eq_partial_eq!(u128);
+spanless_eq_partial_eq!(usize);
+spanless_eq_partial_eq!(char);
+spanless_eq_partial_eq!(String);
+spanless_eq_partial_eq!(Symbol);
+spanless_eq_partial_eq!(CommentKind);
+spanless_eq_partial_eq!(Delimiter);
+spanless_eq_partial_eq!(InlineAsmOptions);
+spanless_eq_partial_eq!(token::LitKind);
+spanless_eq_partial_eq!(ErrorGuaranteed);
+
+macro_rules! spanless_eq_struct {
+    {
+        $($name:ident)::+ $(<$param:ident>)?
+        $([$field:tt $this:ident $other:ident])*
+        $(![$ignore:tt])*;
+    } => {
+        impl $(<$param: SpanlessEq>)* SpanlessEq for $($name)::+ $(<$param>)* {
+            fn eq(&self, other: &Self) -> bool {
+                let $($name)::+ { $($field: $this,)* $($ignore: _,)* } = self;
+                let $($name)::+ { $($field: $other,)* $($ignore: _,)* } = other;
+                true $(&& SpanlessEq::eq($this, $other))*
+            }
+        }
+    };
+
+    {
+        $($name:ident)::+ $(<$param:ident>)?
+        $([$field:tt $this:ident $other:ident])*
+        $(![$ignore:tt])*;
+        !$next:tt
+        $($rest:tt)*
+    } => {
+        spanless_eq_struct! {
+            $($name)::+ $(<$param>)*
+            $([$field $this $other])*
+            $(![$ignore])*
+            ![$next];
+            $($rest)*
+        }
+    };
+
+    {
+        $($name:ident)::+ $(<$param:ident>)?
+        $([$field:tt $this:ident $other:ident])*
+        $(![$ignore:tt])*;
+        $next:tt
+        $($rest:tt)*
+    } => {
+        spanless_eq_struct! {
+            $($name)::+ $(<$param>)*
+            $([$field $this $other])*
+            [$next this other]
+            $(![$ignore])*;
+            $($rest)*
+        }
+    };
+}
+
+macro_rules! spanless_eq_enum {
+    {
+        $($name:ident)::+;
+        $([$($variant:ident)::+; $([$field:tt $this:ident $other:ident])* $(![$ignore:tt])*])*
+    } => {
+        impl SpanlessEq for $($name)::+ {
+            fn eq(&self, other: &Self) -> bool {
+                match self {
+                    $(
+                        $($variant)::+ { .. } => {}
+                    )*
+                }
+                #[allow(unreachable_patterns)]
+                match (self, other) {
+                    $(
+                        (
+                            $($variant)::+ { $($field: $this,)* $($ignore: _,)* },
+                            $($variant)::+ { $($field: $other,)* $($ignore: _,)* },
+                        ) => {
+                            true $(&& SpanlessEq::eq($this, $other))*
+                        }
+                    )*
+                    _ => false,
+                }
+            }
+        }
+    };
+
+    {
+        $($name:ident)::+;
+        $([$($variant:ident)::+; $($fields:tt)*])*
+        $next:ident [$([$($named:tt)*])* $(![$ignore:tt])*] (!$i:tt $($field:tt)*)
+        $($rest:tt)*
+    } => {
+        spanless_eq_enum! {
+            $($name)::+;
+            $([$($variant)::+; $($fields)*])*
+            $next [$([$($named)*])* $(![$ignore])* ![$i]] ($($field)*)
+            $($rest)*
+        }
+    };
+
+    {
+        $($name:ident)::+;
+        $([$($variant:ident)::+; $($fields:tt)*])*
+        $next:ident [$([$($named:tt)*])* $(![$ignore:tt])*] ($i:tt $($field:tt)*)
+        $($rest:tt)*
+    } => {
+        spanless_eq_enum! {
+            $($name)::+;
+            $([$($variant)::+; $($fields)*])*
+            $next [$([$($named)*])* [$i this other] $(![$ignore])*] ($($field)*)
+            $($rest)*
+        }
+    };
+
+    {
+        $($name:ident)::+;
+        $([$($variant:ident)::+; $($fields:tt)*])*
+        $next:ident [$($named:tt)*] ()
+        $($rest:tt)*
+    } => {
+        spanless_eq_enum! {
+            $($name)::+;
+            $([$($variant)::+; $($fields)*])*
+            [$($name)::+::$next; $($named)*]
+            $($rest)*
+        }
+    };
+
+    {
+        $($name:ident)::+;
+        $([$($variant:ident)::+; $($fields:tt)*])*
+        $next:ident ($($field:tt)*)
+        $($rest:tt)*
+    } => {
+        spanless_eq_enum! {
+            $($name)::+;
+            $([$($variant)::+; $($fields)*])*
+            $next [] ($($field)*)
+            $($rest)*
+        }
+    };
+
+    {
+        $($name:ident)::+;
+        $([$($variant:ident)::+; $($fields:tt)*])*
+        $next:ident
+        $($rest:tt)*
+    } => {
+        spanless_eq_enum! {
+            $($name)::+;
+            $([$($variant)::+; $($fields)*])*
+            [$($name)::+::$next;]
+            $($rest)*
+        }
+    };
+}
+
+spanless_eq_struct!(AngleBracketedArgs; span args);
+spanless_eq_struct!(AnonConst; id value);
+spanless_eq_struct!(Arm; attrs pat guard body span id is_placeholder);
+spanless_eq_struct!(AssocConstraint; id ident gen_args kind span);
+spanless_eq_struct!(AttrItem; path args tokens);
+spanless_eq_struct!(AttrTokenStream; 0);
+spanless_eq_struct!(Attribute; kind id style span);
+spanless_eq_struct!(AttributesData; attrs tokens);
+spanless_eq_struct!(BareFnTy; unsafety ext generic_params decl decl_span);
+spanless_eq_struct!(BindingAnnotation; 0 1);
+spanless_eq_struct!(Block; stmts id rules span tokens could_be_bare_literal);
+spanless_eq_struct!(Closure; binder capture_clause constness coroutine_kind movability fn_decl body !fn_decl_span !fn_arg_span);
+spanless_eq_struct!(ConstItem; defaultness generics ty expr);
+spanless_eq_struct!(Crate; attrs items spans id is_placeholder);
+spanless_eq_struct!(DelimArgs; dspan delim tokens);
+spanless_eq_struct!(DelimSpacing; open close);
+spanless_eq_struct!(EnumDef; variants);
+spanless_eq_struct!(Expr; id kind span attrs !tokens);
+spanless_eq_struct!(ExprField; attrs id span ident expr is_shorthand is_placeholder);
+spanless_eq_struct!(FieldDef; attrs id span vis ident ty is_placeholder);
+spanless_eq_struct!(Fn; defaultness generics sig body);
+spanless_eq_struct!(FnDecl; inputs output);
+spanless_eq_struct!(FnHeader; constness coroutine_kind unsafety ext);
+spanless_eq_struct!(FnSig; header decl span);
+spanless_eq_struct!(ForeignMod; unsafety abi items);
+spanless_eq_struct!(FormatArgPosition; index kind span);
+spanless_eq_struct!(FormatArgs; span template arguments);
+spanless_eq_struct!(FormatArgument; kind expr);
+spanless_eq_struct!(FormatOptions; width precision alignment fill sign alternate zero_pad debug_hex);
+spanless_eq_struct!(FormatPlaceholder; argument span format_trait format_options);
+spanless_eq_struct!(GenericParam; id ident attrs bounds is_placeholder kind !colon_span);
+spanless_eq_struct!(Generics; params where_clause span);
+spanless_eq_struct!(Impl; defaultness unsafety generics constness polarity of_trait self_ty items);
+spanless_eq_struct!(InlineAsm; template template_strs operands clobber_abis options line_spans);
+spanless_eq_struct!(InlineAsmSym; id qself path);
+spanless_eq_struct!(Item<K>; attrs id span vis ident kind !tokens);
+spanless_eq_struct!(Label; ident);
+spanless_eq_struct!(Lifetime; id ident);
+spanless_eq_struct!(Lit; kind symbol suffix);
+spanless_eq_struct!(Local; pat ty kind id span attrs !tokens);
+spanless_eq_struct!(MacCall; path args);
+spanless_eq_struct!(MacCallStmt; mac style attrs tokens);
+spanless_eq_struct!(MacroDef; body macro_rules);
+spanless_eq_struct!(MetaItemLit; symbol suffix kind span);
+spanless_eq_struct!(MethodCall; seg receiver args !span);
+spanless_eq_struct!(ModSpans; !inner_span !inject_use_span);
+spanless_eq_struct!(MutTy; ty mutbl);
+spanless_eq_struct!(NormalAttr; item tokens);
+spanless_eq_struct!(ParenthesizedArgs; span inputs inputs_span output);
+spanless_eq_struct!(Pat; id kind span tokens);
+spanless_eq_struct!(PatField; ident pat is_shorthand attrs id span is_placeholder);
+spanless_eq_struct!(Path; span segments tokens);
+spanless_eq_struct!(PathSegment; ident id args);
+spanless_eq_struct!(PolyTraitRef; bound_generic_params trait_ref span);
+spanless_eq_struct!(QSelf; ty path_span position);
+spanless_eq_struct!(StaticItem; ty mutability expr);
+spanless_eq_struct!(Stmt; id kind span);
+spanless_eq_struct!(StrLit; symbol suffix symbol_unescaped style span);
+spanless_eq_struct!(StructExpr; qself path fields rest);
+spanless_eq_struct!(Token; kind span);
+spanless_eq_struct!(Trait; unsafety is_auto generics bounds items);
+spanless_eq_struct!(TraitBoundModifiers; constness polarity);
+spanless_eq_struct!(TraitRef; path ref_id);
+spanless_eq_struct!(Ty; id kind span tokens);
+spanless_eq_struct!(TyAlias; defaultness generics where_clauses !where_predicates_split bounds ty);
+spanless_eq_struct!(TyAliasWhereClause; !0 1);
+spanless_eq_struct!(UseTree; prefix kind span);
+spanless_eq_struct!(Variant; attrs id span !vis ident data disr_expr is_placeholder);
+spanless_eq_struct!(Visibility; kind span tokens);
+spanless_eq_struct!(WhereBoundPredicate; span bound_generic_params bounded_ty bounds);
+spanless_eq_struct!(WhereClause; has_where_token predicates span);
+spanless_eq_struct!(WhereEqPredicate; span lhs_ty rhs_ty);
+spanless_eq_struct!(WhereRegionPredicate; span lifetime bounds);
+spanless_eq_enum!(AngleBracketedArg; Arg(0) Constraint(0));
+spanless_eq_enum!(AssocConstraintKind; Equality(term) Bound(bounds));
+spanless_eq_enum!(AssocItemKind; Const(0) Fn(0) Type(0) MacCall(0));
+spanless_eq_enum!(AttrArgs; Empty Delimited(0) Eq(0 1));
+spanless_eq_enum!(AttrArgsEq; Ast(0) Hir(0));
+spanless_eq_enum!(AttrStyle; Outer Inner);
+spanless_eq_enum!(AttrTokenTree; Token(0 1) Delimited(0 1 2 3) Attributes(0));
+spanless_eq_enum!(BinOpKind; Add Sub Mul Div Rem And Or BitXor BitAnd BitOr Shl Shr Eq Lt Le Ne Ge Gt);
+spanless_eq_enum!(BlockCheckMode; Default Unsafe(0));
+spanless_eq_enum!(BorrowKind; Ref Raw);
+spanless_eq_enum!(BoundConstness; Never Always(0) Maybe(0));
+spanless_eq_enum!(BoundPolarity; Positive Negative(0) Maybe(0));
+spanless_eq_enum!(ByRef; Yes No);
+spanless_eq_enum!(CaptureBy; Value(move_kw) Ref);
+spanless_eq_enum!(ClosureBinder; NotPresent For(span generic_params));
+spanless_eq_enum!(Const; Yes(0) No);
+spanless_eq_enum!(Defaultness; Default(0) Final);
+spanless_eq_enum!(Extern; None Implicit(0) Explicit(0 1));
+spanless_eq_enum!(FloatTy; F32 F64);
+spanless_eq_enum!(FnRetTy; Default(0) Ty(0));
+spanless_eq_enum!(ForLoopKind; For ForAwait);
+spanless_eq_enum!(ForeignItemKind; Static(0 1 2) Fn(0) TyAlias(0) MacCall(0));
+spanless_eq_enum!(FormatAlignment; Left Right Center);
+spanless_eq_enum!(FormatArgPositionKind; Implicit Number Named);
+spanless_eq_enum!(FormatArgsPiece; Literal(0) Placeholder(0));
+spanless_eq_enum!(FormatArgumentKind; Normal Named(0) Captured(0));
+spanless_eq_enum!(FormatCount; Literal(0) Argument(0));
+spanless_eq_enum!(FormatDebugHex; Lower Upper);
+spanless_eq_enum!(FormatSign; Plus Minus);
+spanless_eq_enum!(FormatTrait; Display Debug LowerExp UpperExp Octal Pointer Binary LowerHex UpperHex);
+spanless_eq_enum!(GenBlockKind; Async Gen AsyncGen);
+spanless_eq_enum!(GenericArg; Lifetime(0) Type(0) Const(0));
+spanless_eq_enum!(GenericArgs; AngleBracketed(0) Parenthesized(0));
+spanless_eq_enum!(GenericBound; Trait(0 1) Outlives(0));
+spanless_eq_enum!(GenericParamKind; Lifetime Type(default) Const(ty kw_span default));
+spanless_eq_enum!(ImplPolarity; Positive Negative(0));
+spanless_eq_enum!(Inline; Yes No);
+spanless_eq_enum!(InlineAsmRegOrRegClass; Reg(0) RegClass(0));
+spanless_eq_enum!(InlineAsmTemplatePiece; String(0) Placeholder(operand_idx modifier span));
+spanless_eq_enum!(IntTy; Isize I8 I16 I32 I64 I128);
+spanless_eq_enum!(IsAuto; Yes No);
+spanless_eq_enum!(LitFloatType; Suffixed(0) Unsuffixed);
+spanless_eq_enum!(LitIntType; Signed(0) Unsigned(0) Unsuffixed);
+spanless_eq_enum!(LocalKind; Decl Init(0) InitElse(0 1));
+spanless_eq_enum!(MacStmtStyle; Semicolon Braces NoBraces);
+spanless_eq_enum!(ModKind; Loaded(0 1 2) Unloaded);
+spanless_eq_enum!(Movability; Static Movable);
+spanless_eq_enum!(Mutability; Mut Not);
+spanless_eq_enum!(PatFieldsRest; Rest None);
+spanless_eq_enum!(RangeEnd; Included(0) Excluded);
+spanless_eq_enum!(RangeLimits; HalfOpen Closed);
+spanless_eq_enum!(StmtKind; Local(0) Item(0) Expr(0) Semi(0) Empty MacCall(0));
+spanless_eq_enum!(StrStyle; Cooked Raw(0));
+spanless_eq_enum!(StructRest; Base(0) Rest(0) None);
+spanless_eq_enum!(Term; Ty(0) Const(0));
+spanless_eq_enum!(TokenTree; Token(0 1) Delimited(0 1 2 3));
+spanless_eq_enum!(TraitObjectSyntax; Dyn DynStar None);
+spanless_eq_enum!(UintTy; Usize U8 U16 U32 U64 U128);
+spanless_eq_enum!(UnOp; Deref Not Neg);
+spanless_eq_enum!(Unsafe; Yes(0) No);
+spanless_eq_enum!(UnsafeSource; CompilerGenerated UserProvided);
+spanless_eq_enum!(UseTreeKind; Simple(0) Nested(0) Glob);
+spanless_eq_enum!(VariantData; Struct(fields recovered) Tuple(0 1) Unit(0));
+spanless_eq_enum!(VisibilityKind; Public Restricted(path id shorthand) Inherited);
+spanless_eq_enum!(WherePredicate; BoundPredicate(0) RegionPredicate(0) EqPredicate(0));
+spanless_eq_enum!(CoroutineKind; Async(span closure_id return_impl_trait_id)
+    Gen(span closure_id return_impl_trait_id)
+    AsyncGen(span closure_id return_impl_trait_id));
+spanless_eq_enum!(ExprKind; Array(0) ConstBlock(0) Call(0 1) MethodCall(0)
+    Tup(0) Binary(0 1 2) Unary(0 1) Lit(0) Cast(0 1) Type(0 1) Let(0 1 2 3)
+    If(0 1 2) While(0 1 2) ForLoop(pat iter body label kind) Loop(0 1 2)
+    Match(0 1) Closure(0) Block(0 1) Gen(0 1 2) Await(0 1) TryBlock(0)
+    Assign(0 1 2) AssignOp(0 1 2) Field(0 1) Index(0 1 2) Underscore
+    Range(0 1 2) Path(0 1) AddrOf(0 1 2) Break(0 1) Continue(0) Ret(0)
+    InlineAsm(0) OffsetOf(0 1) MacCall(0) Struct(0) Repeat(0 1) Paren(0) Try(0)
+    Yield(0) Yeet(0) Become(0) IncludedBytes(0) FormatArgs(0) Err);
+spanless_eq_enum!(InlineAsmOperand; In(reg expr) Out(reg late expr)
+    InOut(reg late expr) SplitInOut(reg late in_expr out_expr) Const(anon_const)
+    Sym(sym));
+spanless_eq_enum!(ItemKind; ExternCrate(0) Use(0) Static(0) Const(0) Fn(0)
+    Mod(0 1) ForeignMod(0) GlobalAsm(0) TyAlias(0) Enum(0 1) Struct(0 1)
+    Union(0 1) Trait(0) TraitAlias(0 1) Impl(0) MacCall(0) MacroDef(0));
+spanless_eq_enum!(LitKind; Str(0 1) ByteStr(0 1) CStr(0 1) Byte(0) Char(0)
+    Int(0 1) Float(0 1) Bool(0) Err);
+spanless_eq_enum!(PatKind; Wild Ident(0 1 2) Struct(0 1 2 3) TupleStruct(0 1 2)
+    Or(0) Path(0 1) Tuple(0) Box(0) Ref(0 1) Lit(0) Range(0 1 2) Slice(0) Rest
+    Never Paren(0) MacCall(0));
+spanless_eq_enum!(TyKind; Slice(0) Array(0 1) Ptr(0) Ref(0 1) BareFn(0) Never
+    Tup(0) AnonStruct(0) AnonUnion(0) Path(0 1) TraitObject(0 1) ImplTrait(0 1)
+    Paren(0) Typeof(0) Infer ImplicitSelf MacCall(0) Err CVarArgs);
+
+impl SpanlessEq for Ident {
+    fn eq(&self, other: &Self) -> bool {
+        self.as_str() == other.as_str()
+    }
+}
+
+impl SpanlessEq for RangeSyntax {
+    fn eq(&self, _other: &Self) -> bool {
+        match self {
+            RangeSyntax::DotDotDot | RangeSyntax::DotDotEq => true,
+        }
+    }
+}
+
+impl SpanlessEq for Param {
+    fn eq(&self, other: &Self) -> bool {
+        let Param {
+            attrs,
+            ty,
+            pat,
+            id,
+            span: _,
+            is_placeholder,
+        } = self;
+        let Param {
+            attrs: attrs2,
+            ty: ty2,
+            pat: pat2,
+            id: id2,
+            span: _,
+            is_placeholder: is_placeholder2,
+        } = other;
+        SpanlessEq::eq(id, id2)
+            && SpanlessEq::eq(is_placeholder, is_placeholder2)
+            && (matches!(ty.kind, TyKind::Err)
+                || matches!(ty2.kind, TyKind::Err)
+                || SpanlessEq::eq(attrs, attrs2)
+                    && SpanlessEq::eq(ty, ty2)
+                    && SpanlessEq::eq(pat, pat2))
+    }
+}
+
+impl SpanlessEq for TokenKind {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (TokenKind::Literal(this), TokenKind::Literal(other)) => SpanlessEq::eq(this, other),
+            (TokenKind::DotDotEq | TokenKind::DotDotDot, _) => match other {
+                TokenKind::DotDotEq | TokenKind::DotDotDot => true,
+                _ => false,
+            },
+            (TokenKind::Interpolated(this), TokenKind::Interpolated(other)) => {
+                let (this, this_span) = this.as_ref();
+                let (other, other_span) = other.as_ref();
+                SpanlessEq::eq(this_span, other_span)
+                    && match (this, other) {
+                        (Nonterminal::NtExpr(this), Nonterminal::NtExpr(other)) => {
+                            SpanlessEq::eq(this, other)
+                        }
+                        _ => this == other,
+                    }
+            }
+            _ => self == other,
+        }
+    }
+}
+
+impl SpanlessEq for TokenStream {
+    fn eq(&self, other: &Self) -> bool {
+        let mut this_trees = self.trees();
+        let mut other_trees = other.trees();
+        loop {
+            let this = match this_trees.next() {
+                None => return other_trees.next().is_none(),
+                Some(tree) => tree,
+            };
+            let other = match other_trees.next() {
+                None => return false,
+                Some(tree) => tree,
+            };
+            if SpanlessEq::eq(this, other) {
+                continue;
+            }
+            if let (TokenTree::Token(this, _), TokenTree::Token(other, _)) = (this, other) {
+                if match (&this.kind, &other.kind) {
+                    (TokenKind::Literal(this), TokenKind::Literal(other)) => {
+                        SpanlessEq::eq(this, other)
+                    }
+                    (TokenKind::DocComment(_kind, style, symbol), TokenKind::Pound) => {
+                        doc_comment(*style, *symbol, &mut other_trees)
+                    }
+                    (TokenKind::Pound, TokenKind::DocComment(_kind, style, symbol)) => {
+                        doc_comment(*style, *symbol, &mut this_trees)
+                    }
+                    _ => false,
+                } {
+                    continue;
+                }
+            }
+            return false;
+        }
+    }
+}
+
+fn doc_comment<'a>(
+    style: AttrStyle,
+    unescaped: Symbol,
+    trees: &mut impl Iterator<Item = &'a TokenTree>,
+) -> bool {
+    if match style {
+        AttrStyle::Outer => false,
+        AttrStyle::Inner => true,
+    } {
+        match trees.next() {
+            Some(TokenTree::Token(
+                Token {
+                    kind: TokenKind::Not,
+                    span: _,
+                },
+                _spacing,
+            )) => {}
+            _ => return false,
+        }
+    }
+    let stream = match trees.next() {
+        Some(TokenTree::Delimited(_span, _spacing, Delimiter::Bracket, stream)) => stream,
+        _ => return false,
+    };
+    let mut trees = stream.trees();
+    match trees.next() {
+        Some(TokenTree::Token(
+            Token {
+                kind: TokenKind::Ident(symbol, false),
+                span: _,
+            },
+            _spacing,
+        )) if *symbol == sym::doc => {}
+        _ => return false,
+    }
+    match trees.next() {
+        Some(TokenTree::Token(
+            Token {
+                kind: TokenKind::Eq,
+                span: _,
+            },
+            _spacing,
+        )) => {}
+        _ => return false,
+    }
+    match trees.next() {
+        Some(TokenTree::Token(token, _spacing)) => {
+            is_escaped_literal_token(token, unescaped) && trees.next().is_none()
+        }
+        _ => false,
+    }
+}
+
+fn is_escaped_literal_token(token: &Token, unescaped: Symbol) -> bool {
+    match token {
+        Token {
+            kind: TokenKind::Literal(lit),
+            span: _,
+        } => match MetaItemLit::from_token_lit(*lit, DUMMY_SP) {
+            Ok(lit) => is_escaped_literal_meta_item_lit(&lit, unescaped),
+            Err(_) => false,
+        },
+        Token {
+            kind: TokenKind::Interpolated(nonterminal),
+            span: _,
+        } => match &nonterminal.0 {
+            Nonterminal::NtExpr(expr) => match &expr.kind {
+                ExprKind::Lit(lit) => is_escaped_lit(lit, unescaped),
+                _ => false,
+            },
+            _ => false,
+        },
+        _ => false,
+    }
+}
+
+fn is_escaped_literal_attr_args(value: &AttrArgsEq, unescaped: Symbol) -> bool {
+    match value {
+        AttrArgsEq::Ast(expr) => match &expr.kind {
+            ExprKind::Lit(lit) => is_escaped_lit(lit, unescaped),
+            _ => false,
+        },
+        AttrArgsEq::Hir(lit) => is_escaped_literal_meta_item_lit(lit, unescaped),
+    }
+}
+
+fn is_escaped_literal_meta_item_lit(lit: &MetaItemLit, unescaped: Symbol) -> bool {
+    match lit {
+        MetaItemLit {
+            symbol: _,
+            suffix: None,
+            kind,
+            span: _,
+        } => is_escaped_lit_kind(kind, unescaped),
+        _ => false,
+    }
+}
+
+fn is_escaped_lit(lit: &Lit, unescaped: Symbol) -> bool {
+    match lit {
+        Lit {
+            kind: token::LitKind::Str,
+            symbol: _,
+            suffix: None,
+        } => match LitKind::from_token_lit(*lit) {
+            Ok(lit_kind) => is_escaped_lit_kind(&lit_kind, unescaped),
+            _ => false,
+        },
+        _ => false,
+    }
+}
+
+fn is_escaped_lit_kind(kind: &LitKind, unescaped: Symbol) -> bool {
+    match kind {
+        LitKind::Str(symbol, StrStyle::Cooked) => {
+            symbol.as_str().replace('\r', "") == unescaped.as_str().replace('\r', "")
+        }
+        _ => false,
+    }
+}
+
+impl SpanlessEq for LazyAttrTokenStream {
+    fn eq(&self, other: &Self) -> bool {
+        let this = self.to_attr_token_stream();
+        let other = other.to_attr_token_stream();
+        SpanlessEq::eq(&this, &other)
+    }
+}
+
+impl SpanlessEq for AttrKind {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (AttrKind::Normal(normal), AttrKind::Normal(normal2)) => {
+                SpanlessEq::eq(normal, normal2)
+            }
+            (AttrKind::DocComment(kind, symbol), AttrKind::DocComment(kind2, symbol2)) => {
+                SpanlessEq::eq(kind, kind2) && SpanlessEq::eq(symbol, symbol2)
+            }
+            (AttrKind::DocComment(kind, unescaped), AttrKind::Normal(normal2)) => {
+                match kind {
+                    CommentKind::Line | CommentKind::Block => {}
+                }
+                let path = Path::from_ident(Ident::with_dummy_span(sym::doc));
+                SpanlessEq::eq(&path, &normal2.item.path)
+                    && match &normal2.item.args {
+                        AttrArgs::Empty | AttrArgs::Delimited(_) => false,
+                        AttrArgs::Eq(_span, value) => {
+                            is_escaped_literal_attr_args(value, *unescaped)
+                        }
+                    }
+            }
+            (AttrKind::Normal(_), AttrKind::DocComment(..)) => SpanlessEq::eq(other, self),
+        }
+    }
+}
+
+impl SpanlessEq for FormatArguments {
+    fn eq(&self, other: &Self) -> bool {
+        SpanlessEq::eq(self.all_args(), other.all_args())
+    }
+}
diff --git a/third_party/rust/syn/tests/common/mod.rs b/third_party/rust/syn/tests/common/mod.rs
new file mode 100644
index 0000000000..2156530b7c
--- /dev/null
+++ b/third_party/rust/syn/tests/common/mod.rs
@@ -0,0 +1,28 @@
+#![allow(dead_code)]
+#![allow(clippy::module_name_repetitions, clippy::shadow_unrelated)]
+
+use rayon::ThreadPoolBuilder;
+use std::env;
+
+pub mod eq;
+pub mod parse;
+
+/// Read the `ABORT_AFTER_FAILURE` environment variable, and parse it.
+pub fn abort_after() -> usize {
+    match env::var("ABORT_AFTER_FAILURE") {
+        Ok(s) => s.parse().expect("failed to parse ABORT_AFTER_FAILURE"),
+        Err(_) => usize::max_value(),
+    }
+}
+
+/// Configure Rayon threadpool.
+pub fn rayon_init() {
+    let stack_size = match env::var("RUST_MIN_STACK") {
+        Ok(s) => s.parse().expect("failed to parse RUST_MIN_STACK"),
+        Err(_) => 20 * 1024 * 1024,
+    };
+    ThreadPoolBuilder::new()
+        .stack_size(stack_size)
+        .build_global()
+        .unwrap();
+}
diff --git a/third_party/rust/syn/tests/common/parse.rs b/third_party/rust/syn/tests/common/parse.rs
new file mode 100644
index 0000000000..73be101860
--- /dev/null
+++ b/third_party/rust/syn/tests/common/parse.rs
@@ -0,0 +1,51 @@
+extern crate rustc_ast;
+extern crate rustc_driver;
+extern crate rustc_expand;
+extern crate rustc_parse as parse;
+extern crate rustc_session;
+extern crate rustc_span;
+
+use rustc_ast::ast;
+use rustc_ast::ptr::P;
+use rustc_session::parse::ParseSess;
+use rustc_span::source_map::FilePathMapping;
+use rustc_span::FileName;
+use std::panic;
+
+pub fn librustc_expr(input: &str) -> Option<P<ast::Expr>> {
+    match panic::catch_unwind(|| {
+        let locale_resources = rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec();
+        let file_path_mapping = FilePathMapping::empty();
+        let sess = ParseSess::new(locale_resources, file_path_mapping);
+        let e = parse::new_parser_from_source_str(
+            &sess,
+            FileName::Custom("test_precedence".to_string()),
+            input.to_string(),
+        )
+        .parse_expr();
+        match e {
+            Ok(expr) => Some(expr),
+            Err(mut diagnostic) => {
+                diagnostic.emit();
+                None
+            }
+        }
+    }) {
+        Ok(Some(e)) => Some(e),
+        Ok(None) => None,
+        Err(_) => {
+            errorf!("librustc panicked\n");
+            None
+        }
+    }
+}
+
+pub fn syn_expr(input: &str) -> Option<syn::Expr> {
+    match syn::parse_str(input) {
+        Ok(e) => Some(e),
+        Err(msg) => {
+            errorf!("syn failed to parse\n{:?}\n", msg);
+            None
+        }
+    }
+}
diff --git a/third_party/rust/syn/tests/debug/gen.rs b/third_party/rust/syn/tests/debug/gen.rs
new file mode 100644
index 0000000000..1548d8b6ba
--- /dev/null
+++ b/third_party/rust/syn/tests/debug/gen.rs
@@ -0,0 +1,5157 @@
+// This file is @generated by syn-internal-codegen.
+// It is not intended for manual editing.
+
+#![allow(repr_transparent_external_private_fields)]
+#![allow(clippy::match_wildcard_for_single_variants)]
+use super::{Lite, Present};
+use ref_cast::RefCast;
+use std::fmt::{self, Debug, Display};
+impl Debug for Lite<syn::Abi> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Abi");
+        if let Some(val) = &self.value.name {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::LitStr);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("name", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::AngleBracketedGenericArguments> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("AngleBracketedGenericArguments");
+        if self.value.colon2_token.is_some() {
+            formatter.field("colon2_token", &Present);
+        }
+        if !self.value.args.is_empty() {
+            formatter.field("args", Lite(&self.value.args));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Arm> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Arm");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("pat", Lite(&self.value.pat));
+        if let Some(val) = &self.value.guard {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::If, Box<syn::Expr>));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("guard", Print::ref_cast(val));
+        }
+        formatter.field("body", Lite(&self.value.body));
+        if self.value.comma.is_some() {
+            formatter.field("comma", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::AssocConst> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("AssocConst");
+        formatter.field("ident", Lite(&self.value.ident));
+        if let Some(val) = &self.value.generics {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::AngleBracketedGenericArguments);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("generics", Print::ref_cast(val));
+        }
+        formatter.field("value", Lite(&self.value.value));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::AssocType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("AssocType");
+        formatter.field("ident", Lite(&self.value.ident));
+        if let Some(val) = &self.value.generics {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::AngleBracketedGenericArguments);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("generics", Print::ref_cast(val));
+        }
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::AttrStyle> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::AttrStyle::Outer => formatter.write_str("AttrStyle::Outer"),
+            syn::AttrStyle::Inner(_val) => {
+                formatter.write_str("AttrStyle::Inner")?;
+                Ok(())
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::Attribute> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Attribute");
+        formatter.field("style", Lite(&self.value.style));
+        formatter.field("meta", Lite(&self.value.meta));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::BareFnArg> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("BareFnArg");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.name {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((proc_macro2::Ident, syn::token::Colon));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("name", Print::ref_cast(val));
+        }
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::BareVariadic> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("BareVariadic");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.name {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((proc_macro2::Ident, syn::token::Colon));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("name", Print::ref_cast(val));
+        }
+        if self.value.comma.is_some() {
+            formatter.field("comma", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::BinOp> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::BinOp::Add(_val) => {
+                formatter.write_str("BinOp::Add")?;
+                Ok(())
+            }
+            syn::BinOp::Sub(_val) => {
+                formatter.write_str("BinOp::Sub")?;
+                Ok(())
+            }
+            syn::BinOp::Mul(_val) => {
+                formatter.write_str("BinOp::Mul")?;
+                Ok(())
+            }
+            syn::BinOp::Div(_val) => {
+                formatter.write_str("BinOp::Div")?;
+                Ok(())
+            }
+            syn::BinOp::Rem(_val) => {
+                formatter.write_str("BinOp::Rem")?;
+                Ok(())
+            }
+            syn::BinOp::And(_val) => {
+                formatter.write_str("BinOp::And")?;
+                Ok(())
+            }
+            syn::BinOp::Or(_val) => {
+                formatter.write_str("BinOp::Or")?;
+                Ok(())
+            }
+            syn::BinOp::BitXor(_val) => {
+                formatter.write_str("BinOp::BitXor")?;
+                Ok(())
+            }
+            syn::BinOp::BitAnd(_val) => {
+                formatter.write_str("BinOp::BitAnd")?;
+                Ok(())
+            }
+            syn::BinOp::BitOr(_val) => {
+                formatter.write_str("BinOp::BitOr")?;
+                Ok(())
+            }
+            syn::BinOp::Shl(_val) => {
+                formatter.write_str("BinOp::Shl")?;
+                Ok(())
+            }
+            syn::BinOp::Shr(_val) => {
+                formatter.write_str("BinOp::Shr")?;
+                Ok(())
+            }
+            syn::BinOp::Eq(_val) => {
+                formatter.write_str("BinOp::Eq")?;
+                Ok(())
+            }
+            syn::BinOp::Lt(_val) => {
+                formatter.write_str("BinOp::Lt")?;
+                Ok(())
+            }
+            syn::BinOp::Le(_val) => {
+                formatter.write_str("BinOp::Le")?;
+                Ok(())
+            }
+            syn::BinOp::Ne(_val) => {
+                formatter.write_str("BinOp::Ne")?;
+                Ok(())
+            }
+            syn::BinOp::Ge(_val) => {
+                formatter.write_str("BinOp::Ge")?;
+                Ok(())
+            }
+            syn::BinOp::Gt(_val) => {
+                formatter.write_str("BinOp::Gt")?;
+                Ok(())
+            }
+            syn::BinOp::AddAssign(_val) => {
+                formatter.write_str("BinOp::AddAssign")?;
+                Ok(())
+            }
+            syn::BinOp::SubAssign(_val) => {
+                formatter.write_str("BinOp::SubAssign")?;
+                Ok(())
+            }
+            syn::BinOp::MulAssign(_val) => {
+                formatter.write_str("BinOp::MulAssign")?;
+                Ok(())
+            }
+            syn::BinOp::DivAssign(_val) => {
+                formatter.write_str("BinOp::DivAssign")?;
+                Ok(())
+            }
+            syn::BinOp::RemAssign(_val) => {
+                formatter.write_str("BinOp::RemAssign")?;
+                Ok(())
+            }
+            syn::BinOp::BitXorAssign(_val) => {
+                formatter.write_str("BinOp::BitXorAssign")?;
+                Ok(())
+            }
+            syn::BinOp::BitAndAssign(_val) => {
+                formatter.write_str("BinOp::BitAndAssign")?;
+                Ok(())
+            }
+            syn::BinOp::BitOrAssign(_val) => {
+                formatter.write_str("BinOp::BitOrAssign")?;
+                Ok(())
+            }
+            syn::BinOp::ShlAssign(_val) => {
+                formatter.write_str("BinOp::ShlAssign")?;
+                Ok(())
+            }
+            syn::BinOp::ShrAssign(_val) => {
+                formatter.write_str("BinOp::ShrAssign")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::Block> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Block");
+        formatter.field("stmts", Lite(&self.value.stmts));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::BoundLifetimes> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("BoundLifetimes");
+        if !self.value.lifetimes.is_empty() {
+            formatter.field("lifetimes", Lite(&self.value.lifetimes));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ConstParam> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ConstParam");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("ty", Lite(&self.value.ty));
+        if self.value.eq_token.is_some() {
+            formatter.field("eq_token", &Present);
+        }
+        if let Some(val) = &self.value.default {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Expr);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("default", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Constraint> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Constraint");
+        formatter.field("ident", Lite(&self.value.ident));
+        if let Some(val) = &self.value.generics {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::AngleBracketedGenericArguments);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("generics", Print::ref_cast(val));
+        }
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Data> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Data::Struct(_val) => {
+                let mut formatter = formatter.debug_struct("Data::Struct");
+                formatter.field("fields", Lite(&_val.fields));
+                if _val.semi_token.is_some() {
+                    formatter.field("semi_token", &Present);
+                }
+                formatter.finish()
+            }
+            syn::Data::Enum(_val) => {
+                let mut formatter = formatter.debug_struct("Data::Enum");
+                if !_val.variants.is_empty() {
+                    formatter.field("variants", Lite(&_val.variants));
+                }
+                formatter.finish()
+            }
+            syn::Data::Union(_val) => {
+                let mut formatter = formatter.debug_struct("Data::Union");
+                formatter.field("fields", Lite(&_val.fields));
+                formatter.finish()
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::DataEnum> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("DataEnum");
+        if !self.value.variants.is_empty() {
+            formatter.field("variants", Lite(&self.value.variants));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::DataStruct> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("DataStruct");
+        formatter.field("fields", Lite(&self.value.fields));
+        if self.value.semi_token.is_some() {
+            formatter.field("semi_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::DataUnion> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("DataUnion");
+        formatter.field("fields", Lite(&self.value.fields));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::DeriveInput> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("DeriveInput");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.field("data", Lite(&self.value.data));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Expr> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Expr::Array(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Array");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if !_val.elems.is_empty() {
+                    formatter.field("elems", Lite(&_val.elems));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Assign(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Assign");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("left", Lite(&_val.left));
+                formatter.field("right", Lite(&_val.right));
+                formatter.finish()
+            }
+            syn::Expr::Async(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Async");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if _val.capture.is_some() {
+                    formatter.field("capture", &Present);
+                }
+                formatter.field("block", Lite(&_val.block));
+                formatter.finish()
+            }
+            syn::Expr::Await(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Await");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("base", Lite(&_val.base));
+                formatter.finish()
+            }
+            syn::Expr::Binary(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Binary");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("left", Lite(&_val.left));
+                formatter.field("op", Lite(&_val.op));
+                formatter.field("right", Lite(&_val.right));
+                formatter.finish()
+            }
+            syn::Expr::Block(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Block");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.label {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Label);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("label", Print::ref_cast(val));
+                }
+                formatter.field("block", Lite(&_val.block));
+                formatter.finish()
+            }
+            syn::Expr::Break(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Break");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.label {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Lifetime);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("label", Print::ref_cast(val));
+                }
+                if let Some(val) = &_val.expr {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(Box<syn::Expr>);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("expr", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Call(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Call");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("func", Lite(&_val.func));
+                if !_val.args.is_empty() {
+                    formatter.field("args", Lite(&_val.args));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Cast(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Cast");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.field("ty", Lite(&_val.ty));
+                formatter.finish()
+            }
+            syn::Expr::Closure(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Closure");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.lifetimes {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::BoundLifetimes);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("lifetimes", Print::ref_cast(val));
+                }
+                if _val.constness.is_some() {
+                    formatter.field("constness", &Present);
+                }
+                if _val.movability.is_some() {
+                    formatter.field("movability", &Present);
+                }
+                if _val.asyncness.is_some() {
+                    formatter.field("asyncness", &Present);
+                }
+                if _val.capture.is_some() {
+                    formatter.field("capture", &Present);
+                }
+                if !_val.inputs.is_empty() {
+                    formatter.field("inputs", Lite(&_val.inputs));
+                }
+                formatter.field("output", Lite(&_val.output));
+                formatter.field("body", Lite(&_val.body));
+                formatter.finish()
+            }
+            syn::Expr::Const(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Const");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("block", Lite(&_val.block));
+                formatter.finish()
+            }
+            syn::Expr::Continue(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Continue");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.label {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Lifetime);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("label", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Field(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Field");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("base", Lite(&_val.base));
+                formatter.field("member", Lite(&_val.member));
+                formatter.finish()
+            }
+            syn::Expr::ForLoop(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::ForLoop");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.label {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Label);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("label", Print::ref_cast(val));
+                }
+                formatter.field("pat", Lite(&_val.pat));
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.field("body", Lite(&_val.body));
+                formatter.finish()
+            }
+            syn::Expr::Group(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Group");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::Expr::If(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::If");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("cond", Lite(&_val.cond));
+                formatter.field("then_branch", Lite(&_val.then_branch));
+                if let Some(val) = &_val.else_branch {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print((syn::token::Else, Box<syn::Expr>));
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0.1), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("else_branch", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Index(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Index");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.field("index", Lite(&_val.index));
+                formatter.finish()
+            }
+            syn::Expr::Infer(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Infer");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Let(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Let");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("pat", Lite(&_val.pat));
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::Expr::Lit(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Lit");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("lit", Lite(&_val.lit));
+                formatter.finish()
+            }
+            syn::Expr::Loop(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Loop");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.label {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Label);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("label", Print::ref_cast(val));
+                }
+                formatter.field("body", Lite(&_val.body));
+                formatter.finish()
+            }
+            syn::Expr::Macro(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Macro");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("mac", Lite(&_val.mac));
+                formatter.finish()
+            }
+            syn::Expr::Match(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Match");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("expr", Lite(&_val.expr));
+                if !_val.arms.is_empty() {
+                    formatter.field("arms", Lite(&_val.arms));
+                }
+                formatter.finish()
+            }
+            syn::Expr::MethodCall(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::MethodCall");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("receiver", Lite(&_val.receiver));
+                formatter.field("method", Lite(&_val.method));
+                if let Some(val) = &_val.turbofish {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::AngleBracketedGenericArguments);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("turbofish", Print::ref_cast(val));
+                }
+                if !_val.args.is_empty() {
+                    formatter.field("args", Lite(&_val.args));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Paren(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Paren");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::Expr::Path(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Path");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.qself {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::QSelf);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("qself", Print::ref_cast(val));
+                }
+                formatter.field("path", Lite(&_val.path));
+                formatter.finish()
+            }
+            syn::Expr::Range(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Range");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.start {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(Box<syn::Expr>);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("start", Print::ref_cast(val));
+                }
+                formatter.field("limits", Lite(&_val.limits));
+                if let Some(val) = &_val.end {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(Box<syn::Expr>);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("end", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Reference(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Reference");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if _val.mutability.is_some() {
+                    formatter.field("mutability", &Present);
+                }
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::Expr::Repeat(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Repeat");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.field("len", Lite(&_val.len));
+                formatter.finish()
+            }
+            syn::Expr::Return(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Return");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.expr {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(Box<syn::Expr>);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("expr", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Struct(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Struct");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.qself {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::QSelf);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("qself", Print::ref_cast(val));
+                }
+                formatter.field("path", Lite(&_val.path));
+                if !_val.fields.is_empty() {
+                    formatter.field("fields", Lite(&_val.fields));
+                }
+                if _val.dot2_token.is_some() {
+                    formatter.field("dot2_token", &Present);
+                }
+                if let Some(val) = &_val.rest {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(Box<syn::Expr>);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("rest", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Try(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Try");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::Expr::TryBlock(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::TryBlock");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("block", Lite(&_val.block));
+                formatter.finish()
+            }
+            syn::Expr::Tuple(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Tuple");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if !_val.elems.is_empty() {
+                    formatter.field("elems", Lite(&_val.elems));
+                }
+                formatter.finish()
+            }
+            syn::Expr::Unary(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Unary");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("op", Lite(&_val.op));
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::Expr::Unsafe(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Unsafe");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("block", Lite(&_val.block));
+                formatter.finish()
+            }
+            syn::Expr::Verbatim(_val) => {
+                formatter.write_str("Expr::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            syn::Expr::While(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::While");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.label {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Label);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("label", Print::ref_cast(val));
+                }
+                formatter.field("cond", Lite(&_val.cond));
+                formatter.field("body", Lite(&_val.body));
+                formatter.finish()
+            }
+            syn::Expr::Yield(_val) => {
+                let mut formatter = formatter.debug_struct("Expr::Yield");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.expr {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(Box<syn::Expr>);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("expr", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::ExprArray> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprArray");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if !self.value.elems.is_empty() {
+            formatter.field("elems", Lite(&self.value.elems));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprAssign> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprAssign");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("left", Lite(&self.value.left));
+        formatter.field("right", Lite(&self.value.right));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprAsync> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprAsync");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if self.value.capture.is_some() {
+            formatter.field("capture", &Present);
+        }
+        formatter.field("block", Lite(&self.value.block));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprAwait> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprAwait");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("base", Lite(&self.value.base));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprBinary> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprBinary");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("left", Lite(&self.value.left));
+        formatter.field("op", Lite(&self.value.op));
+        formatter.field("right", Lite(&self.value.right));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprBlock> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprBlock");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.label {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Label);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("label", Print::ref_cast(val));
+        }
+        formatter.field("block", Lite(&self.value.block));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprBreak> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprBreak");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.label {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Lifetime);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("label", Print::ref_cast(val));
+        }
+        if let Some(val) = &self.value.expr {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(Box<syn::Expr>);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("expr", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprCall> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprCall");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("func", Lite(&self.value.func));
+        if !self.value.args.is_empty() {
+            formatter.field("args", Lite(&self.value.args));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprCast> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprCast");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprClosure> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprClosure");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.lifetimes {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::BoundLifetimes);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("lifetimes", Print::ref_cast(val));
+        }
+        if self.value.constness.is_some() {
+            formatter.field("constness", &Present);
+        }
+        if self.value.movability.is_some() {
+            formatter.field("movability", &Present);
+        }
+        if self.value.asyncness.is_some() {
+            formatter.field("asyncness", &Present);
+        }
+        if self.value.capture.is_some() {
+            formatter.field("capture", &Present);
+        }
+        if !self.value.inputs.is_empty() {
+            formatter.field("inputs", Lite(&self.value.inputs));
+        }
+        formatter.field("output", Lite(&self.value.output));
+        formatter.field("body", Lite(&self.value.body));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprConst> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprConst");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("block", Lite(&self.value.block));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprContinue> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprContinue");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.label {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Lifetime);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("label", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprField> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprField");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("base", Lite(&self.value.base));
+        formatter.field("member", Lite(&self.value.member));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprForLoop> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprForLoop");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.label {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Label);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("label", Print::ref_cast(val));
+        }
+        formatter.field("pat", Lite(&self.value.pat));
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.field("body", Lite(&self.value.body));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprGroup> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprGroup");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprIf> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprIf");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("cond", Lite(&self.value.cond));
+        formatter.field("then_branch", Lite(&self.value.then_branch));
+        if let Some(val) = &self.value.else_branch {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::Else, Box<syn::Expr>));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("else_branch", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprIndex> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprIndex");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.field("index", Lite(&self.value.index));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprInfer> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprInfer");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprLet> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprLet");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("pat", Lite(&self.value.pat));
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprLit> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprLit");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("lit", Lite(&self.value.lit));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprLoop> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprLoop");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.label {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Label);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("label", Print::ref_cast(val));
+        }
+        formatter.field("body", Lite(&self.value.body));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprMacro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprMacro");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("mac", Lite(&self.value.mac));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprMatch> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprMatch");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        if !self.value.arms.is_empty() {
+            formatter.field("arms", Lite(&self.value.arms));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprMethodCall> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprMethodCall");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("receiver", Lite(&self.value.receiver));
+        formatter.field("method", Lite(&self.value.method));
+        if let Some(val) = &self.value.turbofish {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::AngleBracketedGenericArguments);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("turbofish", Print::ref_cast(val));
+        }
+        if !self.value.args.is_empty() {
+            formatter.field("args", Lite(&self.value.args));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprParen> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprParen");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprPath> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprPath");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.qself {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::QSelf);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("qself", Print::ref_cast(val));
+        }
+        formatter.field("path", Lite(&self.value.path));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprRange> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprRange");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.start {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(Box<syn::Expr>);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("start", Print::ref_cast(val));
+        }
+        formatter.field("limits", Lite(&self.value.limits));
+        if let Some(val) = &self.value.end {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(Box<syn::Expr>);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("end", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprReference> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprReference");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if self.value.mutability.is_some() {
+            formatter.field("mutability", &Present);
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprRepeat> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprRepeat");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.field("len", Lite(&self.value.len));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprReturn> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprReturn");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.expr {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(Box<syn::Expr>);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("expr", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprStruct> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprStruct");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.qself {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::QSelf);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("qself", Print::ref_cast(val));
+        }
+        formatter.field("path", Lite(&self.value.path));
+        if !self.value.fields.is_empty() {
+            formatter.field("fields", Lite(&self.value.fields));
+        }
+        if self.value.dot2_token.is_some() {
+            formatter.field("dot2_token", &Present);
+        }
+        if let Some(val) = &self.value.rest {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(Box<syn::Expr>);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("rest", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprTry> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprTry");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprTryBlock> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprTryBlock");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("block", Lite(&self.value.block));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprTuple> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprTuple");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if !self.value.elems.is_empty() {
+            formatter.field("elems", Lite(&self.value.elems));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprUnary> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprUnary");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("op", Lite(&self.value.op));
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprUnsafe> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprUnsafe");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("block", Lite(&self.value.block));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprWhile> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprWhile");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.label {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Label);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("label", Print::ref_cast(val));
+        }
+        formatter.field("cond", Lite(&self.value.cond));
+        formatter.field("body", Lite(&self.value.body));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ExprYield> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ExprYield");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.expr {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(Box<syn::Expr>);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("expr", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Field> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Field");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        match self.value.mutability {
+            syn::FieldMutability::None => {}
+            _ => {
+                formatter.field("mutability", Lite(&self.value.mutability));
+            }
+        }
+        if let Some(val) = &self.value.ident {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(proc_macro2::Ident);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("ident", Print::ref_cast(val));
+        }
+        if self.value.colon_token.is_some() {
+            formatter.field("colon_token", &Present);
+        }
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::FieldMutability> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::FieldMutability::None => formatter.write_str("FieldMutability::None"),
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::FieldPat> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("FieldPat");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("member", Lite(&self.value.member));
+        if self.value.colon_token.is_some() {
+            formatter.field("colon_token", &Present);
+        }
+        formatter.field("pat", Lite(&self.value.pat));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::FieldValue> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("FieldValue");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("member", Lite(&self.value.member));
+        if self.value.colon_token.is_some() {
+            formatter.field("colon_token", &Present);
+        }
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Fields> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Fields::Named(_val) => {
+                let mut formatter = formatter.debug_struct("Fields::Named");
+                if !_val.named.is_empty() {
+                    formatter.field("named", Lite(&_val.named));
+                }
+                formatter.finish()
+            }
+            syn::Fields::Unnamed(_val) => {
+                let mut formatter = formatter.debug_struct("Fields::Unnamed");
+                if !_val.unnamed.is_empty() {
+                    formatter.field("unnamed", Lite(&_val.unnamed));
+                }
+                formatter.finish()
+            }
+            syn::Fields::Unit => formatter.write_str("Fields::Unit"),
+        }
+    }
+}
+impl Debug for Lite<syn::FieldsNamed> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("FieldsNamed");
+        if !self.value.named.is_empty() {
+            formatter.field("named", Lite(&self.value.named));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::FieldsUnnamed> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("FieldsUnnamed");
+        if !self.value.unnamed.is_empty() {
+            formatter.field("unnamed", Lite(&self.value.unnamed));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::File> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("File");
+        if let Some(val) = &self.value.shebang {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(String);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("shebang", Print::ref_cast(val));
+        }
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if !self.value.items.is_empty() {
+            formatter.field("items", Lite(&self.value.items));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::FnArg> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::FnArg::Receiver(_val) => {
+                formatter.write_str("FnArg::Receiver")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::FnArg::Typed(_val) => {
+                formatter.write_str("FnArg::Typed")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::ForeignItem> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::ForeignItem::Fn(_val) => {
+                let mut formatter = formatter.debug_struct("ForeignItem::Fn");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("sig", Lite(&_val.sig));
+                formatter.finish()
+            }
+            syn::ForeignItem::Static(_val) => {
+                let mut formatter = formatter.debug_struct("ForeignItem::Static");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                match _val.mutability {
+                    syn::StaticMutability::None => {}
+                    _ => {
+                        formatter.field("mutability", Lite(&_val.mutability));
+                    }
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("ty", Lite(&_val.ty));
+                formatter.finish()
+            }
+            syn::ForeignItem::Type(_val) => {
+                let mut formatter = formatter.debug_struct("ForeignItem::Type");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                formatter.finish()
+            }
+            syn::ForeignItem::Macro(_val) => {
+                let mut formatter = formatter.debug_struct("ForeignItem::Macro");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("mac", Lite(&_val.mac));
+                if _val.semi_token.is_some() {
+                    formatter.field("semi_token", &Present);
+                }
+                formatter.finish()
+            }
+            syn::ForeignItem::Verbatim(_val) => {
+                formatter.write_str("ForeignItem::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::ForeignItemFn> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ForeignItemFn");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("sig", Lite(&self.value.sig));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ForeignItemMacro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ForeignItemMacro");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("mac", Lite(&self.value.mac));
+        if self.value.semi_token.is_some() {
+            formatter.field("semi_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ForeignItemStatic> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ForeignItemStatic");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        match self.value.mutability {
+            syn::StaticMutability::None => {}
+            _ => {
+                formatter.field("mutability", Lite(&self.value.mutability));
+            }
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ForeignItemType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ForeignItemType");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::GenericArgument> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::GenericArgument::Lifetime(_val) => {
+                formatter.write_str("GenericArgument::Lifetime")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::GenericArgument::Type(_val) => {
+                formatter.write_str("GenericArgument::Type")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::GenericArgument::Const(_val) => {
+                formatter.write_str("GenericArgument::Const")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::GenericArgument::AssocType(_val) => {
+                formatter.write_str("GenericArgument::AssocType")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::GenericArgument::AssocConst(_val) => {
+                formatter.write_str("GenericArgument::AssocConst")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::GenericArgument::Constraint(_val) => {
+                formatter.write_str("GenericArgument::Constraint")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::GenericParam> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::GenericParam::Lifetime(_val) => {
+                formatter.write_str("GenericParam::Lifetime")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::GenericParam::Type(_val) => {
+                formatter.write_str("GenericParam::Type")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::GenericParam::Const(_val) => {
+                formatter.write_str("GenericParam::Const")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::Generics> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Generics");
+        if self.value.lt_token.is_some() {
+            formatter.field("lt_token", &Present);
+        }
+        if !self.value.params.is_empty() {
+            formatter.field("params", Lite(&self.value.params));
+        }
+        if self.value.gt_token.is_some() {
+            formatter.field("gt_token", &Present);
+        }
+        if let Some(val) = &self.value.where_clause {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::WhereClause);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("where_clause", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ImplItem> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::ImplItem::Const(_val) => {
+                let mut formatter = formatter.debug_struct("ImplItem::Const");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                if _val.defaultness.is_some() {
+                    formatter.field("defaultness", &Present);
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                formatter.field("ty", Lite(&_val.ty));
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::ImplItem::Fn(_val) => {
+                let mut formatter = formatter.debug_struct("ImplItem::Fn");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                if _val.defaultness.is_some() {
+                    formatter.field("defaultness", &Present);
+                }
+                formatter.field("sig", Lite(&_val.sig));
+                formatter.field("block", Lite(&_val.block));
+                formatter.finish()
+            }
+            syn::ImplItem::Type(_val) => {
+                let mut formatter = formatter.debug_struct("ImplItem::Type");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                if _val.defaultness.is_some() {
+                    formatter.field("defaultness", &Present);
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                formatter.field("ty", Lite(&_val.ty));
+                formatter.finish()
+            }
+            syn::ImplItem::Macro(_val) => {
+                let mut formatter = formatter.debug_struct("ImplItem::Macro");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("mac", Lite(&_val.mac));
+                if _val.semi_token.is_some() {
+                    formatter.field("semi_token", &Present);
+                }
+                formatter.finish()
+            }
+            syn::ImplItem::Verbatim(_val) => {
+                formatter.write_str("ImplItem::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::ImplItemConst> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ImplItemConst");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        if self.value.defaultness.is_some() {
+            formatter.field("defaultness", &Present);
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ImplItemFn> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ImplItemFn");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        if self.value.defaultness.is_some() {
+            formatter.field("defaultness", &Present);
+        }
+        formatter.field("sig", Lite(&self.value.sig));
+        formatter.field("block", Lite(&self.value.block));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ImplItemMacro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ImplItemMacro");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("mac", Lite(&self.value.mac));
+        if self.value.semi_token.is_some() {
+            formatter.field("semi_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ImplItemType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ImplItemType");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        if self.value.defaultness.is_some() {
+            formatter.field("defaultness", &Present);
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ImplRestriction> {
+    fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+        unreachable!()
+    }
+}
+impl Debug for Lite<syn::Index> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Index");
+        formatter.field("index", Lite(&self.value.index));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Item> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Item::Const(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Const");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                formatter.field("ty", Lite(&_val.ty));
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::Item::Enum(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Enum");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                if !_val.variants.is_empty() {
+                    formatter.field("variants", Lite(&_val.variants));
+                }
+                formatter.finish()
+            }
+            syn::Item::ExternCrate(_val) => {
+                let mut formatter = formatter.debug_struct("Item::ExternCrate");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("ident", Lite(&_val.ident));
+                if let Some(val) = &_val.rename {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print((syn::token::As, proc_macro2::Ident));
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0.1), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("rename", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Item::Fn(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Fn");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("sig", Lite(&_val.sig));
+                formatter.field("block", Lite(&_val.block));
+                formatter.finish()
+            }
+            syn::Item::ForeignMod(_val) => {
+                let mut formatter = formatter.debug_struct("Item::ForeignMod");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if _val.unsafety.is_some() {
+                    formatter.field("unsafety", &Present);
+                }
+                formatter.field("abi", Lite(&_val.abi));
+                if !_val.items.is_empty() {
+                    formatter.field("items", Lite(&_val.items));
+                }
+                formatter.finish()
+            }
+            syn::Item::Impl(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Impl");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if _val.defaultness.is_some() {
+                    formatter.field("defaultness", &Present);
+                }
+                if _val.unsafety.is_some() {
+                    formatter.field("unsafety", &Present);
+                }
+                formatter.field("generics", Lite(&_val.generics));
+                if let Some(val) = &_val.trait_ {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print((Option<syn::token::Not>, syn::Path, syn::token::For));
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(
+                                &(
+                                    &super::Option {
+                                        present: self.0.0.is_some(),
+                                    },
+                                    Lite(&self.0.1),
+                                ),
+                                formatter,
+                            )?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("trait_", Print::ref_cast(val));
+                }
+                formatter.field("self_ty", Lite(&_val.self_ty));
+                if !_val.items.is_empty() {
+                    formatter.field("items", Lite(&_val.items));
+                }
+                formatter.finish()
+            }
+            syn::Item::Macro(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Macro");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.ident {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(proc_macro2::Ident);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("ident", Print::ref_cast(val));
+                }
+                formatter.field("mac", Lite(&_val.mac));
+                if _val.semi_token.is_some() {
+                    formatter.field("semi_token", &Present);
+                }
+                formatter.finish()
+            }
+            syn::Item::Mod(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Mod");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                if _val.unsafety.is_some() {
+                    formatter.field("unsafety", &Present);
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                if let Some(val) = &_val.content {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print((syn::token::Brace, Vec<syn::Item>));
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0.1), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("content", Print::ref_cast(val));
+                }
+                if _val.semi.is_some() {
+                    formatter.field("semi", &Present);
+                }
+                formatter.finish()
+            }
+            syn::Item::Static(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Static");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                match _val.mutability {
+                    syn::StaticMutability::None => {}
+                    _ => {
+                        formatter.field("mutability", Lite(&_val.mutability));
+                    }
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("ty", Lite(&_val.ty));
+                formatter.field("expr", Lite(&_val.expr));
+                formatter.finish()
+            }
+            syn::Item::Struct(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Struct");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                formatter.field("fields", Lite(&_val.fields));
+                if _val.semi_token.is_some() {
+                    formatter.field("semi_token", &Present);
+                }
+                formatter.finish()
+            }
+            syn::Item::Trait(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Trait");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                if _val.unsafety.is_some() {
+                    formatter.field("unsafety", &Present);
+                }
+                if _val.auto_token.is_some() {
+                    formatter.field("auto_token", &Present);
+                }
+                if let Some(val) = &_val.restriction {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::ImplRestriction);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("restriction", Print::ref_cast(val));
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                if _val.colon_token.is_some() {
+                    formatter.field("colon_token", &Present);
+                }
+                if !_val.supertraits.is_empty() {
+                    formatter.field("supertraits", Lite(&_val.supertraits));
+                }
+                if !_val.items.is_empty() {
+                    formatter.field("items", Lite(&_val.items));
+                }
+                formatter.finish()
+            }
+            syn::Item::TraitAlias(_val) => {
+                let mut formatter = formatter.debug_struct("Item::TraitAlias");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                if !_val.bounds.is_empty() {
+                    formatter.field("bounds", Lite(&_val.bounds));
+                }
+                formatter.finish()
+            }
+            syn::Item::Type(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Type");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                formatter.field("ty", Lite(&_val.ty));
+                formatter.finish()
+            }
+            syn::Item::Union(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Union");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                formatter.field("fields", Lite(&_val.fields));
+                formatter.finish()
+            }
+            syn::Item::Use(_val) => {
+                let mut formatter = formatter.debug_struct("Item::Use");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("vis", Lite(&_val.vis));
+                if _val.leading_colon.is_some() {
+                    formatter.field("leading_colon", &Present);
+                }
+                formatter.field("tree", Lite(&_val.tree));
+                formatter.finish()
+            }
+            syn::Item::Verbatim(_val) => {
+                formatter.write_str("Item::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::ItemConst> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemConst");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemEnum> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemEnum");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        if !self.value.variants.is_empty() {
+            formatter.field("variants", Lite(&self.value.variants));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemExternCrate> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemExternCrate");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        if let Some(val) = &self.value.rename {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::As, proc_macro2::Ident));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("rename", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemFn> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemFn");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("sig", Lite(&self.value.sig));
+        formatter.field("block", Lite(&self.value.block));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemForeignMod> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemForeignMod");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if self.value.unsafety.is_some() {
+            formatter.field("unsafety", &Present);
+        }
+        formatter.field("abi", Lite(&self.value.abi));
+        if !self.value.items.is_empty() {
+            formatter.field("items", Lite(&self.value.items));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemImpl> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemImpl");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if self.value.defaultness.is_some() {
+            formatter.field("defaultness", &Present);
+        }
+        if self.value.unsafety.is_some() {
+            formatter.field("unsafety", &Present);
+        }
+        formatter.field("generics", Lite(&self.value.generics));
+        if let Some(val) = &self.value.trait_ {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((Option<syn::token::Not>, syn::Path, syn::token::For));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(
+                        &(
+                            &super::Option {
+                                present: self.0.0.is_some(),
+                            },
+                            Lite(&self.0.1),
+                        ),
+                        formatter,
+                    )?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("trait_", Print::ref_cast(val));
+        }
+        formatter.field("self_ty", Lite(&self.value.self_ty));
+        if !self.value.items.is_empty() {
+            formatter.field("items", Lite(&self.value.items));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemMacro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemMacro");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.ident {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(proc_macro2::Ident);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("ident", Print::ref_cast(val));
+        }
+        formatter.field("mac", Lite(&self.value.mac));
+        if self.value.semi_token.is_some() {
+            formatter.field("semi_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemMod> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemMod");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        if self.value.unsafety.is_some() {
+            formatter.field("unsafety", &Present);
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        if let Some(val) = &self.value.content {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::Brace, Vec<syn::Item>));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("content", Print::ref_cast(val));
+        }
+        if self.value.semi.is_some() {
+            formatter.field("semi", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemStatic> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemStatic");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        match self.value.mutability {
+            syn::StaticMutability::None => {}
+            _ => {
+                formatter.field("mutability", Lite(&self.value.mutability));
+            }
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.field("expr", Lite(&self.value.expr));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemStruct> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemStruct");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.field("fields", Lite(&self.value.fields));
+        if self.value.semi_token.is_some() {
+            formatter.field("semi_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemTrait> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemTrait");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        if self.value.unsafety.is_some() {
+            formatter.field("unsafety", &Present);
+        }
+        if self.value.auto_token.is_some() {
+            formatter.field("auto_token", &Present);
+        }
+        if let Some(val) = &self.value.restriction {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::ImplRestriction);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("restriction", Print::ref_cast(val));
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        if self.value.colon_token.is_some() {
+            formatter.field("colon_token", &Present);
+        }
+        if !self.value.supertraits.is_empty() {
+            formatter.field("supertraits", Lite(&self.value.supertraits));
+        }
+        if !self.value.items.is_empty() {
+            formatter.field("items", Lite(&self.value.items));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemTraitAlias> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemTraitAlias");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemType");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemUnion> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemUnion");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.field("fields", Lite(&self.value.fields));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ItemUse> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ItemUse");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("vis", Lite(&self.value.vis));
+        if self.value.leading_colon.is_some() {
+            formatter.field("leading_colon", &Present);
+        }
+        formatter.field("tree", Lite(&self.value.tree));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Label> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Label");
+        formatter.field("name", Lite(&self.value.name));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Lifetime> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Lifetime");
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::LifetimeParam> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("LifetimeParam");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("lifetime", Lite(&self.value.lifetime));
+        if self.value.colon_token.is_some() {
+            formatter.field("colon_token", &Present);
+        }
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Lit> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Lit::Str(_val) => write!(formatter, "{:?}", _val.value()),
+            syn::Lit::ByteStr(_val) => write!(formatter, "{:?}", _val.value()),
+            syn::Lit::Byte(_val) => write!(formatter, "{:?}", _val.value()),
+            syn::Lit::Char(_val) => write!(formatter, "{:?}", _val.value()),
+            syn::Lit::Int(_val) => write!(formatter, "{}", _val),
+            syn::Lit::Float(_val) => write!(formatter, "{}", _val),
+            syn::Lit::Bool(_val) => {
+                let mut formatter = formatter.debug_struct("Lit::Bool");
+                formatter.field("value", Lite(&_val.value));
+                formatter.finish()
+            }
+            syn::Lit::Verbatim(_val) => {
+                formatter.write_str("Lit::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::LitBool> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("LitBool");
+        formatter.field("value", Lite(&self.value.value));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::LitByte> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{:?}", self.value.value())
+    }
+}
+impl Debug for Lite<syn::LitByteStr> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{:?}", self.value.value())
+    }
+}
+impl Debug for Lite<syn::LitChar> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{:?}", self.value.value())
+    }
+}
+impl Debug for Lite<syn::LitFloat> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{}", & self.value)
+    }
+}
+impl Debug for Lite<syn::LitInt> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{}", & self.value)
+    }
+}
+impl Debug for Lite<syn::LitStr> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{:?}", self.value.value())
+    }
+}
+impl Debug for Lite<syn::Local> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Local");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("pat", Lite(&self.value.pat));
+        if let Some(val) = &self.value.init {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::LocalInit);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("init", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::LocalInit> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("LocalInit");
+        formatter.field("expr", Lite(&self.value.expr));
+        if let Some(val) = &self.value.diverge {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::Else, Box<syn::Expr>));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("diverge", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Macro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Macro");
+        formatter.field("path", Lite(&self.value.path));
+        formatter.field("delimiter", Lite(&self.value.delimiter));
+        formatter.field("tokens", Lite(&self.value.tokens));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::MacroDelimiter> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::MacroDelimiter::Paren(_val) => {
+                formatter.write_str("MacroDelimiter::Paren")?;
+                Ok(())
+            }
+            syn::MacroDelimiter::Brace(_val) => {
+                formatter.write_str("MacroDelimiter::Brace")?;
+                Ok(())
+            }
+            syn::MacroDelimiter::Bracket(_val) => {
+                formatter.write_str("MacroDelimiter::Bracket")?;
+                Ok(())
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::Member> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Member::Named(_val) => {
+                formatter.write_str("Member::Named")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::Member::Unnamed(_val) => {
+                formatter.write_str("Member::Unnamed")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::Meta> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Meta::Path(_val) => {
+                let mut formatter = formatter.debug_struct("Meta::Path");
+                if _val.leading_colon.is_some() {
+                    formatter.field("leading_colon", &Present);
+                }
+                if !_val.segments.is_empty() {
+                    formatter.field("segments", Lite(&_val.segments));
+                }
+                formatter.finish()
+            }
+            syn::Meta::List(_val) => {
+                let mut formatter = formatter.debug_struct("Meta::List");
+                formatter.field("path", Lite(&_val.path));
+                formatter.field("delimiter", Lite(&_val.delimiter));
+                formatter.field("tokens", Lite(&_val.tokens));
+                formatter.finish()
+            }
+            syn::Meta::NameValue(_val) => {
+                let mut formatter = formatter.debug_struct("Meta::NameValue");
+                formatter.field("path", Lite(&_val.path));
+                formatter.field("value", Lite(&_val.value));
+                formatter.finish()
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::MetaList> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("MetaList");
+        formatter.field("path", Lite(&self.value.path));
+        formatter.field("delimiter", Lite(&self.value.delimiter));
+        formatter.field("tokens", Lite(&self.value.tokens));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::MetaNameValue> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("MetaNameValue");
+        formatter.field("path", Lite(&self.value.path));
+        formatter.field("value", Lite(&self.value.value));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ParenthesizedGenericArguments> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("ParenthesizedGenericArguments");
+        if !self.value.inputs.is_empty() {
+            formatter.field("inputs", Lite(&self.value.inputs));
+        }
+        formatter.field("output", Lite(&self.value.output));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Pat> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Pat::Const(_val) => {
+                formatter.write_str("Pat::Const")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::Pat::Ident(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Ident");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if _val.by_ref.is_some() {
+                    formatter.field("by_ref", &Present);
+                }
+                if _val.mutability.is_some() {
+                    formatter.field("mutability", &Present);
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                if let Some(val) = &_val.subpat {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print((syn::token::At, Box<syn::Pat>));
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0.1), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("subpat", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Pat::Lit(_val) => {
+                formatter.write_str("Pat::Lit")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::Pat::Macro(_val) => {
+                formatter.write_str("Pat::Macro")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::Pat::Or(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Or");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if _val.leading_vert.is_some() {
+                    formatter.field("leading_vert", &Present);
+                }
+                if !_val.cases.is_empty() {
+                    formatter.field("cases", Lite(&_val.cases));
+                }
+                formatter.finish()
+            }
+            syn::Pat::Paren(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Paren");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("pat", Lite(&_val.pat));
+                formatter.finish()
+            }
+            syn::Pat::Path(_val) => {
+                formatter.write_str("Pat::Path")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::Pat::Range(_val) => {
+                formatter.write_str("Pat::Range")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::Pat::Reference(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Reference");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if _val.mutability.is_some() {
+                    formatter.field("mutability", &Present);
+                }
+                formatter.field("pat", Lite(&_val.pat));
+                formatter.finish()
+            }
+            syn::Pat::Rest(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Rest");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.finish()
+            }
+            syn::Pat::Slice(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Slice");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if !_val.elems.is_empty() {
+                    formatter.field("elems", Lite(&_val.elems));
+                }
+                formatter.finish()
+            }
+            syn::Pat::Struct(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Struct");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.qself {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::QSelf);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("qself", Print::ref_cast(val));
+                }
+                formatter.field("path", Lite(&_val.path));
+                if !_val.fields.is_empty() {
+                    formatter.field("fields", Lite(&_val.fields));
+                }
+                if let Some(val) = &_val.rest {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::PatRest);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("rest", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Pat::Tuple(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Tuple");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if !_val.elems.is_empty() {
+                    formatter.field("elems", Lite(&_val.elems));
+                }
+                formatter.finish()
+            }
+            syn::Pat::TupleStruct(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::TupleStruct");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                if let Some(val) = &_val.qself {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::QSelf);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("qself", Print::ref_cast(val));
+                }
+                formatter.field("path", Lite(&_val.path));
+                if !_val.elems.is_empty() {
+                    formatter.field("elems", Lite(&_val.elems));
+                }
+                formatter.finish()
+            }
+            syn::Pat::Type(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Type");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("pat", Lite(&_val.pat));
+                formatter.field("ty", Lite(&_val.ty));
+                formatter.finish()
+            }
+            syn::Pat::Verbatim(_val) => {
+                formatter.write_str("Pat::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            syn::Pat::Wild(_val) => {
+                let mut formatter = formatter.debug_struct("Pat::Wild");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.finish()
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::PatIdent> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatIdent");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if self.value.by_ref.is_some() {
+            formatter.field("by_ref", &Present);
+        }
+        if self.value.mutability.is_some() {
+            formatter.field("mutability", &Present);
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        if let Some(val) = &self.value.subpat {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::At, Box<syn::Pat>));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("subpat", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatOr> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatOr");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if self.value.leading_vert.is_some() {
+            formatter.field("leading_vert", &Present);
+        }
+        if !self.value.cases.is_empty() {
+            formatter.field("cases", Lite(&self.value.cases));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatParen> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatParen");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("pat", Lite(&self.value.pat));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatReference> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatReference");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if self.value.mutability.is_some() {
+            formatter.field("mutability", &Present);
+        }
+        formatter.field("pat", Lite(&self.value.pat));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatRest> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatRest");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatSlice> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatSlice");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if !self.value.elems.is_empty() {
+            formatter.field("elems", Lite(&self.value.elems));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatStruct> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatStruct");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.qself {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::QSelf);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("qself", Print::ref_cast(val));
+        }
+        formatter.field("path", Lite(&self.value.path));
+        if !self.value.fields.is_empty() {
+            formatter.field("fields", Lite(&self.value.fields));
+        }
+        if let Some(val) = &self.value.rest {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::PatRest);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("rest", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatTuple> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatTuple");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if !self.value.elems.is_empty() {
+            formatter.field("elems", Lite(&self.value.elems));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatTupleStruct> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatTupleStruct");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.qself {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::QSelf);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("qself", Print::ref_cast(val));
+        }
+        formatter.field("path", Lite(&self.value.path));
+        if !self.value.elems.is_empty() {
+            formatter.field("elems", Lite(&self.value.elems));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatType");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("pat", Lite(&self.value.pat));
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PatWild> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PatWild");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Path> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Path");
+        if self.value.leading_colon.is_some() {
+            formatter.field("leading_colon", &Present);
+        }
+        if !self.value.segments.is_empty() {
+            formatter.field("segments", Lite(&self.value.segments));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PathArguments> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::PathArguments::None => formatter.write_str("PathArguments::None"),
+            syn::PathArguments::AngleBracketed(_val) => {
+                let mut formatter = formatter
+                    .debug_struct("PathArguments::AngleBracketed");
+                if _val.colon2_token.is_some() {
+                    formatter.field("colon2_token", &Present);
+                }
+                if !_val.args.is_empty() {
+                    formatter.field("args", Lite(&_val.args));
+                }
+                formatter.finish()
+            }
+            syn::PathArguments::Parenthesized(_val) => {
+                let mut formatter = formatter
+                    .debug_struct("PathArguments::Parenthesized");
+                if !_val.inputs.is_empty() {
+                    formatter.field("inputs", Lite(&_val.inputs));
+                }
+                formatter.field("output", Lite(&_val.output));
+                formatter.finish()
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::PathSegment> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PathSegment");
+        formatter.field("ident", Lite(&self.value.ident));
+        match self.value.arguments {
+            syn::PathArguments::None => {}
+            _ => {
+                formatter.field("arguments", Lite(&self.value.arguments));
+            }
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PredicateLifetime> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PredicateLifetime");
+        formatter.field("lifetime", Lite(&self.value.lifetime));
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::PredicateType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("PredicateType");
+        if let Some(val) = &self.value.lifetimes {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::BoundLifetimes);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("lifetimes", Print::ref_cast(val));
+        }
+        formatter.field("bounded_ty", Lite(&self.value.bounded_ty));
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::QSelf> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("QSelf");
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.field("position", Lite(&self.value.position));
+        if self.value.as_token.is_some() {
+            formatter.field("as_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::RangeLimits> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::RangeLimits::HalfOpen(_val) => {
+                formatter.write_str("RangeLimits::HalfOpen")?;
+                Ok(())
+            }
+            syn::RangeLimits::Closed(_val) => {
+                formatter.write_str("RangeLimits::Closed")?;
+                Ok(())
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::Receiver> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Receiver");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.reference {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::And, Option<syn::Lifetime>));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(
+                        {
+                            #[derive(RefCast)]
+                            #[repr(transparent)]
+                            struct Print(Option<syn::Lifetime>);
+                            impl Debug for Print {
+                                fn fmt(
+                                    &self,
+                                    formatter: &mut fmt::Formatter,
+                                ) -> fmt::Result {
+                                    match &self.0 {
+                                        Some(_val) => {
+                                            formatter.write_str("Some(")?;
+                                            Debug::fmt(Lite(_val), formatter)?;
+                                            formatter.write_str(")")?;
+                                            Ok(())
+                                        }
+                                        None => formatter.write_str("None"),
+                                    }
+                                }
+                            }
+                            Print::ref_cast(&self.0.1)
+                        },
+                        formatter,
+                    )?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("reference", Print::ref_cast(val));
+        }
+        if self.value.mutability.is_some() {
+            formatter.field("mutability", &Present);
+        }
+        if self.value.colon_token.is_some() {
+            formatter.field("colon_token", &Present);
+        }
+        formatter.field("ty", Lite(&self.value.ty));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::ReturnType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::ReturnType::Default => formatter.write_str("ReturnType::Default"),
+            syn::ReturnType::Type(_v0, _v1) => {
+                let mut formatter = formatter.debug_tuple("ReturnType::Type");
+                formatter.field(Lite(_v1));
+                formatter.finish()
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::Signature> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Signature");
+        if self.value.constness.is_some() {
+            formatter.field("constness", &Present);
+        }
+        if self.value.asyncness.is_some() {
+            formatter.field("asyncness", &Present);
+        }
+        if self.value.unsafety.is_some() {
+            formatter.field("unsafety", &Present);
+        }
+        if let Some(val) = &self.value.abi {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Abi);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("abi", Print::ref_cast(val));
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        if !self.value.inputs.is_empty() {
+            formatter.field("inputs", Lite(&self.value.inputs));
+        }
+        if let Some(val) = &self.value.variadic {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Variadic);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("variadic", Print::ref_cast(val));
+        }
+        formatter.field("output", Lite(&self.value.output));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::StaticMutability> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::StaticMutability::Mut(_val) => {
+                formatter.write_str("StaticMutability::Mut")?;
+                Ok(())
+            }
+            syn::StaticMutability::None => formatter.write_str("StaticMutability::None"),
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::Stmt> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Stmt::Local(_val) => {
+                let mut formatter = formatter.debug_struct("Stmt::Local");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("pat", Lite(&_val.pat));
+                if let Some(val) = &_val.init {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::LocalInit);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("init", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::Stmt::Item(_val) => {
+                formatter.write_str("Stmt::Item")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::Stmt::Expr(_v0, _v1) => {
+                let mut formatter = formatter.debug_tuple("Stmt::Expr");
+                formatter.field(Lite(_v0));
+                formatter
+                    .field(
+                        &super::Option {
+                            present: _v1.is_some(),
+                        },
+                    );
+                formatter.finish()
+            }
+            syn::Stmt::Macro(_val) => {
+                let mut formatter = formatter.debug_struct("Stmt::Macro");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("mac", Lite(&_val.mac));
+                if _val.semi_token.is_some() {
+                    formatter.field("semi_token", &Present);
+                }
+                formatter.finish()
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::StmtMacro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("StmtMacro");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("mac", Lite(&self.value.mac));
+        if self.value.semi_token.is_some() {
+            formatter.field("semi_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TraitBound> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TraitBound");
+        if self.value.paren_token.is_some() {
+            formatter.field("paren_token", &Present);
+        }
+        match self.value.modifier {
+            syn::TraitBoundModifier::None => {}
+            _ => {
+                formatter.field("modifier", Lite(&self.value.modifier));
+            }
+        }
+        if let Some(val) = &self.value.lifetimes {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::BoundLifetimes);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("lifetimes", Print::ref_cast(val));
+        }
+        formatter.field("path", Lite(&self.value.path));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TraitBoundModifier> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::TraitBoundModifier::None => {
+                formatter.write_str("TraitBoundModifier::None")
+            }
+            syn::TraitBoundModifier::Maybe(_val) => {
+                formatter.write_str("TraitBoundModifier::Maybe")?;
+                Ok(())
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::TraitItem> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::TraitItem::Const(_val) => {
+                let mut formatter = formatter.debug_struct("TraitItem::Const");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                formatter.field("ty", Lite(&_val.ty));
+                if let Some(val) = &_val.default {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print((syn::token::Eq, syn::Expr));
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0.1), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("default", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::TraitItem::Fn(_val) => {
+                let mut formatter = formatter.debug_struct("TraitItem::Fn");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("sig", Lite(&_val.sig));
+                if let Some(val) = &_val.default {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Block);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("default", Print::ref_cast(val));
+                }
+                if _val.semi_token.is_some() {
+                    formatter.field("semi_token", &Present);
+                }
+                formatter.finish()
+            }
+            syn::TraitItem::Type(_val) => {
+                let mut formatter = formatter.debug_struct("TraitItem::Type");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.field("generics", Lite(&_val.generics));
+                if _val.colon_token.is_some() {
+                    formatter.field("colon_token", &Present);
+                }
+                if !_val.bounds.is_empty() {
+                    formatter.field("bounds", Lite(&_val.bounds));
+                }
+                if let Some(val) = &_val.default {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print((syn::token::Eq, syn::Type));
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0.1), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("default", Print::ref_cast(val));
+                }
+                formatter.finish()
+            }
+            syn::TraitItem::Macro(_val) => {
+                let mut formatter = formatter.debug_struct("TraitItem::Macro");
+                if !_val.attrs.is_empty() {
+                    formatter.field("attrs", Lite(&_val.attrs));
+                }
+                formatter.field("mac", Lite(&_val.mac));
+                if _val.semi_token.is_some() {
+                    formatter.field("semi_token", &Present);
+                }
+                formatter.finish()
+            }
+            syn::TraitItem::Verbatim(_val) => {
+                formatter.write_str("TraitItem::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::TraitItemConst> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TraitItemConst");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        formatter.field("ty", Lite(&self.value.ty));
+        if let Some(val) = &self.value.default {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::Eq, syn::Expr));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("default", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TraitItemFn> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TraitItemFn");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("sig", Lite(&self.value.sig));
+        if let Some(val) = &self.value.default {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Block);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("default", Print::ref_cast(val));
+        }
+        if self.value.semi_token.is_some() {
+            formatter.field("semi_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TraitItemMacro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TraitItemMacro");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("mac", Lite(&self.value.mac));
+        if self.value.semi_token.is_some() {
+            formatter.field("semi_token", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TraitItemType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TraitItemType");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("generics", Lite(&self.value.generics));
+        if self.value.colon_token.is_some() {
+            formatter.field("colon_token", &Present);
+        }
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        if let Some(val) = &self.value.default {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::Eq, syn::Type));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("default", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Type> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Type::Array(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Array");
+                formatter.field("elem", Lite(&_val.elem));
+                formatter.field("len", Lite(&_val.len));
+                formatter.finish()
+            }
+            syn::Type::BareFn(_val) => {
+                let mut formatter = formatter.debug_struct("Type::BareFn");
+                if let Some(val) = &_val.lifetimes {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::BoundLifetimes);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("lifetimes", Print::ref_cast(val));
+                }
+                if _val.unsafety.is_some() {
+                    formatter.field("unsafety", &Present);
+                }
+                if let Some(val) = &_val.abi {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Abi);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("abi", Print::ref_cast(val));
+                }
+                if !_val.inputs.is_empty() {
+                    formatter.field("inputs", Lite(&_val.inputs));
+                }
+                if let Some(val) = &_val.variadic {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::BareVariadic);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("variadic", Print::ref_cast(val));
+                }
+                formatter.field("output", Lite(&_val.output));
+                formatter.finish()
+            }
+            syn::Type::Group(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Group");
+                formatter.field("elem", Lite(&_val.elem));
+                formatter.finish()
+            }
+            syn::Type::ImplTrait(_val) => {
+                let mut formatter = formatter.debug_struct("Type::ImplTrait");
+                if !_val.bounds.is_empty() {
+                    formatter.field("bounds", Lite(&_val.bounds));
+                }
+                formatter.finish()
+            }
+            syn::Type::Infer(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Infer");
+                formatter.finish()
+            }
+            syn::Type::Macro(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Macro");
+                formatter.field("mac", Lite(&_val.mac));
+                formatter.finish()
+            }
+            syn::Type::Never(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Never");
+                formatter.finish()
+            }
+            syn::Type::Paren(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Paren");
+                formatter.field("elem", Lite(&_val.elem));
+                formatter.finish()
+            }
+            syn::Type::Path(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Path");
+                if let Some(val) = &_val.qself {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::QSelf);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("qself", Print::ref_cast(val));
+                }
+                formatter.field("path", Lite(&_val.path));
+                formatter.finish()
+            }
+            syn::Type::Ptr(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Ptr");
+                if _val.const_token.is_some() {
+                    formatter.field("const_token", &Present);
+                }
+                if _val.mutability.is_some() {
+                    formatter.field("mutability", &Present);
+                }
+                formatter.field("elem", Lite(&_val.elem));
+                formatter.finish()
+            }
+            syn::Type::Reference(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Reference");
+                if let Some(val) = &_val.lifetime {
+                    #[derive(RefCast)]
+                    #[repr(transparent)]
+                    struct Print(syn::Lifetime);
+                    impl Debug for Print {
+                        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                            formatter.write_str("Some(")?;
+                            Debug::fmt(Lite(&self.0), formatter)?;
+                            formatter.write_str(")")?;
+                            Ok(())
+                        }
+                    }
+                    formatter.field("lifetime", Print::ref_cast(val));
+                }
+                if _val.mutability.is_some() {
+                    formatter.field("mutability", &Present);
+                }
+                formatter.field("elem", Lite(&_val.elem));
+                formatter.finish()
+            }
+            syn::Type::Slice(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Slice");
+                formatter.field("elem", Lite(&_val.elem));
+                formatter.finish()
+            }
+            syn::Type::TraitObject(_val) => {
+                let mut formatter = formatter.debug_struct("Type::TraitObject");
+                if _val.dyn_token.is_some() {
+                    formatter.field("dyn_token", &Present);
+                }
+                if !_val.bounds.is_empty() {
+                    formatter.field("bounds", Lite(&_val.bounds));
+                }
+                formatter.finish()
+            }
+            syn::Type::Tuple(_val) => {
+                let mut formatter = formatter.debug_struct("Type::Tuple");
+                if !_val.elems.is_empty() {
+                    formatter.field("elems", Lite(&_val.elems));
+                }
+                formatter.finish()
+            }
+            syn::Type::Verbatim(_val) => {
+                formatter.write_str("Type::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::TypeArray> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeArray");
+        formatter.field("elem", Lite(&self.value.elem));
+        formatter.field("len", Lite(&self.value.len));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeBareFn> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeBareFn");
+        if let Some(val) = &self.value.lifetimes {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::BoundLifetimes);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("lifetimes", Print::ref_cast(val));
+        }
+        if self.value.unsafety.is_some() {
+            formatter.field("unsafety", &Present);
+        }
+        if let Some(val) = &self.value.abi {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Abi);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("abi", Print::ref_cast(val));
+        }
+        if !self.value.inputs.is_empty() {
+            formatter.field("inputs", Lite(&self.value.inputs));
+        }
+        if let Some(val) = &self.value.variadic {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::BareVariadic);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("variadic", Print::ref_cast(val));
+        }
+        formatter.field("output", Lite(&self.value.output));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeGroup> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeGroup");
+        formatter.field("elem", Lite(&self.value.elem));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeImplTrait> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeImplTrait");
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeInfer> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeInfer");
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeMacro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeMacro");
+        formatter.field("mac", Lite(&self.value.mac));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeNever> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeNever");
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeParam> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeParam");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        if self.value.colon_token.is_some() {
+            formatter.field("colon_token", &Present);
+        }
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        if self.value.eq_token.is_some() {
+            formatter.field("eq_token", &Present);
+        }
+        if let Some(val) = &self.value.default {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Type);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("default", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeParamBound> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::TypeParamBound::Trait(_val) => {
+                formatter.write_str("TypeParamBound::Trait")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::TypeParamBound::Lifetime(_val) => {
+                let mut formatter = formatter.debug_struct("TypeParamBound::Lifetime");
+                formatter.field("ident", Lite(&_val.ident));
+                formatter.finish()
+            }
+            syn::TypeParamBound::Verbatim(_val) => {
+                formatter.write_str("TypeParamBound::Verbatim")?;
+                formatter.write_str("(`")?;
+                Display::fmt(_val, formatter)?;
+                formatter.write_str("`)")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::TypeParen> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeParen");
+        formatter.field("elem", Lite(&self.value.elem));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypePath> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypePath");
+        if let Some(val) = &self.value.qself {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::QSelf);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("qself", Print::ref_cast(val));
+        }
+        formatter.field("path", Lite(&self.value.path));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypePtr> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypePtr");
+        if self.value.const_token.is_some() {
+            formatter.field("const_token", &Present);
+        }
+        if self.value.mutability.is_some() {
+            formatter.field("mutability", &Present);
+        }
+        formatter.field("elem", Lite(&self.value.elem));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeReference> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeReference");
+        if let Some(val) = &self.value.lifetime {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print(syn::Lifetime);
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("lifetime", Print::ref_cast(val));
+        }
+        if self.value.mutability.is_some() {
+            formatter.field("mutability", &Present);
+        }
+        formatter.field("elem", Lite(&self.value.elem));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeSlice> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeSlice");
+        formatter.field("elem", Lite(&self.value.elem));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeTraitObject> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeTraitObject");
+        if self.value.dyn_token.is_some() {
+            formatter.field("dyn_token", &Present);
+        }
+        if !self.value.bounds.is_empty() {
+            formatter.field("bounds", Lite(&self.value.bounds));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::TypeTuple> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("TypeTuple");
+        if !self.value.elems.is_empty() {
+            formatter.field("elems", Lite(&self.value.elems));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::UnOp> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::UnOp::Deref(_val) => {
+                formatter.write_str("UnOp::Deref")?;
+                Ok(())
+            }
+            syn::UnOp::Not(_val) => {
+                formatter.write_str("UnOp::Not")?;
+                Ok(())
+            }
+            syn::UnOp::Neg(_val) => {
+                formatter.write_str("UnOp::Neg")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::UseGlob> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("UseGlob");
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::UseGroup> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("UseGroup");
+        if !self.value.items.is_empty() {
+            formatter.field("items", Lite(&self.value.items));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::UseName> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("UseName");
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::UsePath> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("UsePath");
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("tree", Lite(&self.value.tree));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::UseRename> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("UseRename");
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("rename", Lite(&self.value.rename));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::UseTree> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::UseTree::Path(_val) => {
+                formatter.write_str("UseTree::Path")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::UseTree::Name(_val) => {
+                formatter.write_str("UseTree::Name")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::UseTree::Rename(_val) => {
+                formatter.write_str("UseTree::Rename")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::UseTree::Glob(_val) => {
+                formatter.write_str("UseTree::Glob")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::UseTree::Group(_val) => {
+                formatter.write_str("UseTree::Group")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+        }
+    }
+}
+impl Debug for Lite<syn::Variadic> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Variadic");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        if let Some(val) = &self.value.pat {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((Box<syn::Pat>, syn::token::Colon));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.0), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("pat", Print::ref_cast(val));
+        }
+        if self.value.comma.is_some() {
+            formatter.field("comma", &Present);
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Variant> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("Variant");
+        if !self.value.attrs.is_empty() {
+            formatter.field("attrs", Lite(&self.value.attrs));
+        }
+        formatter.field("ident", Lite(&self.value.ident));
+        formatter.field("fields", Lite(&self.value.fields));
+        if let Some(val) = &self.value.discriminant {
+            #[derive(RefCast)]
+            #[repr(transparent)]
+            struct Print((syn::token::Eq, syn::Expr));
+            impl Debug for Print {
+                fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("Some(")?;
+                    Debug::fmt(Lite(&self.0.1), formatter)?;
+                    formatter.write_str(")")?;
+                    Ok(())
+                }
+            }
+            formatter.field("discriminant", Print::ref_cast(val));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::VisRestricted> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("VisRestricted");
+        if self.value.in_token.is_some() {
+            formatter.field("in_token", &Present);
+        }
+        formatter.field("path", Lite(&self.value.path));
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::Visibility> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::Visibility::Public(_val) => {
+                formatter.write_str("Visibility::Public")?;
+                Ok(())
+            }
+            syn::Visibility::Restricted(_val) => {
+                let mut formatter = formatter.debug_struct("Visibility::Restricted");
+                if _val.in_token.is_some() {
+                    formatter.field("in_token", &Present);
+                }
+                formatter.field("path", Lite(&_val.path));
+                formatter.finish()
+            }
+            syn::Visibility::Inherited => formatter.write_str("Visibility::Inherited"),
+        }
+    }
+}
+impl Debug for Lite<syn::WhereClause> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut formatter = formatter.debug_struct("WhereClause");
+        if !self.value.predicates.is_empty() {
+            formatter.field("predicates", Lite(&self.value.predicates));
+        }
+        formatter.finish()
+    }
+}
+impl Debug for Lite<syn::WherePredicate> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.value {
+            syn::WherePredicate::Lifetime(_val) => {
+                formatter.write_str("WherePredicate::Lifetime")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            syn::WherePredicate::Type(_val) => {
+                formatter.write_str("WherePredicate::Type")?;
+                formatter.write_str("(")?;
+                Debug::fmt(Lite(_val), formatter)?;
+                formatter.write_str(")")?;
+                Ok(())
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+impl Debug for Lite<syn::token::Abstract> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![abstract]")
+    }
+}
+impl Debug for Lite<syn::token::And> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![&]")
+    }
+}
+impl Debug for Lite<syn::token::AndAnd> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![&&]")
+    }
+}
+impl Debug for Lite<syn::token::AndEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![&=]")
+    }
+}
+impl Debug for Lite<syn::token::As> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![as]")
+    }
+}
+impl Debug for Lite<syn::token::Async> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![async]")
+    }
+}
+impl Debug for Lite<syn::token::At> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![@]")
+    }
+}
+impl Debug for Lite<syn::token::Auto> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![auto]")
+    }
+}
+impl Debug for Lite<syn::token::Await> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![await]")
+    }
+}
+impl Debug for Lite<syn::token::Become> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![become]")
+    }
+}
+impl Debug for Lite<syn::token::Box> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![box]")
+    }
+}
+impl Debug for Lite<syn::token::Break> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![break]")
+    }
+}
+impl Debug for Lite<syn::token::Caret> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![^]")
+    }
+}
+impl Debug for Lite<syn::token::CaretEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![^=]")
+    }
+}
+impl Debug for Lite<syn::token::Colon> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![:]")
+    }
+}
+impl Debug for Lite<syn::token::Comma> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![,]")
+    }
+}
+impl Debug for Lite<syn::token::Const> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![const]")
+    }
+}
+impl Debug for Lite<syn::token::Continue> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![continue]")
+    }
+}
+impl Debug for Lite<syn::token::Crate> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![crate]")
+    }
+}
+impl Debug for Lite<syn::token::Default> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![default]")
+    }
+}
+impl Debug for Lite<syn::token::Do> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![do]")
+    }
+}
+impl Debug for Lite<syn::token::Dollar> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![$]")
+    }
+}
+impl Debug for Lite<syn::token::Dot> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![.]")
+    }
+}
+impl Debug for Lite<syn::token::DotDot> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![..]")
+    }
+}
+impl Debug for Lite<syn::token::DotDotDot> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![...]")
+    }
+}
+impl Debug for Lite<syn::token::DotDotEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![..=]")
+    }
+}
+impl Debug for Lite<syn::token::Dyn> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![dyn]")
+    }
+}
+impl Debug for Lite<syn::token::Else> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![else]")
+    }
+}
+impl Debug for Lite<syn::token::Enum> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![enum]")
+    }
+}
+impl Debug for Lite<syn::token::Eq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![=]")
+    }
+}
+impl Debug for Lite<syn::token::EqEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![==]")
+    }
+}
+impl Debug for Lite<syn::token::Extern> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![extern]")
+    }
+}
+impl Debug for Lite<syn::token::FatArrow> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![=>]")
+    }
+}
+impl Debug for Lite<syn::token::Final> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![final]")
+    }
+}
+impl Debug for Lite<syn::token::Fn> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![fn]")
+    }
+}
+impl Debug for Lite<syn::token::For> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![for]")
+    }
+}
+impl Debug for Lite<syn::token::Ge> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![>=]")
+    }
+}
+impl Debug for Lite<syn::token::Gt> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![>]")
+    }
+}
+impl Debug for Lite<syn::token::If> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![if]")
+    }
+}
+impl Debug for Lite<syn::token::Impl> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![impl]")
+    }
+}
+impl Debug for Lite<syn::token::In> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![in]")
+    }
+}
+impl Debug for Lite<syn::token::LArrow> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![<-]")
+    }
+}
+impl Debug for Lite<syn::token::Le> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![<=]")
+    }
+}
+impl Debug for Lite<syn::token::Let> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![let]")
+    }
+}
+impl Debug for Lite<syn::token::Loop> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![loop]")
+    }
+}
+impl Debug for Lite<syn::token::Lt> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![<]")
+    }
+}
+impl Debug for Lite<syn::token::Macro> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![macro]")
+    }
+}
+impl Debug for Lite<syn::token::Match> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![match]")
+    }
+}
+impl Debug for Lite<syn::token::Minus> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![-]")
+    }
+}
+impl Debug for Lite<syn::token::MinusEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![-=]")
+    }
+}
+impl Debug for Lite<syn::token::Mod> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![mod]")
+    }
+}
+impl Debug for Lite<syn::token::Move> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![move]")
+    }
+}
+impl Debug for Lite<syn::token::Mut> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![mut]")
+    }
+}
+impl Debug for Lite<syn::token::Ne> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![!=]")
+    }
+}
+impl Debug for Lite<syn::token::Not> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![!]")
+    }
+}
+impl Debug for Lite<syn::token::Or> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![|]")
+    }
+}
+impl Debug for Lite<syn::token::OrEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![|=]")
+    }
+}
+impl Debug for Lite<syn::token::OrOr> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![||]")
+    }
+}
+impl Debug for Lite<syn::token::Override> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![override]")
+    }
+}
+impl Debug for Lite<syn::token::PathSep> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![::]")
+    }
+}
+impl Debug for Lite<syn::token::Percent> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![%]")
+    }
+}
+impl Debug for Lite<syn::token::PercentEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![%=]")
+    }
+}
+impl Debug for Lite<syn::token::Plus> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![+]")
+    }
+}
+impl Debug for Lite<syn::token::PlusEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![+=]")
+    }
+}
+impl Debug for Lite<syn::token::Pound> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![#]")
+    }
+}
+impl Debug for Lite<syn::token::Priv> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![priv]")
+    }
+}
+impl Debug for Lite<syn::token::Pub> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![pub]")
+    }
+}
+impl Debug for Lite<syn::token::Question> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![?]")
+    }
+}
+impl Debug for Lite<syn::token::RArrow> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![->]")
+    }
+}
+impl Debug for Lite<syn::token::Ref> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![ref]")
+    }
+}
+impl Debug for Lite<syn::token::Return> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![return]")
+    }
+}
+impl Debug for Lite<syn::token::SelfType> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![Self]")
+    }
+}
+impl Debug for Lite<syn::token::SelfValue> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![self]")
+    }
+}
+impl Debug for Lite<syn::token::Semi> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![;]")
+    }
+}
+impl Debug for Lite<syn::token::Shl> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![<<]")
+    }
+}
+impl Debug for Lite<syn::token::ShlEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![<<=]")
+    }
+}
+impl Debug for Lite<syn::token::Shr> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![>>]")
+    }
+}
+impl Debug for Lite<syn::token::ShrEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![>>=]")
+    }
+}
+impl Debug for Lite<syn::token::Slash> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![/]")
+    }
+}
+impl Debug for Lite<syn::token::SlashEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![/=]")
+    }
+}
+impl Debug for Lite<syn::token::Star> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![*]")
+    }
+}
+impl Debug for Lite<syn::token::StarEq> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![*=]")
+    }
+}
+impl Debug for Lite<syn::token::Static> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![static]")
+    }
+}
+impl Debug for Lite<syn::token::Struct> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![struct]")
+    }
+}
+impl Debug for Lite<syn::token::Super> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![super]")
+    }
+}
+impl Debug for Lite<syn::token::Tilde> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![~]")
+    }
+}
+impl Debug for Lite<syn::token::Trait> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![trait]")
+    }
+}
+impl Debug for Lite<syn::token::Try> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![try]")
+    }
+}
+impl Debug for Lite<syn::token::Type> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![type]")
+    }
+}
+impl Debug for Lite<syn::token::Typeof> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![typeof]")
+    }
+}
+impl Debug for Lite<syn::token::Underscore> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![_]")
+    }
+}
+impl Debug for Lite<syn::token::Union> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![union]")
+    }
+}
+impl Debug for Lite<syn::token::Unsafe> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![unsafe]")
+    }
+}
+impl Debug for Lite<syn::token::Unsized> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![unsized]")
+    }
+}
+impl Debug for Lite<syn::token::Use> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![use]")
+    }
+}
+impl Debug for Lite<syn::token::Virtual> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![virtual]")
+    }
+}
+impl Debug for Lite<syn::token::Where> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![where]")
+    }
+}
+impl Debug for Lite<syn::token::While> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![while]")
+    }
+}
+impl Debug for Lite<syn::token::Yield> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Token![yield]")
+    }
+}
diff --git a/third_party/rust/syn/tests/debug/mod.rs b/third_party/rust/syn/tests/debug/mod.rs
new file mode 100644
index 0000000000..c9925a6d5c
--- /dev/null
+++ b/third_party/rust/syn/tests/debug/mod.rs
@@ -0,0 +1,147 @@
+#![allow(
+    clippy::no_effect_underscore_binding,
+    clippy::too_many_lines,
+    clippy::used_underscore_binding
+)]
+
+#[rustfmt::skip]
+mod gen;
+
+use proc_macro2::{Ident, Literal, TokenStream};
+use ref_cast::RefCast;
+use std::fmt::{self, Debug};
+use std::ops::Deref;
+use syn::punctuated::Punctuated;
+
+#[derive(RefCast)]
+#[repr(transparent)]
+pub struct Lite<T: ?Sized> {
+    value: T,
+}
+
+#[allow(non_snake_case)]
+pub fn Lite<T: ?Sized>(value: &T) -> &Lite<T> {
+    Lite::ref_cast(value)
+}
+
+impl<T: ?Sized> Deref for Lite<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.value
+    }
+}
+
+impl Debug for Lite<bool> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{}", self.value)
+    }
+}
+
+impl Debug for Lite<u32> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{}", self.value)
+    }
+}
+
+impl Debug for Lite<usize> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{}", self.value)
+    }
+}
+
+impl Debug for Lite<String> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{:?}", self.value)
+    }
+}
+
+impl Debug for Lite<Ident> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{:?}", self.value.to_string())
+    }
+}
+
+impl Debug for Lite<Literal> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{}", self.value)
+    }
+}
+
+impl Debug for Lite<TokenStream> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let string = self.value.to_string();
+        if string.len() <= 80 {
+            write!(formatter, "TokenStream(`{}`)", self.value)
+        } else {
+            formatter
+                .debug_tuple("TokenStream")
+                .field(&format_args!("`{}`", string))
+                .finish()
+        }
+    }
+}
+
+impl<'a, T> Debug for Lite<&'a T>
+where
+    Lite<T>: Debug,
+{
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(Lite(self.value), formatter)
+    }
+}
+
+impl<T> Debug for Lite<Box<T>>
+where
+    Lite<T>: Debug,
+{
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        Debug::fmt(Lite(&*self.value), formatter)
+    }
+}
+
+impl<T> Debug for Lite<Vec<T>>
+where
+    Lite<T>: Debug,
+{
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_list()
+            .entries(self.value.iter().map(Lite))
+            .finish()
+    }
+}
+
+impl<T, P> Debug for Lite<Punctuated<T, P>>
+where
+    Lite<T>: Debug,
+    Lite<P>: Debug,
+{
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut list = formatter.debug_list();
+        for pair in self.pairs() {
+            let (node, punct) = pair.into_tuple();
+            list.entry(Lite(node));
+            list.entries(punct.map(Lite));
+        }
+        list.finish()
+    }
+}
+
+struct Present;
+
+impl Debug for Present {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Some")
+    }
+}
+
+struct Option {
+    present: bool,
+}
+
+impl Debug for Option {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str(if self.present { "Some" } else { "None" })
+    }
+}
diff --git a/third_party/rust/syn/tests/macros/mod.rs b/third_party/rust/syn/tests/macros/mod.rs
new file mode 100644
index 0000000000..d27c391339
--- /dev/null
+++ b/third_party/rust/syn/tests/macros/mod.rs
@@ -0,0 +1,92 @@
+#![allow(unused_macros, unused_macro_rules)]
+
+#[path = "../debug/mod.rs"]
+pub mod debug;
+
+use std::str::FromStr;
+use syn::parse::Result;
+
+macro_rules! errorf {
+    ($($tt:tt)*) => {{
+        use ::std::io::Write;
+        let stderr = ::std::io::stderr();
+        write!(stderr.lock(), $($tt)*).unwrap();
+    }};
+}
+
+macro_rules! punctuated {
+    ($($e:expr,)+) => {{
+        let mut seq = ::syn::punctuated::Punctuated::new();
+        $(
+            seq.push($e);
+        )+
+        seq
+    }};
+
+    ($($e:expr),+) => {
+        punctuated!($($e,)+)
+    };
+}
+
+macro_rules! snapshot {
+    ($($args:tt)*) => {
+        snapshot_impl!(() $($args)*)
+    };
+}
+
+macro_rules! snapshot_impl {
+    (($expr:ident) as $t:ty, @$snapshot:literal) => {
+        let tokens = crate::macros::TryIntoTokens::try_into_tokens($expr).unwrap();
+        let $expr: $t = syn::parse_quote!(#tokens);
+        let debug = crate::macros::debug::Lite(&$expr);
+        if !cfg!(miri) {
+            #[allow(clippy::needless_raw_string_hashes)] // https://github.com/mitsuhiko/insta/issues/389
+            {
+                insta::assert_debug_snapshot!(debug, @$snapshot);
+            }
+        }
+    };
+    (($($expr:tt)*) as $t:ty, @$snapshot:literal) => {{
+        let tokens = crate::macros::TryIntoTokens::try_into_tokens($($expr)*).unwrap();
+        let syntax_tree: $t = syn::parse_quote!(#tokens);
+        let debug = crate::macros::debug::Lite(&syntax_tree);
+        if !cfg!(miri) {
+            #[allow(clippy::needless_raw_string_hashes)]
+            {
+                insta::assert_debug_snapshot!(debug, @$snapshot);
+            }
+        }
+        syntax_tree
+    }};
+    (($($expr:tt)*) , @$snapshot:literal) => {{
+        let syntax_tree = $($expr)*;
+        let debug = crate::macros::debug::Lite(&syntax_tree);
+        if !cfg!(miri) {
+            #[allow(clippy::needless_raw_string_hashes)]
+            {
+                insta::assert_debug_snapshot!(debug, @$snapshot);
+            }
+        }
+        syntax_tree
+    }};
+    (($($expr:tt)*) $next:tt $($rest:tt)*) => {
+        snapshot_impl!(($($expr)* $next) $($rest)*)
+    };
+}
+
+pub trait TryIntoTokens {
+    fn try_into_tokens(self) -> Result<proc_macro2::TokenStream>;
+}
+
+impl<'a> TryIntoTokens for &'a str {
+    fn try_into_tokens(self) -> Result<proc_macro2::TokenStream> {
+        let tokens = proc_macro2::TokenStream::from_str(self)?;
+        Ok(tokens)
+    }
+}
+
+impl TryIntoTokens for proc_macro2::TokenStream {
+    fn try_into_tokens(self) -> Result<proc_macro2::TokenStream> {
+        Ok(self)
+    }
+}
diff --git a/third_party/rust/syn/tests/regression.rs b/third_party/rust/syn/tests/regression.rs
new file mode 100644
index 0000000000..5c7fcddc8d
--- /dev/null
+++ b/third_party/rust/syn/tests/regression.rs
@@ -0,0 +1,5 @@
+#![allow(clippy::let_underscore_untyped, clippy::uninlined_format_args)]
+
+mod regression {
+    automod::dir!("tests/regression");
+}
diff --git a/third_party/rust/syn/tests/regression/issue1108.rs b/third_party/rust/syn/tests/regression/issue1108.rs
new file mode 100644
index 0000000000..11a82adaad
--- /dev/null
+++ b/third_party/rust/syn/tests/regression/issue1108.rs
@@ -0,0 +1,5 @@
+#[test]
+fn issue1108() {
+    let data = "impl<x<>>::x for";
+    let _ = syn::parse_file(data);
+}
diff --git a/third_party/rust/syn/tests/regression/issue1235.rs b/third_party/rust/syn/tests/regression/issue1235.rs
new file mode 100644
index 0000000000..8836030664
--- /dev/null
+++ b/third_party/rust/syn/tests/regression/issue1235.rs
@@ -0,0 +1,32 @@
+use proc_macro2::{Delimiter, Group};
+use quote::quote;
+
+#[test]
+fn main() {
+    // Okay. Rustc allows top-level `static` with no value syntactically, but
+    // not semantically. Syn parses as Item::Verbatim.
+    let tokens = quote! {
+        pub static FOO: usize;
+        pub static BAR: usize;
+    };
+    let file = syn::parse2::<syn::File>(tokens).unwrap();
+    println!("{:#?}", file);
+
+    // Okay.
+    let inner = Group::new(
+        Delimiter::None,
+        quote!(static FOO: usize = 0; pub static BAR: usize = 0),
+    );
+    let tokens = quote!(pub #inner;);
+    let file = syn::parse2::<syn::File>(tokens).unwrap();
+    println!("{:#?}", file);
+
+    // Formerly parser crash.
+    let inner = Group::new(
+        Delimiter::None,
+        quote!(static FOO: usize; pub static BAR: usize),
+    );
+    let tokens = quote!(pub #inner;);
+    let file = syn::parse2::<syn::File>(tokens).unwrap();
+    println!("{:#?}", file);
+}
diff --git a/third_party/rust/syn/tests/repo/mod.rs b/third_party/rust/syn/tests/repo/mod.rs
new file mode 100644
index 0000000000..6aedd2ccdf
--- /dev/null
+++ b/third_party/rust/syn/tests/repo/mod.rs
@@ -0,0 +1,375 @@
+#![allow(clippy::manual_assert)]
+
+mod progress;
+
+use self::progress::Progress;
+use anyhow::Result;
+use flate2::read::GzDecoder;
+use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
+use std::collections::BTreeSet;
+use std::ffi::OsStr;
+use std::fs;
+use std::path::{Path, PathBuf};
+use tar::Archive;
+use walkdir::{DirEntry, WalkDir};
+
+const REVISION: &str = "b10cfcd65fd7f7b1ab9beb34798b2108de003452";
+
+#[rustfmt::skip]
+static EXCLUDE_FILES: &[&str] = &[
+    // TODO: CStr literals: c"…", cr"…"
+    // https://github.com/dtolnay/syn/issues/1502
+    "src/tools/clippy/tests/ui/needless_raw_string.rs",
+    "src/tools/clippy/tests/ui/needless_raw_string_hashes.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0085_expr_literals.rs",
+
+    // TODO: explicit tail calls: `become _g()`
+    // https://github.com/dtolnay/syn/issues/1501
+    "tests/ui/explicit-tail-calls/return-lifetime-sub.rs",
+
+    // TODO: non-lifetime binders: `where for<'a, T> &'a Struct<T>: Trait`
+    // https://github.com/dtolnay/syn/issues/1435
+    "src/tools/rustfmt/tests/source/issue_5721.rs",
+    "src/tools/rustfmt/tests/source/non-lifetime-binders.rs",
+    "src/tools/rustfmt/tests/target/issue_5721.rs",
+    "src/tools/rustfmt/tests/target/non-lifetime-binders.rs",
+    "tests/rustdoc-json/non_lifetime_binders.rs",
+    "tests/rustdoc/inline_cross/auxiliary/non_lifetime_binders.rs",
+    "tests/rustdoc/non_lifetime_binders.rs",
+
+    // TODO: return type notation: `where T: Trait<method(): Send>`
+    // https://github.com/dtolnay/syn/issues/1434
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0208_associated_return_type_bounds.rs",
+    "tests/ui/associated-type-bounds/return-type-notation/basic.rs",
+    "tests/ui/feature-gates/feature-gate-return_type_notation.rs",
+
+    // TODO: lazy type alias syntax with where-clause in trailing position
+    // https://github.com/dtolnay/syn/issues/1525
+    "tests/rustdoc/typedef-inner-variants-lazy_type_alias.rs",
+
+    // TODO: gen blocks and functions
+    // https://github.com/dtolnay/syn/issues/1526
+    "compiler/rustc_codegen_cranelift/example/gen_block_iterate.rs",
+    "tests/ui/coroutine/gen_block_is_iter.rs",
+    "tests/ui/coroutine/gen_block_iterate.rs",
+
+    // TODO: struct literal in match guard
+    // https://github.com/dtolnay/syn/issues/1527
+    "tests/ui/parser/struct-literal-in-match-guard.rs",
+
+    // Compile-fail expr parameter in const generic position: f::<1 + 2>()
+    "tests/ui/const-generics/early/closing-args-token.rs",
+    "tests/ui/const-generics/early/const-expression-parameter.rs",
+
+    // Compile-fail variadics in not the last position of a function parameter list
+    "tests/ui/parser/variadic-ffi-syntactic-pass.rs",
+
+    // Need at least one trait in impl Trait, no such type as impl 'static
+    "tests/ui/type-alias-impl-trait/generic_type_does_not_live_long_enough.rs",
+
+    // Negative polarity trait bound: `where T: !Copy`
+    "src/tools/rustfmt/tests/target/negative-bounds.rs",
+
+    // Lifetime bound inside for<>: `T: ~const ?for<'a: 'b> Trait<'a>`
+    "tests/ui/rfcs/rfc-2632-const-trait-impl/tilde-const-syntax.rs",
+
+    // Const impl that is not a trait impl: `impl ~const T {}`
+    "tests/ui/rfcs/rfc-2632-const-trait-impl/syntax.rs",
+
+    // Deprecated anonymous parameter syntax in traits
+    "src/tools/rustfmt/tests/source/trait.rs",
+    "src/tools/rustfmt/tests/target/trait.rs",
+    "tests/ui/issues/issue-13105.rs",
+    "tests/ui/issues/issue-13775.rs",
+    "tests/ui/issues/issue-34074.rs",
+    "tests/ui/proc-macro/trait-fn-args-2015.rs",
+
+    // Deprecated where-clause location
+    "src/tools/rustfmt/tests/source/issue_4257.rs",
+    "src/tools/rustfmt/tests/source/issue_4911.rs",
+    "src/tools/rustfmt/tests/target/issue_4257.rs",
+    "src/tools/rustfmt/tests/target/issue_4911.rs",
+    "tests/pretty/gat-bounds.rs",
+    "tests/rustdoc/generic-associated-types/gats.rs",
+
+    // Deprecated trait object syntax with parenthesized generic arguments and no dyn keyword
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0004_value_parameters_no_patterns.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0104_path_fn_trait_args.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0202_typepathfn_with_coloncolon.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0209_bare_dyn_types_with_paren_as_generic_args.rs",
+    "src/tools/rustfmt/tests/source/attrib.rs",
+    "src/tools/rustfmt/tests/source/closure.rs",
+    "src/tools/rustfmt/tests/source/existential_type.rs",
+    "src/tools/rustfmt/tests/source/fn-simple.rs",
+    "src/tools/rustfmt/tests/source/fn_args_layout-vertical.rs",
+    "src/tools/rustfmt/tests/source/issue-4689/one.rs",
+    "src/tools/rustfmt/tests/source/issue-4689/two.rs",
+    "src/tools/rustfmt/tests/source/paths.rs",
+    "src/tools/rustfmt/tests/source/structs.rs",
+    "src/tools/rustfmt/tests/target/attrib.rs",
+    "src/tools/rustfmt/tests/target/closure.rs",
+    "src/tools/rustfmt/tests/target/existential_type.rs",
+    "src/tools/rustfmt/tests/target/fn-simple.rs",
+    "src/tools/rustfmt/tests/target/fn.rs",
+    "src/tools/rustfmt/tests/target/fn_args_layout-vertical.rs",
+    "src/tools/rustfmt/tests/target/issue-4689/one.rs",
+    "src/tools/rustfmt/tests/target/issue-4689/two.rs",
+    "src/tools/rustfmt/tests/target/paths.rs",
+    "src/tools/rustfmt/tests/target/structs.rs",
+    "tests/codegen-units/item-collection/non-generic-closures.rs",
+    "tests/debuginfo/recursive-enum.rs",
+    "tests/pretty/closure-reform-pretty.rs",
+    "tests/run-make/reproducible-build-2/reproducible-build.rs",
+    "tests/run-make/reproducible-build/reproducible-build.rs",
+    "tests/ui/auxiliary/typeid-intrinsic-aux1.rs",
+    "tests/ui/auxiliary/typeid-intrinsic-aux2.rs",
+    "tests/ui/impl-trait/generic-with-implicit-hrtb-without-dyn.rs",
+    "tests/ui/lifetimes/auxiliary/lifetime_bound_will_change_warning_lib.rs",
+    "tests/ui/lifetimes/bare-trait-object-borrowck.rs",
+    "tests/ui/lifetimes/bare-trait-object.rs",
+    "tests/ui/parser/bounds-obj-parens.rs",
+
+    // Invalid unparenthesized range pattern inside slice pattern: `[1..]`
+    "tests/ui/consts/miri_unleashed/const_refers_to_static_cross_crate.rs",
+
+    // Various extensions to Rust syntax made up by rust-analyzer
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0012_type_item_where_clause.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0058_range_pat.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0123_param_list_vararg.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0131_existential_type.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0156_fn_def_param.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0179_use_tree_abs_star.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0188_const_param_default_path.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/ok/0015_use_tree.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/ok/0029_range_forms.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/ok/0051_parameter_attrs.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/ok/0055_dot_dot_dot.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/ok/0068_item_modifiers.rs",
+    "src/tools/rust-analyzer/crates/syntax/test_data/parser/validation/0031_block_inner_attrs.rs",
+    "src/tools/rust-analyzer/crates/syntax/test_data/parser/validation/0038_endless_inclusive_range.rs",
+    "src/tools/rust-analyzer/crates/syntax/test_data/parser/validation/0045_ambiguous_trait_object.rs",
+    "src/tools/rust-analyzer/crates/syntax/test_data/parser/validation/0046_mutable_const_item.rs",
+
+    // Placeholder syntax for "throw expressions"
+    "compiler/rustc_errors/src/translation.rs",
+    "src/tools/clippy/tests/ui/needless_return.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0204_yeet_expr.rs",
+    "tests/pretty/yeet-expr.rs",
+    "tests/ui/try-trait/yeet-for-option.rs",
+    "tests/ui/try-trait/yeet-for-result.rs",
+
+    // Edition 2015 code using identifiers that are now keywords
+    // TODO: some of these we should probably parse
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0159_try_macro_fallback.rs",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0160_try_macro_rules.rs",
+    "src/tools/rustfmt/tests/source/configs/indent_style/block_call.rs",
+    "src/tools/rustfmt/tests/source/configs/use_try_shorthand/false.rs",
+    "src/tools/rustfmt/tests/source/configs/use_try_shorthand/true.rs",
+    "src/tools/rustfmt/tests/source/issue_1306.rs",
+    "src/tools/rustfmt/tests/source/try-conversion.rs",
+    "src/tools/rustfmt/tests/target/configs/indent_style/block_call.rs",
+    "src/tools/rustfmt/tests/target/configs/use_try_shorthand/false.rs",
+    "src/tools/rustfmt/tests/target/issue-1681.rs",
+    "src/tools/rustfmt/tests/target/issue_1306.rs",
+    "tests/ui/dyn-keyword/dyn-2015-no-warnings-without-lints.rs",
+    "tests/ui/editions/edition-keywords-2015-2015.rs",
+    "tests/ui/editions/edition-keywords-2015-2018.rs",
+    "tests/ui/lint/lint_pre_expansion_extern_module_aux.rs",
+    "tests/ui/macros/macro-comma-support-rpass.rs",
+    "tests/ui/macros/try-macro.rs",
+    "tests/ui/parser/extern-crate-async.rs",
+    "tests/ui/try-block/try-is-identifier-edition2015.rs",
+
+    // Excessive nesting
+    "tests/ui/issues/issue-74564-if-expr-stack-overflow.rs",
+
+    // Testing tools on invalid syntax
+    "src/tools/rustfmt/tests/coverage/target/comments.rs",
+    "src/tools/rustfmt/tests/parser/issue-4126/invalid.rs",
+    "src/tools/rustfmt/tests/parser/issue_4418.rs",
+    "src/tools/rustfmt/tests/parser/unclosed-delims/issue_4466.rs",
+    "src/tools/rustfmt/tests/source/configs/disable_all_formatting/true.rs",
+    "src/tools/rustfmt/tests/source/configs/spaces_around_ranges/false.rs",
+    "src/tools/rustfmt/tests/source/configs/spaces_around_ranges/true.rs",
+    "src/tools/rustfmt/tests/source/type.rs",
+    "src/tools/rustfmt/tests/target/configs/spaces_around_ranges/false.rs",
+    "src/tools/rustfmt/tests/target/configs/spaces_around_ranges/true.rs",
+    "src/tools/rustfmt/tests/target/type.rs",
+    "tests/run-make/translation/test.rs",
+    "tests/ui/generics/issue-94432-garbage-ice.rs",
+
+    // Generated file containing a top-level expression, used with `include!`
+    "compiler/rustc_codegen_gcc/src/intrinsic/archs.rs",
+
+    // Clippy lint lists represented as expressions
+    "src/tools/clippy/clippy_lints/src/lib.deprecated.rs",
+
+    // Not actually test cases
+    "tests/ui/lint/expansion-time-include.rs",
+    "tests/ui/macros/auxiliary/macro-comma-support.rs",
+    "tests/ui/macros/auxiliary/macro-include-items-expr.rs",
+    "tests/ui/macros/include-single-expr-helper.rs",
+    "tests/ui/macros/include-single-expr-helper-1.rs",
+    "tests/ui/parser/issues/auxiliary/issue-21146-inc.rs",
+];
+
+#[rustfmt::skip]
+static EXCLUDE_DIRS: &[&str] = &[
+    // Inputs that intentionally do not parse
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/err",
+    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/err",
+
+    // Inputs that lex but do not necessarily parse
+    "src/tools/rust-analyzer/crates/parser/test_data/lexer",
+
+    // Inputs that used to crash rust-analyzer, but aren't necessarily supposed to parse
+    "src/tools/rust-analyzer/crates/syntax/test_data/parser/fuzz-failures",
+    "src/tools/rust-analyzer/crates/syntax/test_data/reparse/fuzz-failures",
+];
+
+// Directories in which a .stderr implies the corresponding .rs is not expected
+// to work.
+static UI_TEST_DIRS: &[&str] = &["tests/ui", "tests/rustdoc-ui"];
+
+pub fn for_each_rust_file(for_each: impl Fn(&Path) + Sync + Send) {
+    let mut rs_files = BTreeSet::new();
+
+    let repo_dir = Path::new("tests/rust");
+    for entry in WalkDir::new(repo_dir)
+        .into_iter()
+        .filter_entry(base_dir_filter)
+    {
+        let entry = entry.unwrap();
+        if !entry.file_type().is_dir() {
+            rs_files.insert(entry.into_path());
+        }
+    }
+
+    for ui_test_dir in UI_TEST_DIRS {
+        for entry in WalkDir::new(repo_dir.join(ui_test_dir)) {
+            let mut path = entry.unwrap().into_path();
+            if path.extension() == Some(OsStr::new("stderr")) {
+                loop {
+                    rs_files.remove(&path.with_extension("rs"));
+                    path = path.with_extension("");
+                    if path.extension().is_none() {
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    rs_files.par_iter().map(PathBuf::as_path).for_each(for_each);
+}
+
+pub fn base_dir_filter(entry: &DirEntry) -> bool {
+    let path = entry.path();
+
+    let mut path_string = path.to_string_lossy();
+    if cfg!(windows) {
+        path_string = path_string.replace('\\', "/").into();
+    }
+    let path_string = if path_string == "tests/rust" {
+        return true;
+    } else if let Some(path) = path_string.strip_prefix("tests/rust/") {
+        path
+    } else {
+        panic!("unexpected path in Rust dist: {}", path_string);
+    };
+
+    if path.is_dir() {
+        return !EXCLUDE_DIRS.contains(&path_string);
+    }
+
+    if path.extension() != Some(OsStr::new("rs")) {
+        return false;
+    }
+
+    !EXCLUDE_FILES.contains(&path_string)
+}
+
+#[allow(dead_code)]
+pub fn edition(path: &Path) -> &'static str {
+    if path.ends_with("dyn-2015-no-warnings-without-lints.rs") {
+        "2015"
+    } else {
+        "2018"
+    }
+}
+
+pub fn clone_rust() {
+    let needs_clone = match fs::read_to_string("tests/rust/COMMIT") {
+        Err(_) => true,
+        Ok(contents) => contents.trim() != REVISION,
+    };
+    if needs_clone {
+        download_and_unpack().unwrap();
+    }
+
+    let mut missing = String::new();
+    let test_src = Path::new("tests/rust");
+
+    let mut exclude_files_set = BTreeSet::new();
+    for exclude in EXCLUDE_FILES {
+        if !exclude_files_set.insert(exclude) {
+            panic!("duplicate path in EXCLUDE_FILES: {}", exclude);
+        }
+        for dir in EXCLUDE_DIRS {
+            if Path::new(exclude).starts_with(dir) {
+                panic!("excluded file {} is inside an excluded dir", exclude);
+            }
+        }
+        if !test_src.join(exclude).is_file() {
+            missing += "\ntests/rust/";
+            missing += exclude;
+        }
+    }
+
+    let mut exclude_dirs_set = BTreeSet::new();
+    for exclude in EXCLUDE_DIRS {
+        if !exclude_dirs_set.insert(exclude) {
+            panic!("duplicate path in EXCLUDE_DIRS: {}", exclude);
+        }
+        if !test_src.join(exclude).is_dir() {
+            missing += "\ntests/rust/";
+            missing += exclude;
+            missing += "/";
+        }
+    }
+
+    if !missing.is_empty() {
+        panic!("excluded test file does not exist:{}\n", missing);
+    }
+}
+
+fn download_and_unpack() -> Result<()> {
+    let url = format!(
+        "https://github.com/rust-lang/rust/archive/{}.tar.gz",
+        REVISION
+    );
+    let response = reqwest::blocking::get(url)?.error_for_status()?;
+    let progress = Progress::new(response);
+    let decoder = GzDecoder::new(progress);
+    let mut archive = Archive::new(decoder);
+    let prefix = format!("rust-{}", REVISION);
+
+    let tests_rust = Path::new("tests/rust");
+    if tests_rust.exists() {
+        fs::remove_dir_all(tests_rust)?;
+    }
+
+    for entry in archive.entries()? {
+        let mut entry = entry?;
+        let path = entry.path()?;
+        if path == Path::new("pax_global_header") {
+            continue;
+        }
+        let relative = path.strip_prefix(&prefix)?;
+        let out = tests_rust.join(relative);
+        entry.unpack(&out)?;
+    }
+
+    fs::write("tests/rust/COMMIT", REVISION)?;
+    Ok(())
+}
diff --git a/third_party/rust/syn/tests/repo/progress.rs b/third_party/rust/syn/tests/repo/progress.rs
new file mode 100644
index 0000000000..28c8a44b12
--- /dev/null
+++ b/third_party/rust/syn/tests/repo/progress.rs
@@ -0,0 +1,37 @@
+use std::io::{Read, Result};
+use std::time::{Duration, Instant};
+
+pub struct Progress<R> {
+    bytes: usize,
+    tick: Instant,
+    stream: R,
+}
+
+impl<R> Progress<R> {
+    pub fn new(stream: R) -> Self {
+        Progress {
+            bytes: 0,
+            tick: Instant::now() + Duration::from_millis(2000),
+            stream,
+        }
+    }
+}
+
+impl<R: Read> Read for Progress<R> {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
+        let num = self.stream.read(buf)?;
+        self.bytes += num;
+        let now = Instant::now();
+        if now > self.tick {
+            self.tick = now + Duration::from_millis(500);
+            errorf!("downloading... {} bytes\n", self.bytes);
+        }
+        Ok(num)
+    }
+}
+
+impl<R> Drop for Progress<R> {
+    fn drop(&mut self) {
+        errorf!("done ({} bytes)\n", self.bytes);
+    }
+}
diff --git a/third_party/rust/syn/tests/test_asyncness.rs b/third_party/rust/syn/tests/test_asyncness.rs
new file mode 100644
index 0000000000..9968934490
--- /dev/null
+++ b/third_party/rust/syn/tests/test_asyncness.rs
@@ -0,0 +1,43 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use syn::{Expr, Item};
+
+#[test]
+fn test_async_fn() {
+    let input = "async fn process() {}";
+
+    snapshot!(input as Item, @r###"
+    Item::Fn {
+        vis: Visibility::Inherited,
+        sig: Signature {
+            asyncness: Some,
+            ident: "process",
+            generics: Generics,
+            output: ReturnType::Default,
+        },
+        block: Block {
+            stmts: [],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_async_closure() {
+    let input = "async || {}";
+
+    snapshot!(input as Expr, @r###"
+    Expr::Closure {
+        asyncness: Some,
+        output: ReturnType::Default,
+        body: Expr::Block {
+            block: Block {
+                stmts: [],
+            },
+        },
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_attribute.rs b/third_party/rust/syn/tests/test_attribute.rs
new file mode 100644
index 0000000000..597ae3adc8
--- /dev/null
+++ b/third_party/rust/syn/tests/test_attribute.rs
@@ -0,0 +1,225 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use syn::parse::Parser;
+use syn::{Attribute, Meta};
+
+#[test]
+fn test_meta_item_word() {
+    let meta = test("#[foo]");
+
+    snapshot!(meta, @r###"
+    Meta::Path {
+        segments: [
+            PathSegment {
+                ident: "foo",
+            },
+        ],
+    }
+    "###);
+}
+
+#[test]
+fn test_meta_item_name_value() {
+    let meta = test("#[foo = 5]");
+
+    snapshot!(meta, @r###"
+    Meta::NameValue {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        value: Expr::Lit {
+            lit: 5,
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_meta_item_bool_value() {
+    let meta = test("#[foo = true]");
+
+    snapshot!(meta, @r###"
+    Meta::NameValue {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        value: Expr::Lit {
+            lit: Lit::Bool {
+                value: true,
+            },
+        },
+    }
+    "###);
+
+    let meta = test("#[foo = false]");
+
+    snapshot!(meta, @r###"
+    Meta::NameValue {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        value: Expr::Lit {
+            lit: Lit::Bool {
+                value: false,
+            },
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_meta_item_list_lit() {
+    let meta = test("#[foo(5)]");
+
+    snapshot!(meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`5`),
+    }
+    "###);
+}
+
+#[test]
+fn test_meta_item_list_word() {
+    let meta = test("#[foo(bar)]");
+
+    snapshot!(meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`bar`),
+    }
+    "###);
+}
+
+#[test]
+fn test_meta_item_list_name_value() {
+    let meta = test("#[foo(bar = 5)]");
+
+    snapshot!(meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`bar = 5`),
+    }
+    "###);
+}
+
+#[test]
+fn test_meta_item_list_bool_value() {
+    let meta = test("#[foo(bar = true)]");
+
+    snapshot!(meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`bar = true`),
+    }
+    "###);
+}
+
+#[test]
+fn test_meta_item_multiple() {
+    let meta = test("#[foo(word, name = 5, list(name2 = 6), word2)]");
+
+    snapshot!(meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`word , name = 5 , list (name2 = 6) , word2`),
+    }
+    "###);
+}
+
+#[test]
+fn test_bool_lit() {
+    let meta = test("#[foo(true)]");
+
+    snapshot!(meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`true`),
+    }
+    "###);
+}
+
+#[test]
+fn test_negative_lit() {
+    let meta = test("#[form(min = -1, max = 200)]");
+
+    snapshot!(meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "form",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`min = - 1 , max = 200`),
+    }
+    "###);
+}
+
+fn test(input: &str) -> Meta {
+    let attrs = Attribute::parse_outer.parse_str(input).unwrap();
+
+    assert_eq!(attrs.len(), 1);
+    let attr = attrs.into_iter().next().unwrap();
+
+    attr.meta
+}
diff --git a/third_party/rust/syn/tests/test_derive_input.rs b/third_party/rust/syn/tests/test_derive_input.rs
new file mode 100644
index 0000000000..c3d31eb0e9
--- /dev/null
+++ b/third_party/rust/syn/tests/test_derive_input.rs
@@ -0,0 +1,781 @@
+#![allow(
+    clippy::assertions_on_result_states,
+    clippy::manual_let_else,
+    clippy::too_many_lines,
+    clippy::uninlined_format_args
+)]
+
+#[macro_use]
+mod macros;
+
+use quote::quote;
+use syn::{Data, DeriveInput};
+
+#[test]
+fn test_unit() {
+    let input = quote! {
+        struct Unit;
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Inherited,
+        ident: "Unit",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unit,
+            semi_token: Some,
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_struct() {
+    let input = quote! {
+        #[derive(Debug, Clone)]
+        pub struct Item {
+            pub ident: Ident,
+            pub attrs: Vec<Attribute>
+        }
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        attrs: [
+            Attribute {
+                style: AttrStyle::Outer,
+                meta: Meta::List {
+                    path: Path {
+                        segments: [
+                            PathSegment {
+                                ident: "derive",
+                            },
+                        ],
+                    },
+                    delimiter: MacroDelimiter::Paren,
+                    tokens: TokenStream(`Debug , Clone`),
+                },
+            },
+        ],
+        vis: Visibility::Public,
+        ident: "Item",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Named {
+                named: [
+                    Field {
+                        vis: Visibility::Public,
+                        ident: Some("ident"),
+                        colon_token: Some,
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "Ident",
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                    Token![,],
+                    Field {
+                        vis: Visibility::Public,
+                        ident: Some("attrs"),
+                        colon_token: Some,
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "Vec",
+                                        arguments: PathArguments::AngleBracketed {
+                                            args: [
+                                                GenericArgument::Type(Type::Path {
+                                                    path: Path {
+                                                        segments: [
+                                                            PathSegment {
+                                                                ident: "Attribute",
+                                                            },
+                                                        ],
+                                                    },
+                                                }),
+                                            ],
+                                        },
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                ],
+            },
+        },
+    }
+    "###);
+
+    snapshot!(&input.attrs[0].meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "derive",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`Debug , Clone`),
+    }
+    "###);
+}
+
+#[test]
+fn test_union() {
+    let input = quote! {
+        union MaybeUninit<T> {
+            uninit: (),
+            value: T
+        }
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Inherited,
+        ident: "MaybeUninit",
+        generics: Generics {
+            lt_token: Some,
+            params: [
+                GenericParam::Type(TypeParam {
+                    ident: "T",
+                }),
+            ],
+            gt_token: Some,
+        },
+        data: Data::Union {
+            fields: FieldsNamed {
+                named: [
+                    Field {
+                        vis: Visibility::Inherited,
+                        ident: Some("uninit"),
+                        colon_token: Some,
+                        ty: Type::Tuple,
+                    },
+                    Token![,],
+                    Field {
+                        vis: Visibility::Inherited,
+                        ident: Some("value"),
+                        colon_token: Some,
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "T",
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                ],
+            },
+        },
+    }
+    "###);
+}
+
+#[test]
+#[cfg(feature = "full")]
+fn test_enum() {
+    let input = quote! {
+        /// See the std::result module documentation for details.
+        #[must_use]
+        pub enum Result<T, E> {
+            Ok(T),
+            Err(E),
+            Surprise = 0isize,
+
+            // Smuggling data into a proc_macro_derive,
+            // in the style of https://github.com/dtolnay/proc-macro-hack
+            ProcMacroHack = (0, "data").0
+        }
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        attrs: [
+            Attribute {
+                style: AttrStyle::Outer,
+                meta: Meta::NameValue {
+                    path: Path {
+                        segments: [
+                            PathSegment {
+                                ident: "doc",
+                            },
+                        ],
+                    },
+                    value: Expr::Lit {
+                        lit: " See the std::result module documentation for details.",
+                    },
+                },
+            },
+            Attribute {
+                style: AttrStyle::Outer,
+                meta: Meta::Path {
+                    segments: [
+                        PathSegment {
+                            ident: "must_use",
+                        },
+                    ],
+                },
+            },
+        ],
+        vis: Visibility::Public,
+        ident: "Result",
+        generics: Generics {
+            lt_token: Some,
+            params: [
+                GenericParam::Type(TypeParam {
+                    ident: "T",
+                }),
+                Token![,],
+                GenericParam::Type(TypeParam {
+                    ident: "E",
+                }),
+            ],
+            gt_token: Some,
+        },
+        data: Data::Enum {
+            variants: [
+                Variant {
+                    ident: "Ok",
+                    fields: Fields::Unnamed {
+                        unnamed: [
+                            Field {
+                                vis: Visibility::Inherited,
+                                ty: Type::Path {
+                                    path: Path {
+                                        segments: [
+                                            PathSegment {
+                                                ident: "T",
+                                            },
+                                        ],
+                                    },
+                                },
+                            },
+                        ],
+                    },
+                },
+                Token![,],
+                Variant {
+                    ident: "Err",
+                    fields: Fields::Unnamed {
+                        unnamed: [
+                            Field {
+                                vis: Visibility::Inherited,
+                                ty: Type::Path {
+                                    path: Path {
+                                        segments: [
+                                            PathSegment {
+                                                ident: "E",
+                                            },
+                                        ],
+                                    },
+                                },
+                            },
+                        ],
+                    },
+                },
+                Token![,],
+                Variant {
+                    ident: "Surprise",
+                    fields: Fields::Unit,
+                    discriminant: Some(Expr::Lit {
+                        lit: 0isize,
+                    }),
+                },
+                Token![,],
+                Variant {
+                    ident: "ProcMacroHack",
+                    fields: Fields::Unit,
+                    discriminant: Some(Expr::Field {
+                        base: Expr::Tuple {
+                            elems: [
+                                Expr::Lit {
+                                    lit: 0,
+                                },
+                                Token![,],
+                                Expr::Lit {
+                                    lit: "data",
+                                },
+                            ],
+                        },
+                        member: Member::Unnamed(Index {
+                            index: 0,
+                        }),
+                    }),
+                },
+            ],
+        },
+    }
+    "###);
+
+    let meta_items: Vec<_> = input.attrs.into_iter().map(|attr| attr.meta).collect();
+
+    snapshot!(meta_items, @r###"
+    [
+        Meta::NameValue {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "doc",
+                    },
+                ],
+            },
+            value: Expr::Lit {
+                lit: " See the std::result module documentation for details.",
+            },
+        },
+        Meta::Path {
+            segments: [
+                PathSegment {
+                    ident: "must_use",
+                },
+            ],
+        },
+    ]
+    "###);
+}
+
+#[test]
+fn test_attr_with_non_mod_style_path() {
+    let input = quote! {
+        #[inert <T>]
+        struct S;
+    };
+
+    syn::parse2::<DeriveInput>(input).unwrap_err();
+}
+
+#[test]
+fn test_attr_with_mod_style_path_with_self() {
+    let input = quote! {
+        #[foo::self]
+        struct S;
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        attrs: [
+            Attribute {
+                style: AttrStyle::Outer,
+                meta: Meta::Path {
+                    segments: [
+                        PathSegment {
+                            ident: "foo",
+                        },
+                        Token![::],
+                        PathSegment {
+                            ident: "self",
+                        },
+                    ],
+                },
+            },
+        ],
+        vis: Visibility::Inherited,
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unit,
+            semi_token: Some,
+        },
+    }
+    "###);
+
+    snapshot!(&input.attrs[0].meta, @r###"
+    Meta::Path {
+        segments: [
+            PathSegment {
+                ident: "foo",
+            },
+            Token![::],
+            PathSegment {
+                ident: "self",
+            },
+        ],
+    }
+    "###);
+}
+
+#[test]
+fn test_pub_restricted() {
+    // Taken from tests/rust/src/test/ui/resolve/auxiliary/privacy-struct-ctor.rs
+    let input = quote! {
+        pub(in m) struct Z(pub(in m::n) u8);
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Restricted {
+            in_token: Some,
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "m",
+                    },
+                ],
+            },
+        },
+        ident: "Z",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unnamed {
+                unnamed: [
+                    Field {
+                        vis: Visibility::Restricted {
+                            in_token: Some,
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "m",
+                                    },
+                                    Token![::],
+                                    PathSegment {
+                                        ident: "n",
+                                    },
+                                ],
+                            },
+                        },
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "u8",
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                ],
+            },
+            semi_token: Some,
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_pub_restricted_crate() {
+    let input = quote! {
+        pub(crate) struct S;
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Restricted {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "crate",
+                    },
+                ],
+            },
+        },
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unit,
+            semi_token: Some,
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_pub_restricted_super() {
+    let input = quote! {
+        pub(super) struct S;
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Restricted {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "super",
+                    },
+                ],
+            },
+        },
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unit,
+            semi_token: Some,
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_pub_restricted_in_super() {
+    let input = quote! {
+        pub(in super) struct S;
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Restricted {
+            in_token: Some,
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "super",
+                    },
+                ],
+            },
+        },
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unit,
+            semi_token: Some,
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_fields_on_unit_struct() {
+    let input = quote! {
+        struct S;
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Inherited,
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unit,
+            semi_token: Some,
+        },
+    }
+    "###);
+
+    let data = match input.data {
+        Data::Struct(data) => data,
+        _ => panic!("expected a struct"),
+    };
+
+    assert_eq!(0, data.fields.iter().count());
+}
+
+#[test]
+fn test_fields_on_named_struct() {
+    let input = quote! {
+        struct S {
+            foo: i32,
+            pub bar: String,
+        }
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Inherited,
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Named {
+                named: [
+                    Field {
+                        vis: Visibility::Inherited,
+                        ident: Some("foo"),
+                        colon_token: Some,
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "i32",
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                    Token![,],
+                    Field {
+                        vis: Visibility::Public,
+                        ident: Some("bar"),
+                        colon_token: Some,
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "String",
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                    Token![,],
+                ],
+            },
+        },
+    }
+    "###);
+
+    let data = match input.data {
+        Data::Struct(data) => data,
+        _ => panic!("expected a struct"),
+    };
+
+    snapshot!(data.fields.into_iter().collect::<Vec<_>>(), @r###"
+    [
+        Field {
+            vis: Visibility::Inherited,
+            ident: Some("foo"),
+            colon_token: Some,
+            ty: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "i32",
+                        },
+                    ],
+                },
+            },
+        },
+        Field {
+            vis: Visibility::Public,
+            ident: Some("bar"),
+            colon_token: Some,
+            ty: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "String",
+                        },
+                    ],
+                },
+            },
+        },
+    ]
+    "###);
+}
+
+#[test]
+fn test_fields_on_tuple_struct() {
+    let input = quote! {
+        struct S(i32, pub String);
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Inherited,
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unnamed {
+                unnamed: [
+                    Field {
+                        vis: Visibility::Inherited,
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "i32",
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                    Token![,],
+                    Field {
+                        vis: Visibility::Public,
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "String",
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                ],
+            },
+            semi_token: Some,
+        },
+    }
+    "###);
+
+    let data = match input.data {
+        Data::Struct(data) => data,
+        _ => panic!("expected a struct"),
+    };
+
+    snapshot!(data.fields.iter().collect::<Vec<_>>(), @r###"
+    [
+        Field {
+            vis: Visibility::Inherited,
+            ty: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "i32",
+                        },
+                    ],
+                },
+            },
+        },
+        Field {
+            vis: Visibility::Public,
+            ty: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "String",
+                        },
+                    ],
+                },
+            },
+        },
+    ]
+    "###);
+}
+
+#[test]
+fn test_ambiguous_crate() {
+    let input = quote! {
+        // The field type is `(crate::X)` not `crate (::X)`.
+        struct S(crate::X);
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Inherited,
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Unnamed {
+                unnamed: [
+                    Field {
+                        vis: Visibility::Inherited,
+                        ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "crate",
+                                    },
+                                    Token![::],
+                                    PathSegment {
+                                        ident: "X",
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                ],
+            },
+            semi_token: Some,
+        },
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_expr.rs b/third_party/rust/syn/tests/test_expr.rs
new file mode 100644
index 0000000000..daf0d63c3b
--- /dev/null
+++ b/third_party/rust/syn/tests/test_expr.rs
@@ -0,0 +1,540 @@
+#![allow(clippy::single_element_loop, clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group};
+use quote::{quote, ToTokens as _};
+use syn::punctuated::Punctuated;
+use syn::{parse_quote, token, Expr, ExprRange, ExprTuple, Stmt, Token};
+
+#[test]
+fn test_expr_parse() {
+    let tokens = quote!(..100u32);
+    snapshot!(tokens as Expr, @r###"
+    Expr::Range {
+        limits: RangeLimits::HalfOpen,
+        end: Some(Expr::Lit {
+            lit: 100u32,
+        }),
+    }
+    "###);
+
+    let tokens = quote!(..100u32);
+    snapshot!(tokens as ExprRange, @r###"
+    ExprRange {
+        limits: RangeLimits::HalfOpen,
+        end: Some(Expr::Lit {
+            lit: 100u32,
+        }),
+    }
+    "###);
+}
+
+#[test]
+fn test_await() {
+    // Must not parse as Expr::Field.
+    let tokens = quote!(fut.await);
+
+    snapshot!(tokens as Expr, @r###"
+    Expr::Await {
+        base: Expr::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "fut",
+                    },
+                ],
+            },
+        },
+    }
+    "###);
+}
+
+#[rustfmt::skip]
+#[test]
+fn test_tuple_multi_index() {
+    let expected = snapshot!("tuple.0.0" as Expr, @r###"
+    Expr::Field {
+        base: Expr::Field {
+            base: Expr::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "tuple",
+                        },
+                    ],
+                },
+            },
+            member: Member::Unnamed(Index {
+                index: 0,
+            }),
+        },
+        member: Member::Unnamed(Index {
+            index: 0,
+        }),
+    }
+    "###);
+
+    for &input in &[
+        "tuple .0.0",
+        "tuple. 0.0",
+        "tuple.0 .0",
+        "tuple.0. 0",
+        "tuple . 0 . 0",
+    ] {
+        assert_eq!(expected, syn::parse_str(input).unwrap());
+    }
+
+    for tokens in [
+        quote!(tuple.0.0),
+        quote!(tuple .0.0),
+        quote!(tuple. 0.0),
+        quote!(tuple.0 .0),
+        quote!(tuple.0. 0),
+        quote!(tuple . 0 . 0),
+    ] {
+        assert_eq!(expected, syn::parse2(tokens).unwrap());
+    }
+}
+
+#[test]
+fn test_macro_variable_func() {
+    // mimics the token stream corresponding to `$fn()`
+    let path = Group::new(Delimiter::None, quote!(f));
+    let tokens = quote!(#path());
+
+    snapshot!(tokens as Expr, @r###"
+    Expr::Call {
+        func: Expr::Group {
+            expr: Expr::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "f",
+                        },
+                    ],
+                },
+            },
+        },
+    }
+    "###);
+
+    let path = Group::new(Delimiter::None, quote! { #[inside] f });
+    let tokens = quote!(#[outside] #path());
+
+    snapshot!(tokens as Expr, @r###"
+    Expr::Call {
+        attrs: [
+            Attribute {
+                style: AttrStyle::Outer,
+                meta: Meta::Path {
+                    segments: [
+                        PathSegment {
+                            ident: "outside",
+                        },
+                    ],
+                },
+            },
+        ],
+        func: Expr::Group {
+            expr: Expr::Path {
+                attrs: [
+                    Attribute {
+                        style: AttrStyle::Outer,
+                        meta: Meta::Path {
+                            segments: [
+                                PathSegment {
+                                    ident: "inside",
+                                },
+                            ],
+                        },
+                    },
+                ],
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "f",
+                        },
+                    ],
+                },
+            },
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_macro_variable_macro() {
+    // mimics the token stream corresponding to `$macro!()`
+    let mac = Group::new(Delimiter::None, quote!(m));
+    let tokens = quote!(#mac!());
+
+    snapshot!(tokens as Expr, @r###"
+    Expr::Macro {
+        mac: Macro {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "m",
+                    },
+                ],
+            },
+            delimiter: MacroDelimiter::Paren,
+            tokens: TokenStream(``),
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_macro_variable_struct() {
+    // mimics the token stream corresponding to `$struct {}`
+    let s = Group::new(Delimiter::None, quote! { S });
+    let tokens = quote!(#s {});
+
+    snapshot!(tokens as Expr, @r###"
+    Expr::Struct {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "S",
+                },
+            ],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_macro_variable_unary() {
+    // mimics the token stream corresponding to `$expr.method()` where expr is `&self`
+    let inner = Group::new(Delimiter::None, quote!(&self));
+    let tokens = quote!(#inner.method());
+    snapshot!(tokens as Expr, @r###"
+    Expr::MethodCall {
+        receiver: Expr::Group {
+            expr: Expr::Reference {
+                expr: Expr::Path {
+                    path: Path {
+                        segments: [
+                            PathSegment {
+                                ident: "self",
+                            },
+                        ],
+                    },
+                },
+            },
+        },
+        method: "method",
+    }
+    "###);
+}
+
+#[test]
+fn test_macro_variable_match_arm() {
+    // mimics the token stream corresponding to `match v { _ => $expr }`
+    let expr = Group::new(Delimiter::None, quote! { #[a] () });
+    let tokens = quote!(match v { _ => #expr });
+    snapshot!(tokens as Expr, @r###"
+    Expr::Match {
+        expr: Expr::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "v",
+                    },
+                ],
+            },
+        },
+        arms: [
+            Arm {
+                pat: Pat::Wild,
+                body: Expr::Group {
+                    expr: Expr::Tuple {
+                        attrs: [
+                            Attribute {
+                                style: AttrStyle::Outer,
+                                meta: Meta::Path {
+                                    segments: [
+                                        PathSegment {
+                                            ident: "a",
+                                        },
+                                    ],
+                                },
+                            },
+                        ],
+                    },
+                },
+            },
+        ],
+    }
+    "###);
+
+    let expr = Group::new(Delimiter::None, quote!(loop {} + 1));
+    let tokens = quote!(match v { _ => #expr });
+    snapshot!(tokens as Expr, @r###"
+    Expr::Match {
+        expr: Expr::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "v",
+                    },
+                ],
+            },
+        },
+        arms: [
+            Arm {
+                pat: Pat::Wild,
+                body: Expr::Group {
+                    expr: Expr::Binary {
+                        left: Expr::Loop {
+                            body: Block {
+                                stmts: [],
+                            },
+                        },
+                        op: BinOp::Add,
+                        right: Expr::Lit {
+                            lit: 1,
+                        },
+                    },
+                },
+            },
+        ],
+    }
+    "###);
+}
+
+// https://github.com/dtolnay/syn/issues/1019
+#[test]
+fn test_closure_vs_rangefull() {
+    #[rustfmt::skip] // rustfmt bug: https://github.com/rust-lang/rustfmt/issues/4808
+    let tokens = quote!(|| .. .method());
+    snapshot!(tokens as Expr, @r###"
+    Expr::MethodCall {
+        receiver: Expr::Closure {
+            output: ReturnType::Default,
+            body: Expr::Range {
+                limits: RangeLimits::HalfOpen,
+            },
+        },
+        method: "method",
+    }
+    "###);
+}
+
+#[test]
+fn test_postfix_operator_after_cast() {
+    syn::parse_str::<Expr>("|| &x as T[0]").unwrap_err();
+    syn::parse_str::<Expr>("|| () as ()()").unwrap_err();
+}
+
+#[test]
+fn test_ranges() {
+    syn::parse_str::<Expr>("..").unwrap();
+    syn::parse_str::<Expr>("..hi").unwrap();
+    syn::parse_str::<Expr>("lo..").unwrap();
+    syn::parse_str::<Expr>("lo..hi").unwrap();
+
+    syn::parse_str::<Expr>("..=").unwrap_err();
+    syn::parse_str::<Expr>("..=hi").unwrap();
+    syn::parse_str::<Expr>("lo..=").unwrap_err();
+    syn::parse_str::<Expr>("lo..=hi").unwrap();
+
+    syn::parse_str::<Expr>("...").unwrap_err();
+    syn::parse_str::<Expr>("...hi").unwrap_err();
+    syn::parse_str::<Expr>("lo...").unwrap_err();
+    syn::parse_str::<Expr>("lo...hi").unwrap_err();
+}
+
+#[test]
+fn test_ambiguous_label() {
+    for stmt in [
+        quote! {
+            return 'label: loop { break 'label 42; };
+        },
+        quote! {
+            break ('label: loop { break 'label 42; });
+        },
+        quote! {
+            break 1 + 'label: loop { break 'label 42; };
+        },
+        quote! {
+            break 'outer 'inner: loop { break 'inner 42; };
+        },
+    ] {
+        syn::parse2::<Stmt>(stmt).unwrap();
+    }
+
+    for stmt in [
+        // Parentheses required. See https://github.com/rust-lang/rust/pull/87026.
+        quote! {
+            break 'label: loop { break 'label 42; };
+        },
+    ] {
+        syn::parse2::<Stmt>(stmt).unwrap_err();
+    }
+}
+
+#[test]
+fn test_extended_interpolated_path() {
+    let path = Group::new(Delimiter::None, quote!(a::b));
+
+    let tokens = quote!(if #path {});
+    snapshot!(tokens as Expr, @r###"
+    Expr::If {
+        cond: Expr::Group {
+            expr: Expr::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "a",
+                        },
+                        Token![::],
+                        PathSegment {
+                            ident: "b",
+                        },
+                    ],
+                },
+            },
+        },
+        then_branch: Block {
+            stmts: [],
+        },
+    }
+    "###);
+
+    let tokens = quote!(#path {});
+    snapshot!(tokens as Expr, @r###"
+    Expr::Struct {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "a",
+                },
+                Token![::],
+                PathSegment {
+                    ident: "b",
+                },
+            ],
+        },
+    }
+    "###);
+
+    let tokens = quote!(#path :: c);
+    snapshot!(tokens as Expr, @r###"
+    Expr::Path {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "a",
+                },
+                Token![::],
+                PathSegment {
+                    ident: "b",
+                },
+                Token![::],
+                PathSegment {
+                    ident: "c",
+                },
+            ],
+        },
+    }
+    "###);
+
+    let nested = Group::new(Delimiter::None, quote!(a::b || true));
+    let tokens = quote!(if #nested && false {});
+    snapshot!(tokens as Expr, @r###"
+    Expr::If {
+        cond: Expr::Binary {
+            left: Expr::Group {
+                expr: Expr::Binary {
+                    left: Expr::Path {
+                        path: Path {
+                            segments: [
+                                PathSegment {
+                                    ident: "a",
+                                },
+                                Token![::],
+                                PathSegment {
+                                    ident: "b",
+                                },
+                            ],
+                        },
+                    },
+                    op: BinOp::Or,
+                    right: Expr::Lit {
+                        lit: Lit::Bool {
+                            value: true,
+                        },
+                    },
+                },
+            },
+            op: BinOp::And,
+            right: Expr::Lit {
+                lit: Lit::Bool {
+                    value: false,
+                },
+            },
+        },
+        then_branch: Block {
+            stmts: [],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_tuple_comma() {
+    let mut expr = ExprTuple {
+        attrs: Vec::new(),
+        paren_token: token::Paren::default(),
+        elems: Punctuated::new(),
+    };
+    snapshot!(expr.to_token_stream() as Expr, @"Expr::Tuple");
+
+    expr.elems.push_value(parse_quote!(continue));
+    // Must not parse to Expr::Paren
+    snapshot!(expr.to_token_stream() as Expr, @r###"
+    Expr::Tuple {
+        elems: [
+            Expr::Continue,
+            Token![,],
+        ],
+    }
+    "###);
+
+    expr.elems.push_punct(<Token![,]>::default());
+    snapshot!(expr.to_token_stream() as Expr, @r###"
+    Expr::Tuple {
+        elems: [
+            Expr::Continue,
+            Token![,],
+        ],
+    }
+    "###);
+
+    expr.elems.push_value(parse_quote!(continue));
+    snapshot!(expr.to_token_stream() as Expr, @r###"
+    Expr::Tuple {
+        elems: [
+            Expr::Continue,
+            Token![,],
+            Expr::Continue,
+        ],
+    }
+    "###);
+
+    expr.elems.push_punct(<Token![,]>::default());
+    snapshot!(expr.to_token_stream() as Expr, @r###"
+    Expr::Tuple {
+        elems: [
+            Expr::Continue,
+            Token![,],
+            Expr::Continue,
+            Token![,],
+        ],
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_generics.rs b/third_party/rust/syn/tests/test_generics.rs
new file mode 100644
index 0000000000..3faf0dba59
--- /dev/null
+++ b/third_party/rust/syn/tests/test_generics.rs
@@ -0,0 +1,282 @@
+#![allow(
+    clippy::manual_let_else,
+    clippy::too_many_lines,
+    clippy::uninlined_format_args
+)]
+
+#[macro_use]
+mod macros;
+
+use quote::quote;
+use syn::{DeriveInput, ItemFn, TypeParamBound, WhereClause, WherePredicate};
+
+#[test]
+fn test_split_for_impl() {
+    let input = quote! {
+        struct S<'a, 'b: 'a, #[may_dangle] T: 'a = ()> where T: Debug;
+    };
+
+    snapshot!(input as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Inherited,
+        ident: "S",
+        generics: Generics {
+            lt_token: Some,
+            params: [
+                GenericParam::Lifetime(LifetimeParam {
+                    lifetime: Lifetime {
+                        ident: "a",
+                    },
+                }),
+                Token![,],
+                GenericParam::Lifetime(LifetimeParam {
+                    lifetime: Lifetime {
+                        ident: "b",
+                    },
+                    colon_token: Some,
+                    bounds: [
+                        Lifetime {
+                            ident: "a",
+                        },
+                    ],
+                }),
+                Token![,],
+                GenericParam::Type(TypeParam {
+                    attrs: [
+                        Attribute {
+                            style: AttrStyle::Outer,
+                            meta: Meta::Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "may_dangle",
+                                    },
+                                ],
+                            },
+                        },
+                    ],
+                    ident: "T",
+                    colon_token: Some,
+                    bounds: [
+                        TypeParamBound::Lifetime {
+                            ident: "a",
+                        },
+                    ],
+                    eq_token: Some,
+                    default: Some(Type::Tuple),
+                }),
+            ],
+            gt_token: Some,
+            where_clause: Some(WhereClause {
+                predicates: [
+                    WherePredicate::Type(PredicateType {
+                        bounded_ty: Type::Path {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "T",
+                                    },
+                                ],
+                            },
+                        },
+                        bounds: [
+                            TypeParamBound::Trait(TraitBound {
+                                path: Path {
+                                    segments: [
+                                        PathSegment {
+                                            ident: "Debug",
+                                        },
+                                    ],
+                                },
+                            }),
+                        ],
+                    }),
+                ],
+            }),
+        },
+        data: Data::Struct {
+            fields: Fields::Unit,
+            semi_token: Some,
+        },
+    }
+    "###);
+
+    let generics = input.generics;
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    let generated = quote! {
+        impl #impl_generics MyTrait for Test #ty_generics #where_clause {}
+    };
+    let expected = quote! {
+        impl<'a, 'b: 'a, #[may_dangle] T: 'a> MyTrait
+        for Test<'a, 'b, T>
+        where
+            T: Debug
+        {}
+    };
+    assert_eq!(generated.to_string(), expected.to_string());
+
+    let turbofish = ty_generics.as_turbofish();
+    let generated = quote! {
+        Test #turbofish
+    };
+    let expected = quote! {
+        Test::<'a, 'b, T>
+    };
+    assert_eq!(generated.to_string(), expected.to_string());
+}
+
+#[test]
+fn test_ty_param_bound() {
+    let tokens = quote!('a);
+    snapshot!(tokens as TypeParamBound, @r###"
+    TypeParamBound::Lifetime {
+        ident: "a",
+    }
+    "###);
+
+    let tokens = quote!('_);
+    snapshot!(tokens as TypeParamBound, @r###"
+    TypeParamBound::Lifetime {
+        ident: "_",
+    }
+    "###);
+
+    let tokens = quote!(Debug);
+    snapshot!(tokens as TypeParamBound, @r###"
+    TypeParamBound::Trait(TraitBound {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "Debug",
+                },
+            ],
+        },
+    })
+    "###);
+
+    let tokens = quote!(?Sized);
+    snapshot!(tokens as TypeParamBound, @r###"
+    TypeParamBound::Trait(TraitBound {
+        modifier: TraitBoundModifier::Maybe,
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "Sized",
+                },
+            ],
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_fn_precedence_in_where_clause() {
+    // This should parse as two separate bounds, `FnOnce() -> i32` and `Send` - not
+    // `FnOnce() -> (i32 + Send)`.
+    let input = quote! {
+        fn f<G>()
+        where
+            G: FnOnce() -> i32 + Send,
+        {
+        }
+    };
+
+    snapshot!(input as ItemFn, @r###"
+    ItemFn {
+        vis: Visibility::Inherited,
+        sig: Signature {
+            ident: "f",
+            generics: Generics {
+                lt_token: Some,
+                params: [
+                    GenericParam::Type(TypeParam {
+                        ident: "G",
+                    }),
+                ],
+                gt_token: Some,
+                where_clause: Some(WhereClause {
+                    predicates: [
+                        WherePredicate::Type(PredicateType {
+                            bounded_ty: Type::Path {
+                                path: Path {
+                                    segments: [
+                                        PathSegment {
+                                            ident: "G",
+                                        },
+                                    ],
+                                },
+                            },
+                            bounds: [
+                                TypeParamBound::Trait(TraitBound {
+                                    path: Path {
+                                        segments: [
+                                            PathSegment {
+                                                ident: "FnOnce",
+                                                arguments: PathArguments::Parenthesized {
+                                                    output: ReturnType::Type(
+                                                        Type::Path {
+                                                            path: Path {
+                                                                segments: [
+                                                                    PathSegment {
+                                                                        ident: "i32",
+                                                                    },
+                                                                ],
+                                                            },
+                                                        },
+                                                    ),
+                                                },
+                                            },
+                                        ],
+                                    },
+                                }),
+                                Token![+],
+                                TypeParamBound::Trait(TraitBound {
+                                    path: Path {
+                                        segments: [
+                                            PathSegment {
+                                                ident: "Send",
+                                            },
+                                        ],
+                                    },
+                                }),
+                            ],
+                        }),
+                        Token![,],
+                    ],
+                }),
+            },
+            output: ReturnType::Default,
+        },
+        block: Block {
+            stmts: [],
+        },
+    }
+    "###);
+
+    let where_clause = input.sig.generics.where_clause.as_ref().unwrap();
+    assert_eq!(where_clause.predicates.len(), 1);
+
+    let predicate = match &where_clause.predicates[0] {
+        WherePredicate::Type(pred) => pred,
+        _ => panic!("wrong predicate kind"),
+    };
+
+    assert_eq!(predicate.bounds.len(), 2, "{:#?}", predicate.bounds);
+
+    let first_bound = &predicate.bounds[0];
+    assert_eq!(quote!(#first_bound).to_string(), "FnOnce () -> i32");
+
+    let second_bound = &predicate.bounds[1];
+    assert_eq!(quote!(#second_bound).to_string(), "Send");
+}
+
+#[test]
+fn test_where_clause_at_end_of_input() {
+    let input = quote! {
+        where
+    };
+
+    snapshot!(input as WhereClause, @"WhereClause");
+
+    assert_eq!(input.predicates.len(), 0);
+}
diff --git a/third_party/rust/syn/tests/test_grouping.rs b/third_party/rust/syn/tests/test_grouping.rs
new file mode 100644
index 0000000000..6a73a92442
--- /dev/null
+++ b/third_party/rust/syn/tests/test_grouping.rs
@@ -0,0 +1,53 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, Literal, Punct, Spacing, TokenStream, TokenTree};
+use syn::Expr;
+
+#[test]
+fn test_grouping() {
+    let tokens: TokenStream = TokenStream::from_iter(vec![
+        TokenTree::Literal(Literal::i32_suffixed(1)),
+        TokenTree::Punct(Punct::new('+', Spacing::Alone)),
+        TokenTree::Group(Group::new(
+            Delimiter::None,
+            TokenStream::from_iter(vec![
+                TokenTree::Literal(Literal::i32_suffixed(2)),
+                TokenTree::Punct(Punct::new('+', Spacing::Alone)),
+                TokenTree::Literal(Literal::i32_suffixed(3)),
+            ]),
+        )),
+        TokenTree::Punct(Punct::new('*', Spacing::Alone)),
+        TokenTree::Literal(Literal::i32_suffixed(4)),
+    ]);
+
+    assert_eq!(tokens.to_string(), "1i32 + 2i32 + 3i32 * 4i32");
+
+    snapshot!(tokens as Expr, @r###"
+    Expr::Binary {
+        left: Expr::Lit {
+            lit: 1i32,
+        },
+        op: BinOp::Add,
+        right: Expr::Binary {
+            left: Expr::Group {
+                expr: Expr::Binary {
+                    left: Expr::Lit {
+                        lit: 2i32,
+                    },
+                    op: BinOp::Add,
+                    right: Expr::Lit {
+                        lit: 3i32,
+                    },
+                },
+            },
+            op: BinOp::Mul,
+            right: Expr::Lit {
+                lit: 4i32,
+            },
+        },
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_ident.rs b/third_party/rust/syn/tests/test_ident.rs
new file mode 100644
index 0000000000..ee01bfcc9f
--- /dev/null
+++ b/third_party/rust/syn/tests/test_ident.rs
@@ -0,0 +1,85 @@
+use proc_macro2::{Ident, Span, TokenStream};
+use std::str::FromStr;
+use syn::Result;
+
+fn parse(s: &str) -> Result<Ident> {
+    syn::parse2(TokenStream::from_str(s).unwrap())
+}
+
+fn new(s: &str) -> Ident {
+    Ident::new(s, Span::call_site())
+}
+
+#[test]
+fn ident_parse() {
+    parse("String").unwrap();
+}
+
+#[test]
+fn ident_parse_keyword() {
+    parse("abstract").unwrap_err();
+}
+
+#[test]
+fn ident_parse_empty() {
+    parse("").unwrap_err();
+}
+
+#[test]
+fn ident_parse_lifetime() {
+    parse("'static").unwrap_err();
+}
+
+#[test]
+fn ident_parse_underscore() {
+    parse("_").unwrap_err();
+}
+
+#[test]
+fn ident_parse_number() {
+    parse("255").unwrap_err();
+}
+
+#[test]
+fn ident_parse_invalid() {
+    parse("a#").unwrap_err();
+}
+
+#[test]
+fn ident_new() {
+    new("String");
+}
+
+#[test]
+fn ident_new_keyword() {
+    new("abstract");
+}
+
+#[test]
+#[should_panic(expected = "use Option<Ident>")]
+fn ident_new_empty() {
+    new("");
+}
+
+#[test]
+#[should_panic(expected = "not a valid Ident")]
+fn ident_new_lifetime() {
+    new("'static");
+}
+
+#[test]
+fn ident_new_underscore() {
+    new("_");
+}
+
+#[test]
+#[should_panic(expected = "use Literal instead")]
+fn ident_new_number() {
+    new("255");
+}
+
+#[test]
+#[should_panic(expected = "\"a#\" is not a valid Ident")]
+fn ident_new_invalid() {
+    new("a#");
+}
diff --git a/third_party/rust/syn/tests/test_item.rs b/third_party/rust/syn/tests/test_item.rs
new file mode 100644
index 0000000000..db9e3ab515
--- /dev/null
+++ b/third_party/rust/syn/tests/test_item.rs
@@ -0,0 +1,332 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, Ident, Span, TokenStream, TokenTree};
+use quote::quote;
+use syn::{Item, ItemTrait};
+
+#[test]
+fn test_macro_variable_attr() {
+    // mimics the token stream corresponding to `$attr fn f() {}`
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Group(Group::new(Delimiter::None, quote! { #[test] })),
+        TokenTree::Ident(Ident::new("fn", Span::call_site())),
+        TokenTree::Ident(Ident::new("f", Span::call_site())),
+        TokenTree::Group(Group::new(Delimiter::Parenthesis, TokenStream::new())),
+        TokenTree::Group(Group::new(Delimiter::Brace, TokenStream::new())),
+    ]);
+
+    snapshot!(tokens as Item, @r###"
+    Item::Fn {
+        attrs: [
+            Attribute {
+                style: AttrStyle::Outer,
+                meta: Meta::Path {
+                    segments: [
+                        PathSegment {
+                            ident: "test",
+                        },
+                    ],
+                },
+            },
+        ],
+        vis: Visibility::Inherited,
+        sig: Signature {
+            ident: "f",
+            generics: Generics,
+            output: ReturnType::Default,
+        },
+        block: Block {
+            stmts: [],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_negative_impl() {
+    // Rustc parses all of the following.
+
+    #[cfg(any())]
+    impl ! {}
+    let tokens = quote! {
+        impl ! {}
+    };
+    snapshot!(tokens as Item, @r###"
+    Item::Impl {
+        generics: Generics,
+        self_ty: Type::Never,
+    }
+    "###);
+
+    #[cfg(any())]
+    #[rustfmt::skip]
+    impl !Trait {}
+    let tokens = quote! {
+        impl !Trait {}
+    };
+    snapshot!(tokens as Item, @r###"
+    Item::Impl {
+        generics: Generics,
+        self_ty: Type::Verbatim(`! Trait`),
+    }
+    "###);
+
+    #[cfg(any())]
+    impl !Trait for T {}
+    let tokens = quote! {
+        impl !Trait for T {}
+    };
+    snapshot!(tokens as Item, @r###"
+    Item::Impl {
+        generics: Generics,
+        trait_: Some((
+            Some,
+            Path {
+                segments: [
+                    PathSegment {
+                        ident: "Trait",
+                    },
+                ],
+            },
+        )),
+        self_ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "T",
+                    },
+                ],
+            },
+        },
+    }
+    "###);
+
+    #[cfg(any())]
+    #[rustfmt::skip]
+    impl !! {}
+    let tokens = quote! {
+        impl !! {}
+    };
+    snapshot!(tokens as Item, @r###"
+    Item::Impl {
+        generics: Generics,
+        self_ty: Type::Verbatim(`! !`),
+    }
+    "###);
+}
+
+#[test]
+fn test_macro_variable_impl() {
+    // mimics the token stream corresponding to `impl $trait for $ty {}`
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Ident(Ident::new("impl", Span::call_site())),
+        TokenTree::Group(Group::new(Delimiter::None, quote!(Trait))),
+        TokenTree::Ident(Ident::new("for", Span::call_site())),
+        TokenTree::Group(Group::new(Delimiter::None, quote!(Type))),
+        TokenTree::Group(Group::new(Delimiter::Brace, TokenStream::new())),
+    ]);
+
+    snapshot!(tokens as Item, @r###"
+    Item::Impl {
+        generics: Generics,
+        trait_: Some((
+            None,
+            Path {
+                segments: [
+                    PathSegment {
+                        ident: "Trait",
+                    },
+                ],
+            },
+        )),
+        self_ty: Type::Group {
+            elem: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Type",
+                        },
+                    ],
+                },
+            },
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_supertraits() {
+    // Rustc parses all of the following.
+
+    #[rustfmt::skip]
+    let tokens = quote!(trait Trait where {});
+    snapshot!(tokens as ItemTrait, @r###"
+    ItemTrait {
+        vis: Visibility::Inherited,
+        ident: "Trait",
+        generics: Generics {
+            where_clause: Some(WhereClause),
+        },
+    }
+    "###);
+
+    #[rustfmt::skip]
+    let tokens = quote!(trait Trait: where {});
+    snapshot!(tokens as ItemTrait, @r###"
+    ItemTrait {
+        vis: Visibility::Inherited,
+        ident: "Trait",
+        generics: Generics {
+            where_clause: Some(WhereClause),
+        },
+        colon_token: Some,
+    }
+    "###);
+
+    #[rustfmt::skip]
+    let tokens = quote!(trait Trait: Sized where {});
+    snapshot!(tokens as ItemTrait, @r###"
+    ItemTrait {
+        vis: Visibility::Inherited,
+        ident: "Trait",
+        generics: Generics {
+            where_clause: Some(WhereClause),
+        },
+        colon_token: Some,
+        supertraits: [
+            TypeParamBound::Trait(TraitBound {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Sized",
+                        },
+                    ],
+                },
+            }),
+        ],
+    }
+    "###);
+
+    #[rustfmt::skip]
+    let tokens = quote!(trait Trait: Sized + where {});
+    snapshot!(tokens as ItemTrait, @r###"
+    ItemTrait {
+        vis: Visibility::Inherited,
+        ident: "Trait",
+        generics: Generics {
+            where_clause: Some(WhereClause),
+        },
+        colon_token: Some,
+        supertraits: [
+            TypeParamBound::Trait(TraitBound {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Sized",
+                        },
+                    ],
+                },
+            }),
+            Token![+],
+        ],
+    }
+    "###);
+}
+
+#[test]
+fn test_type_empty_bounds() {
+    #[rustfmt::skip]
+    let tokens = quote! {
+        trait Foo {
+            type Bar: ;
+        }
+    };
+
+    snapshot!(tokens as ItemTrait, @r###"
+    ItemTrait {
+        vis: Visibility::Inherited,
+        ident: "Foo",
+        generics: Generics,
+        items: [
+            TraitItem::Type {
+                ident: "Bar",
+                generics: Generics,
+                colon_token: Some,
+            },
+        ],
+    }
+    "###);
+}
+
+#[test]
+fn test_impl_visibility() {
+    let tokens = quote! {
+        pub default unsafe impl union {}
+    };
+
+    snapshot!(tokens as Item, @"Item::Verbatim(`pub default unsafe impl union { }`)");
+}
+
+#[test]
+fn test_impl_type_parameter_defaults() {
+    #[cfg(any())]
+    impl<T = ()> () {}
+    let tokens = quote! {
+        impl<T = ()> () {}
+    };
+    snapshot!(tokens as Item, @r###"
+    Item::Impl {
+        generics: Generics {
+            lt_token: Some,
+            params: [
+                GenericParam::Type(TypeParam {
+                    ident: "T",
+                    eq_token: Some,
+                    default: Some(Type::Tuple),
+                }),
+            ],
+            gt_token: Some,
+        },
+        self_ty: Type::Tuple,
+    }
+    "###);
+}
+
+#[test]
+fn test_impl_trait_trailing_plus() {
+    let tokens = quote! {
+        fn f() -> impl Sized + {}
+    };
+
+    snapshot!(tokens as Item, @r###"
+    Item::Fn {
+        vis: Visibility::Inherited,
+        sig: Signature {
+            ident: "f",
+            generics: Generics,
+            output: ReturnType::Type(
+                Type::ImplTrait {
+                    bounds: [
+                        TypeParamBound::Trait(TraitBound {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "Sized",
+                                    },
+                                ],
+                            },
+                        }),
+                        Token![+],
+                    ],
+                },
+            ),
+        },
+        block: Block {
+            stmts: [],
+        },
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_iterators.rs b/third_party/rust/syn/tests/test_iterators.rs
new file mode 100644
index 0000000000..5f0eff59e6
--- /dev/null
+++ b/third_party/rust/syn/tests/test_iterators.rs
@@ -0,0 +1,70 @@
+#![allow(clippy::uninlined_format_args)]
+
+use syn::punctuated::{Pair, Punctuated};
+use syn::Token;
+
+#[macro_use]
+mod macros;
+
+macro_rules! check_exact_size_iterator {
+    ($iter:expr) => {{
+        let iter = $iter;
+        let size_hint = iter.size_hint();
+        let len = iter.len();
+        let count = iter.count();
+        assert_eq!(len, count);
+        assert_eq!(size_hint, (count, Some(count)));
+    }};
+}
+
+#[test]
+fn pairs() {
+    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);
+
+    check_exact_size_iterator!(p.pairs());
+    check_exact_size_iterator!(p.pairs_mut());
+    check_exact_size_iterator!(p.into_pairs());
+
+    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);
+
+    assert_eq!(p.pairs().next_back().map(Pair::into_value), Some(&4));
+    assert_eq!(
+        p.pairs_mut().next_back().map(Pair::into_value),
+        Some(&mut 4)
+    );
+    assert_eq!(p.into_pairs().next_back().map(Pair::into_value), Some(4));
+}
+
+#[test]
+fn iter() {
+    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);
+
+    check_exact_size_iterator!(p.iter());
+    check_exact_size_iterator!(p.iter_mut());
+    check_exact_size_iterator!(p.into_iter());
+
+    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);
+
+    assert_eq!(p.iter().next_back(), Some(&4));
+    assert_eq!(p.iter_mut().next_back(), Some(&mut 4));
+    assert_eq!(p.into_iter().next_back(), Some(4));
+}
+
+#[test]
+fn may_dangle() {
+    let p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);
+    for element in &p {
+        if *element == 2 {
+            drop(p);
+            break;
+        }
+    }
+
+    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);
+    for element in &mut p {
+        if *element == 2 {
+            drop(p);
+            break;
+        }
+    }
+}
diff --git a/third_party/rust/syn/tests/test_lit.rs b/third_party/rust/syn/tests/test_lit.rs
new file mode 100644
index 0000000000..bc50136f64
--- /dev/null
+++ b/third_party/rust/syn/tests/test_lit.rs
@@ -0,0 +1,273 @@
+#![allow(
+    clippy::float_cmp,
+    clippy::non_ascii_literal,
+    clippy::single_match_else,
+    clippy::uninlined_format_args
+)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, Literal, Span, TokenStream, TokenTree};
+use quote::ToTokens;
+use std::str::FromStr;
+use syn::{Lit, LitFloat, LitInt, LitStr};
+
+fn lit(s: &str) -> Lit {
+    let mut tokens = TokenStream::from_str(s).unwrap().into_iter();
+    match tokens.next().unwrap() {
+        TokenTree::Literal(lit) => {
+            assert!(tokens.next().is_none());
+            Lit::new(lit)
+        }
+        wrong => panic!("{:?}", wrong),
+    }
+}
+
+#[test]
+fn strings() {
+    fn test_string(s: &str, value: &str) {
+        match lit(s) {
+            Lit::Str(lit) => {
+                assert_eq!(lit.value(), value);
+                let again = lit.into_token_stream().to_string();
+                if again != s {
+                    test_string(&again, value);
+                }
+            }
+            wrong => panic!("{:?}", wrong),
+        }
+    }
+
+    test_string("\"a\"", "a");
+    test_string("\"\\n\"", "\n");
+    test_string("\"\\r\"", "\r");
+    test_string("\"\\t\"", "\t");
+    test_string("\"🐕\"", "🐕"); // NOTE: This is an emoji
+    test_string("\"\\\"\"", "\"");
+    test_string("\"'\"", "'");
+    test_string("\"\"", "");
+    test_string("\"\\u{1F415}\"", "\u{1F415}");
+    test_string("\"\\u{1_2__3_}\"", "\u{123}");
+    test_string(
+        "\"contains\nnewlines\\\nescaped newlines\"",
+        "contains\nnewlinesescaped newlines",
+    );
+    test_string(
+        "\"escaped newline\\\n \x0C unsupported whitespace\"",
+        "escaped newline\x0C unsupported whitespace",
+    );
+    test_string("r\"raw\nstring\\\nhere\"", "raw\nstring\\\nhere");
+    test_string("\"...\"q", "...");
+    test_string("r\"...\"q", "...");
+    test_string("r##\"...\"##q", "...");
+}
+
+#[test]
+fn byte_strings() {
+    fn test_byte_string(s: &str, value: &[u8]) {
+        match lit(s) {
+            Lit::ByteStr(lit) => {
+                assert_eq!(lit.value(), value);
+                let again = lit.into_token_stream().to_string();
+                if again != s {
+                    test_byte_string(&again, value);
+                }
+            }
+            wrong => panic!("{:?}", wrong),
+        }
+    }
+
+    test_byte_string("b\"a\"", b"a");
+    test_byte_string("b\"\\n\"", b"\n");
+    test_byte_string("b\"\\r\"", b"\r");
+    test_byte_string("b\"\\t\"", b"\t");
+    test_byte_string("b\"\\\"\"", b"\"");
+    test_byte_string("b\"'\"", b"'");
+    test_byte_string("b\"\"", b"");
+    test_byte_string(
+        "b\"contains\nnewlines\\\nescaped newlines\"",
+        b"contains\nnewlinesescaped newlines",
+    );
+    test_byte_string("br\"raw\nstring\\\nhere\"", b"raw\nstring\\\nhere");
+    test_byte_string("b\"...\"q", b"...");
+    test_byte_string("br\"...\"q", b"...");
+    test_byte_string("br##\"...\"##q", b"...");
+}
+
+#[test]
+fn bytes() {
+    fn test_byte(s: &str, value: u8) {
+        match lit(s) {
+            Lit::Byte(lit) => {
+                assert_eq!(lit.value(), value);
+                let again = lit.into_token_stream().to_string();
+                assert_eq!(again, s);
+            }
+            wrong => panic!("{:?}", wrong),
+        }
+    }
+
+    test_byte("b'a'", b'a');
+    test_byte("b'\\n'", b'\n');
+    test_byte("b'\\r'", b'\r');
+    test_byte("b'\\t'", b'\t');
+    test_byte("b'\\''", b'\'');
+    test_byte("b'\"'", b'"');
+    test_byte("b'a'q", b'a');
+}
+
+#[test]
+fn chars() {
+    fn test_char(s: &str, value: char) {
+        match lit(s) {
+            Lit::Char(lit) => {
+                assert_eq!(lit.value(), value);
+                let again = lit.into_token_stream().to_string();
+                if again != s {
+                    test_char(&again, value);
+                }
+            }
+            wrong => panic!("{:?}", wrong),
+        }
+    }
+
+    test_char("'a'", 'a');
+    test_char("'\\n'", '\n');
+    test_char("'\\r'", '\r');
+    test_char("'\\t'", '\t');
+    test_char("'🐕'", '🐕'); // NOTE: This is an emoji
+    test_char("'\\''", '\'');
+    test_char("'\"'", '"');
+    test_char("'\\u{1F415}'", '\u{1F415}');
+    test_char("'a'q", 'a');
+}
+
+#[test]
+fn ints() {
+    fn test_int(s: &str, value: u64, suffix: &str) {
+        match lit(s) {
+            Lit::Int(lit) => {
+                assert_eq!(lit.base10_digits().parse::<u64>().unwrap(), value);
+                assert_eq!(lit.suffix(), suffix);
+                let again = lit.into_token_stream().to_string();
+                if again != s {
+                    test_int(&again, value, suffix);
+                }
+            }
+            wrong => panic!("{:?}", wrong),
+        }
+    }
+
+    test_int("5", 5, "");
+    test_int("5u32", 5, "u32");
+    test_int("0E", 0, "E");
+    test_int("0ECMA", 0, "ECMA");
+    test_int("0o0A", 0, "A");
+    test_int("5_0", 50, "");
+    test_int("5_____0_____", 50, "");
+    test_int("0x7f", 127, "");
+    test_int("0x7F", 127, "");
+    test_int("0b1001", 9, "");
+    test_int("0o73", 59, "");
+    test_int("0x7Fu8", 127, "u8");
+    test_int("0b1001i8", 9, "i8");
+    test_int("0o73u32", 59, "u32");
+    test_int("0x__7___f_", 127, "");
+    test_int("0x__7___F_", 127, "");
+    test_int("0b_1_0__01", 9, "");
+    test_int("0o_7__3", 59, "");
+    test_int("0x_7F__u8", 127, "u8");
+    test_int("0b__10__0_1i8", 9, "i8");
+    test_int("0o__7__________________3u32", 59, "u32");
+    test_int("0e1\u{5c5}", 0, "e1\u{5c5}");
+}
+
+#[test]
+fn floats() {
+    fn test_float(s: &str, value: f64, suffix: &str) {
+        match lit(s) {
+            Lit::Float(lit) => {
+                assert_eq!(lit.base10_digits().parse::<f64>().unwrap(), value);
+                assert_eq!(lit.suffix(), suffix);
+                let again = lit.into_token_stream().to_string();
+                if again != s {
+                    test_float(&again, value, suffix);
+                }
+            }
+            wrong => panic!("{:?}", wrong),
+        }
+    }
+
+    test_float("5.5", 5.5, "");
+    test_float("5.5E12", 5.5e12, "");
+    test_float("5.5e12", 5.5e12, "");
+    test_float("1.0__3e-12", 1.03e-12, "");
+    test_float("1.03e+12", 1.03e12, "");
+    test_float("9e99e99", 9e99, "e99");
+    test_float("1e_0", 1.0, "");
+    test_float("0.0ECMA", 0.0, "ECMA");
+}
+
+#[test]
+fn negative() {
+    let span = Span::call_site();
+    assert_eq!("-1", LitInt::new("-1", span).to_string());
+    assert_eq!("-1i8", LitInt::new("-1i8", span).to_string());
+    assert_eq!("-1i16", LitInt::new("-1i16", span).to_string());
+    assert_eq!("-1i32", LitInt::new("-1i32", span).to_string());
+    assert_eq!("-1i64", LitInt::new("-1i64", span).to_string());
+    assert_eq!("-1.5", LitFloat::new("-1.5", span).to_string());
+    assert_eq!("-1.5f32", LitFloat::new("-1.5f32", span).to_string());
+    assert_eq!("-1.5f64", LitFloat::new("-1.5f64", span).to_string());
+}
+
+#[test]
+fn suffix() {
+    fn get_suffix(token: &str) -> String {
+        let lit = syn::parse_str::<Lit>(token).unwrap();
+        match lit {
+            Lit::Str(lit) => lit.suffix().to_owned(),
+            Lit::ByteStr(lit) => lit.suffix().to_owned(),
+            Lit::Byte(lit) => lit.suffix().to_owned(),
+            Lit::Char(lit) => lit.suffix().to_owned(),
+            Lit::Int(lit) => lit.suffix().to_owned(),
+            Lit::Float(lit) => lit.suffix().to_owned(),
+            _ => unimplemented!(),
+        }
+    }
+
+    assert_eq!(get_suffix("\"\"s"), "s");
+    assert_eq!(get_suffix("r\"\"r"), "r");
+    assert_eq!(get_suffix("b\"\"b"), "b");
+    assert_eq!(get_suffix("br\"\"br"), "br");
+    assert_eq!(get_suffix("r#\"\"#r"), "r");
+    assert_eq!(get_suffix("'c'c"), "c");
+    assert_eq!(get_suffix("b'b'b"), "b");
+    assert_eq!(get_suffix("1i32"), "i32");
+    assert_eq!(get_suffix("1_i32"), "i32");
+    assert_eq!(get_suffix("1.0f32"), "f32");
+    assert_eq!(get_suffix("1.0_f32"), "f32");
+}
+
+#[test]
+fn test_deep_group_empty() {
+    let tokens = TokenStream::from_iter(vec![TokenTree::Group(Group::new(
+        Delimiter::None,
+        TokenStream::from_iter(vec![TokenTree::Group(Group::new(
+            Delimiter::None,
+            TokenStream::from_iter(vec![TokenTree::Literal(Literal::string("hi"))]),
+        ))]),
+    ))]);
+
+    snapshot!(tokens as Lit, @r#""hi""# );
+}
+
+#[test]
+fn test_error() {
+    let err = syn::parse_str::<LitStr>("...").unwrap_err();
+    assert_eq!("expected string literal", err.to_string());
+
+    let err = syn::parse_str::<LitStr>("5").unwrap_err();
+    assert_eq!("expected string literal", err.to_string());
+}
diff --git a/third_party/rust/syn/tests/test_meta.rs b/third_party/rust/syn/tests/test_meta.rs
new file mode 100644
index 0000000000..d991c38e45
--- /dev/null
+++ b/third_party/rust/syn/tests/test_meta.rs
@@ -0,0 +1,154 @@
+#![allow(
+    clippy::shadow_unrelated,
+    clippy::too_many_lines,
+    clippy::uninlined_format_args
+)]
+
+#[macro_use]
+mod macros;
+
+use syn::{Meta, MetaList, MetaNameValue};
+
+#[test]
+fn test_parse_meta_item_word() {
+    let input = "hello";
+
+    snapshot!(input as Meta, @r###"
+    Meta::Path {
+        segments: [
+            PathSegment {
+                ident: "hello",
+            },
+        ],
+    }
+    "###);
+}
+
+#[test]
+fn test_parse_meta_name_value() {
+    let input = "foo = 5";
+    let (inner, meta) = (input, input);
+
+    snapshot!(inner as MetaNameValue, @r###"
+    MetaNameValue {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        value: Expr::Lit {
+            lit: 5,
+        },
+    }
+    "###);
+
+    snapshot!(meta as Meta, @r###"
+    Meta::NameValue {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        value: Expr::Lit {
+            lit: 5,
+        },
+    }
+    "###);
+
+    assert_eq!(meta, inner.into());
+}
+
+#[test]
+fn test_parse_meta_item_list_lit() {
+    let input = "foo(5)";
+    let (inner, meta) = (input, input);
+
+    snapshot!(inner as MetaList, @r###"
+    MetaList {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`5`),
+    }
+    "###);
+
+    snapshot!(meta as Meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`5`),
+    }
+    "###);
+
+    assert_eq!(meta, inner.into());
+}
+
+#[test]
+fn test_parse_meta_item_multiple() {
+    let input = "foo(word, name = 5, list(name2 = 6), word2)";
+    let (inner, meta) = (input, input);
+
+    snapshot!(inner as MetaList, @r###"
+    MetaList {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`word , name = 5 , list (name2 = 6) , word2`),
+    }
+    "###);
+
+    snapshot!(meta as Meta, @r###"
+    Meta::List {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "foo",
+                },
+            ],
+        },
+        delimiter: MacroDelimiter::Paren,
+        tokens: TokenStream(`word , name = 5 , list (name2 = 6) , word2`),
+    }
+    "###);
+
+    assert_eq!(meta, inner.into());
+}
+
+#[test]
+fn test_parse_path() {
+    let input = "::serde::Serialize";
+    snapshot!(input as Meta, @r###"
+    Meta::Path {
+        leading_colon: Some,
+        segments: [
+            PathSegment {
+                ident: "serde",
+            },
+            Token![::],
+            PathSegment {
+                ident: "Serialize",
+            },
+        ],
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_parse_buffer.rs b/third_party/rust/syn/tests/test_parse_buffer.rs
new file mode 100644
index 0000000000..2205b50b29
--- /dev/null
+++ b/third_party/rust/syn/tests/test_parse_buffer.rs
@@ -0,0 +1,92 @@
+#![allow(clippy::non_ascii_literal)]
+
+use proc_macro2::{Delimiter, Group, Punct, Spacing, TokenStream, TokenTree};
+use syn::parse::discouraged::Speculative as _;
+use syn::parse::{Parse, ParseStream, Parser, Result};
+use syn::{parenthesized, Token};
+
+#[test]
+#[should_panic(expected = "Fork was not derived from the advancing parse stream")]
+fn smuggled_speculative_cursor_between_sources() {
+    struct BreakRules;
+    impl Parse for BreakRules {
+        fn parse(input1: ParseStream) -> Result<Self> {
+            let nested = |input2: ParseStream| {
+                input1.advance_to(input2);
+                Ok(Self)
+            };
+            nested.parse_str("")
+        }
+    }
+
+    syn::parse_str::<BreakRules>("").unwrap();
+}
+
+#[test]
+#[should_panic(expected = "Fork was not derived from the advancing parse stream")]
+fn smuggled_speculative_cursor_between_brackets() {
+    struct BreakRules;
+    impl Parse for BreakRules {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let a;
+            let b;
+            parenthesized!(a in input);
+            parenthesized!(b in input);
+            a.advance_to(&b);
+            Ok(Self)
+        }
+    }
+
+    syn::parse_str::<BreakRules>("()()").unwrap();
+}
+
+#[test]
+#[should_panic(expected = "Fork was not derived from the advancing parse stream")]
+fn smuggled_speculative_cursor_into_brackets() {
+    struct BreakRules;
+    impl Parse for BreakRules {
+        fn parse(input: ParseStream) -> Result<Self> {
+            let a;
+            parenthesized!(a in input);
+            input.advance_to(&a);
+            Ok(Self)
+        }
+    }
+
+    syn::parse_str::<BreakRules>("()").unwrap();
+}
+
+#[test]
+fn trailing_empty_none_group() {
+    fn parse(input: ParseStream) -> Result<()> {
+        input.parse::<Token![+]>()?;
+
+        let content;
+        parenthesized!(content in input);
+        content.parse::<Token![+]>()?;
+
+        Ok(())
+    }
+
+    // `+ ( + <Ø Ø> ) <Ø <Ø Ø> Ø>`
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Punct(Punct::new('+', Spacing::Alone)),
+        TokenTree::Group(Group::new(
+            Delimiter::Parenthesis,
+            TokenStream::from_iter(vec![
+                TokenTree::Punct(Punct::new('+', Spacing::Alone)),
+                TokenTree::Group(Group::new(Delimiter::None, TokenStream::new())),
+            ]),
+        )),
+        TokenTree::Group(Group::new(Delimiter::None, TokenStream::new())),
+        TokenTree::Group(Group::new(
+            Delimiter::None,
+            TokenStream::from_iter(vec![TokenTree::Group(Group::new(
+                Delimiter::None,
+                TokenStream::new(),
+            ))]),
+        )),
+    ]);
+
+    parse.parse2(tokens).unwrap();
+}
diff --git a/third_party/rust/syn/tests/test_parse_quote.rs b/third_party/rust/syn/tests/test_parse_quote.rs
new file mode 100644
index 0000000000..73aae709af
--- /dev/null
+++ b/third_party/rust/syn/tests/test_parse_quote.rs
@@ -0,0 +1,164 @@
+#[macro_use]
+mod macros;
+
+use syn::punctuated::Punctuated;
+use syn::{parse_quote, Attribute, Field, Lit, Pat, Stmt, Token};
+
+#[test]
+fn test_attribute() {
+    let attr: Attribute = parse_quote!(#[test]);
+    snapshot!(attr, @r###"
+    Attribute {
+        style: AttrStyle::Outer,
+        meta: Meta::Path {
+            segments: [
+                PathSegment {
+                    ident: "test",
+                },
+            ],
+        },
+    }
+    "###);
+
+    let attr: Attribute = parse_quote!(#![no_std]);
+    snapshot!(attr, @r###"
+    Attribute {
+        style: AttrStyle::Inner,
+        meta: Meta::Path {
+            segments: [
+                PathSegment {
+                    ident: "no_std",
+                },
+            ],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_field() {
+    let field: Field = parse_quote!(pub enabled: bool);
+    snapshot!(field, @r###"
+    Field {
+        vis: Visibility::Public,
+        ident: Some("enabled"),
+        colon_token: Some,
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "bool",
+                    },
+                ],
+            },
+        },
+    }
+    "###);
+
+    let field: Field = parse_quote!(primitive::bool);
+    snapshot!(field, @r###"
+    Field {
+        vis: Visibility::Inherited,
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "primitive",
+                    },
+                    Token![::],
+                    PathSegment {
+                        ident: "bool",
+                    },
+                ],
+            },
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_pat() {
+    let pat: Pat = parse_quote!(Some(false) | None);
+    snapshot!(&pat, @r###"
+    Pat::Or {
+        cases: [
+            Pat::TupleStruct {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Some",
+                        },
+                    ],
+                },
+                elems: [
+                    Pat::Lit(ExprLit {
+                        lit: Lit::Bool {
+                            value: false,
+                        },
+                    }),
+                ],
+            },
+            Token![|],
+            Pat::Ident {
+                ident: "None",
+            },
+        ],
+    }
+    "###);
+
+    let boxed_pat: Box<Pat> = parse_quote!(Some(false) | None);
+    assert_eq!(*boxed_pat, pat);
+}
+
+#[test]
+fn test_punctuated() {
+    let punctuated: Punctuated<Lit, Token![|]> = parse_quote!(true | true);
+    snapshot!(punctuated, @r###"
+    [
+        Lit::Bool {
+            value: true,
+        },
+        Token![|],
+        Lit::Bool {
+            value: true,
+        },
+    ]
+    "###);
+
+    let punctuated: Punctuated<Lit, Token![|]> = parse_quote!(true | true |);
+    snapshot!(punctuated, @r###"
+    [
+        Lit::Bool {
+            value: true,
+        },
+        Token![|],
+        Lit::Bool {
+            value: true,
+        },
+        Token![|],
+    ]
+    "###);
+}
+
+#[test]
+fn test_vec_stmt() {
+    let stmts: Vec<Stmt> = parse_quote! {
+        let _;
+        true
+    };
+    snapshot!(stmts, @r###"
+    [
+        Stmt::Local {
+            pat: Pat::Wild,
+        },
+        Stmt::Expr(
+            Expr::Lit {
+                lit: Lit::Bool {
+                    value: true,
+                },
+            },
+            None,
+        ),
+    ]
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_parse_stream.rs b/third_party/rust/syn/tests/test_parse_stream.rs
new file mode 100644
index 0000000000..6e4a5a505f
--- /dev/null
+++ b/third_party/rust/syn/tests/test_parse_stream.rs
@@ -0,0 +1,14 @@
+#![allow(clippy::let_underscore_untyped)]
+
+use syn::ext::IdentExt as _;
+use syn::parse::ParseStream;
+use syn::{Ident, Token};
+
+#[test]
+fn test_peek() {
+    let _ = |input: ParseStream| {
+        let _ = input.peek(Ident);
+        let _ = input.peek(Ident::peek_any);
+        let _ = input.peek(Token![::]);
+    };
+}
diff --git a/third_party/rust/syn/tests/test_pat.rs b/third_party/rust/syn/tests/test_pat.rs
new file mode 100644
index 0000000000..7b5f8b0257
--- /dev/null
+++ b/third_party/rust/syn/tests/test_pat.rs
@@ -0,0 +1,152 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, TokenStream, TokenTree};
+use quote::{quote, ToTokens as _};
+use syn::parse::Parser;
+use syn::punctuated::Punctuated;
+use syn::{parse_quote, token, Item, Pat, PatTuple, Stmt, Token};
+
+#[test]
+fn test_pat_ident() {
+    match Pat::parse_single.parse2(quote!(self)).unwrap() {
+        Pat::Ident(_) => (),
+        value => panic!("expected PatIdent, got {:?}", value),
+    }
+}
+
+#[test]
+fn test_pat_path() {
+    match Pat::parse_single.parse2(quote!(self::CONST)).unwrap() {
+        Pat::Path(_) => (),
+        value => panic!("expected PatPath, got {:?}", value),
+    }
+}
+
+#[test]
+fn test_leading_vert() {
+    // https://github.com/rust-lang/rust/blob/1.43.0/src/test/ui/or-patterns/remove-leading-vert.rs
+
+    syn::parse_str::<Item>("fn f() {}").unwrap();
+    syn::parse_str::<Item>("fn fun1(| A: E) {}").unwrap_err();
+    syn::parse_str::<Item>("fn fun2(|| A: E) {}").unwrap_err();
+
+    syn::parse_str::<Stmt>("let | () = ();").unwrap_err();
+    syn::parse_str::<Stmt>("let (| A): E;").unwrap();
+    syn::parse_str::<Stmt>("let (|| A): (E);").unwrap_err();
+    syn::parse_str::<Stmt>("let (| A,): (E,);").unwrap();
+    syn::parse_str::<Stmt>("let [| A]: [E; 1];").unwrap();
+    syn::parse_str::<Stmt>("let [|| A]: [E; 1];").unwrap_err();
+    syn::parse_str::<Stmt>("let TS(| A): TS;").unwrap();
+    syn::parse_str::<Stmt>("let TS(|| A): TS;").unwrap_err();
+    syn::parse_str::<Stmt>("let NS { f: | A }: NS;").unwrap();
+    syn::parse_str::<Stmt>("let NS { f: || A }: NS;").unwrap_err();
+}
+
+#[test]
+fn test_group() {
+    let group = Group::new(Delimiter::None, quote!(Some(_)));
+    let tokens = TokenStream::from_iter(vec![TokenTree::Group(group)]);
+    let pat = Pat::parse_single.parse2(tokens).unwrap();
+
+    snapshot!(pat, @r###"
+    Pat::TupleStruct {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "Some",
+                },
+            ],
+        },
+        elems: [
+            Pat::Wild,
+        ],
+    }
+    "###);
+}
+
+#[test]
+fn test_ranges() {
+    Pat::parse_single.parse_str("..").unwrap();
+    Pat::parse_single.parse_str("..hi").unwrap();
+    Pat::parse_single.parse_str("lo..").unwrap();
+    Pat::parse_single.parse_str("lo..hi").unwrap();
+
+    Pat::parse_single.parse_str("..=").unwrap_err();
+    Pat::parse_single.parse_str("..=hi").unwrap();
+    Pat::parse_single.parse_str("lo..=").unwrap_err();
+    Pat::parse_single.parse_str("lo..=hi").unwrap();
+
+    Pat::parse_single.parse_str("...").unwrap_err();
+    Pat::parse_single.parse_str("...hi").unwrap_err();
+    Pat::parse_single.parse_str("lo...").unwrap_err();
+    Pat::parse_single.parse_str("lo...hi").unwrap();
+
+    Pat::parse_single.parse_str("[lo..]").unwrap_err();
+    Pat::parse_single.parse_str("[..=hi]").unwrap_err();
+    Pat::parse_single.parse_str("[(lo..)]").unwrap();
+    Pat::parse_single.parse_str("[(..=hi)]").unwrap();
+    Pat::parse_single.parse_str("[lo..=hi]").unwrap();
+
+    Pat::parse_single.parse_str("[_, lo.., _]").unwrap_err();
+    Pat::parse_single.parse_str("[_, ..=hi, _]").unwrap_err();
+    Pat::parse_single.parse_str("[_, (lo..), _]").unwrap();
+    Pat::parse_single.parse_str("[_, (..=hi), _]").unwrap();
+    Pat::parse_single.parse_str("[_, lo..=hi, _]").unwrap();
+}
+
+#[test]
+fn test_tuple_comma() {
+    let mut expr = PatTuple {
+        attrs: Vec::new(),
+        paren_token: token::Paren::default(),
+        elems: Punctuated::new(),
+    };
+    snapshot!(expr.to_token_stream() as Pat, @"Pat::Tuple");
+
+    expr.elems.push_value(parse_quote!(_));
+    // Must not parse to Pat::Paren
+    snapshot!(expr.to_token_stream() as Pat, @r###"
+    Pat::Tuple {
+        elems: [
+            Pat::Wild,
+            Token![,],
+        ],
+    }
+    "###);
+
+    expr.elems.push_punct(<Token![,]>::default());
+    snapshot!(expr.to_token_stream() as Pat, @r###"
+    Pat::Tuple {
+        elems: [
+            Pat::Wild,
+            Token![,],
+        ],
+    }
+    "###);
+
+    expr.elems.push_value(parse_quote!(_));
+    snapshot!(expr.to_token_stream() as Pat, @r###"
+    Pat::Tuple {
+        elems: [
+            Pat::Wild,
+            Token![,],
+            Pat::Wild,
+        ],
+    }
+    "###);
+
+    expr.elems.push_punct(<Token![,]>::default());
+    snapshot!(expr.to_token_stream() as Pat, @r###"
+    Pat::Tuple {
+        elems: [
+            Pat::Wild,
+            Token![,],
+            Pat::Wild,
+            Token![,],
+        ],
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_path.rs b/third_party/rust/syn/tests/test_path.rs
new file mode 100644
index 0000000000..2873441abd
--- /dev/null
+++ b/third_party/rust/syn/tests/test_path.rs
@@ -0,0 +1,130 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
+use quote::{quote, ToTokens};
+use syn::{parse_quote, Expr, Type, TypePath};
+
+#[test]
+fn parse_interpolated_leading_component() {
+    // mimics the token stream corresponding to `$mod::rest`
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Group(Group::new(Delimiter::None, quote! { first })),
+        TokenTree::Punct(Punct::new(':', Spacing::Joint)),
+        TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+        TokenTree::Ident(Ident::new("rest", Span::call_site())),
+    ]);
+
+    snapshot!(tokens.clone() as Expr, @r###"
+    Expr::Path {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "first",
+                },
+                Token![::],
+                PathSegment {
+                    ident: "rest",
+                },
+            ],
+        },
+    }
+    "###);
+
+    snapshot!(tokens as Type, @r###"
+    Type::Path {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "first",
+                },
+                Token![::],
+                PathSegment {
+                    ident: "rest",
+                },
+            ],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn print_incomplete_qpath() {
+    // qpath with `as` token
+    let mut ty: TypePath = parse_quote!(<Self as A>::Q);
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`< Self as A > :: Q`)
+    "###);
+    assert!(ty.path.segments.pop().is_some());
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`< Self as A > ::`)
+    "###);
+    assert!(ty.path.segments.pop().is_some());
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`< Self >`)
+    "###);
+    assert!(ty.path.segments.pop().is_none());
+
+    // qpath without `as` token
+    let mut ty: TypePath = parse_quote!(<Self>::A::B);
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`< Self > :: A :: B`)
+    "###);
+    assert!(ty.path.segments.pop().is_some());
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`< Self > :: A ::`)
+    "###);
+    assert!(ty.path.segments.pop().is_some());
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`< Self > ::`)
+    "###);
+    assert!(ty.path.segments.pop().is_none());
+
+    // normal path
+    let mut ty: TypePath = parse_quote!(Self::A::B);
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`Self :: A :: B`)
+    "###);
+    assert!(ty.path.segments.pop().is_some());
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`Self :: A ::`)
+    "###);
+    assert!(ty.path.segments.pop().is_some());
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(`Self ::`)
+    "###);
+    assert!(ty.path.segments.pop().is_some());
+    snapshot!(ty.to_token_stream(), @r###"
+    TokenStream(``)
+    "###);
+    assert!(ty.path.segments.pop().is_none());
+}
+
+#[test]
+fn parse_parenthesized_path_arguments_with_disambiguator() {
+    #[rustfmt::skip]
+    let tokens = quote!(dyn FnOnce::() -> !);
+    snapshot!(tokens as Type, @r###"
+    Type::TraitObject {
+        dyn_token: Some,
+        bounds: [
+            TypeParamBound::Trait(TraitBound {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "FnOnce",
+                            arguments: PathArguments::Parenthesized {
+                                output: ReturnType::Type(
+                                    Type::Never,
+                                ),
+                            },
+                        },
+                    ],
+                },
+            }),
+        ],
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_precedence.rs b/third_party/rust/syn/tests/test_precedence.rs
new file mode 100644
index 0000000000..026bece505
--- /dev/null
+++ b/third_party/rust/syn/tests/test_precedence.rs
@@ -0,0 +1,548 @@
+//! This test does the following for every file in the rust-lang/rust repo:
+//!
+//! 1. Parse the file using syn into a syn::File.
+//! 2. Extract every syn::Expr from the file.
+//! 3. Print each expr to a string of source code.
+//! 4. Parse the source code using librustc_parse into a rustc_ast::Expr.
+//! 5. For both the syn::Expr and rustc_ast::Expr, crawl the syntax tree to
+//!    insert parentheses surrounding every subexpression.
+//! 6. Serialize the fully parenthesized syn::Expr to a string of source code.
+//! 7. Parse the fully parenthesized source code using librustc_parse.
+//! 8. Compare the rustc_ast::Expr resulting from parenthesizing using rustc
+//!    data structures vs syn data structures, ignoring spans. If they agree,
+//!    rustc's parser and syn's parser have identical handling of expression
+//!    precedence.
+
+#![cfg(not(syn_disable_nightly_tests))]
+#![cfg(not(miri))]
+#![recursion_limit = "1024"]
+#![feature(rustc_private)]
+#![allow(
+    clippy::blocks_in_conditions,
+    clippy::doc_markdown,
+    clippy::explicit_deref_methods,
+    clippy::let_underscore_untyped,
+    clippy::manual_assert,
+    clippy::manual_let_else,
+    clippy::match_like_matches_macro,
+    clippy::match_wildcard_for_single_variants,
+    clippy::too_many_lines,
+    clippy::uninlined_format_args
+)]
+
+extern crate rustc_ast;
+extern crate rustc_ast_pretty;
+extern crate rustc_data_structures;
+extern crate rustc_driver;
+extern crate rustc_span;
+extern crate smallvec;
+extern crate thin_vec;
+
+use crate::common::eq::SpanlessEq;
+use crate::common::parse;
+use quote::ToTokens;
+use rustc_ast::ast;
+use rustc_ast::ptr::P;
+use rustc_ast_pretty::pprust;
+use rustc_span::edition::Edition;
+use std::fs;
+use std::path::Path;
+use std::process;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+#[macro_use]
+mod macros;
+
+#[allow(dead_code)]
+mod common;
+
+mod repo;
+
+#[test]
+fn test_rustc_precedence() {
+    common::rayon_init();
+    repo::clone_rust();
+    let abort_after = common::abort_after();
+    if abort_after == 0 {
+        panic!("Skipping all precedence tests");
+    }
+
+    let passed = AtomicUsize::new(0);
+    let failed = AtomicUsize::new(0);
+
+    repo::for_each_rust_file(|path| {
+        let content = fs::read_to_string(path).unwrap();
+
+        let (l_passed, l_failed) = match syn::parse_file(&content) {
+            Ok(file) => {
+                let edition = repo::edition(path).parse().unwrap();
+                let exprs = collect_exprs(file);
+                let (l_passed, l_failed) = test_expressions(path, edition, exprs);
+                errorf!(
+                    "=== {}: {} passed | {} failed\n",
+                    path.display(),
+                    l_passed,
+                    l_failed,
+                );
+                (l_passed, l_failed)
+            }
+            Err(msg) => {
+                errorf!("\nFAIL {} - syn failed to parse: {}\n", path.display(), msg);
+                (0, 1)
+            }
+        };
+
+        passed.fetch_add(l_passed, Ordering::Relaxed);
+        let prev_failed = failed.fetch_add(l_failed, Ordering::Relaxed);
+
+        if prev_failed + l_failed >= abort_after {
+            process::exit(1);
+        }
+    });
+
+    let passed = passed.load(Ordering::Relaxed);
+    let failed = failed.load(Ordering::Relaxed);
+
+    errorf!("\n===== Precedence Test Results =====\n");
+    errorf!("{} passed | {} failed\n", passed, failed);
+
+    if failed > 0 {
+        panic!("{} failures", failed);
+    }
+}
+
+fn test_expressions(path: &Path, edition: Edition, exprs: Vec<syn::Expr>) -> (usize, usize) {
+    let mut passed = 0;
+    let mut failed = 0;
+
+    rustc_span::create_session_if_not_set_then(edition, |_| {
+        for expr in exprs {
+            let source_code = expr.to_token_stream().to_string();
+            let librustc_ast = if let Some(e) = librustc_parse_and_rewrite(&source_code) {
+                e
+            } else {
+                failed += 1;
+                errorf!(
+                    "\nFAIL {} - librustc failed to parse original\n",
+                    path.display(),
+                );
+                continue;
+            };
+
+            let syn_parenthesized_code =
+                syn_parenthesize(expr.clone()).to_token_stream().to_string();
+            let syn_ast = if let Some(e) = parse::librustc_expr(&syn_parenthesized_code) {
+                e
+            } else {
+                failed += 1;
+                errorf!(
+                    "\nFAIL {} - librustc failed to parse parenthesized\n",
+                    path.display(),
+                );
+                continue;
+            };
+
+            if !SpanlessEq::eq(&syn_ast, &librustc_ast) {
+                failed += 1;
+                let syn_pretty = pprust::expr_to_string(&syn_ast);
+                let librustc_pretty = pprust::expr_to_string(&librustc_ast);
+                errorf!(
+                    "\nFAIL {}\n{}\nsyn != rustc\n{}\n",
+                    path.display(),
+                    syn_pretty,
+                    librustc_pretty,
+                );
+                continue;
+            }
+
+            let expr_invisible = make_parens_invisible(expr);
+            let Ok(reparsed_expr_invisible) = syn::parse2(expr_invisible.to_token_stream()) else {
+                failed += 1;
+                errorf!(
+                    "\nFAIL {} - syn failed to parse invisible delimiters\n{}\n",
+                    path.display(),
+                    source_code,
+                );
+                continue;
+            };
+            if expr_invisible != reparsed_expr_invisible {
+                failed += 1;
+                errorf!(
+                    "\nFAIL {} - mismatch after parsing invisible delimiters\n{}\n",
+                    path.display(),
+                    source_code,
+                );
+                continue;
+            }
+
+            passed += 1;
+        }
+    });
+
+    (passed, failed)
+}
+
+fn librustc_parse_and_rewrite(input: &str) -> Option<P<ast::Expr>> {
+    parse::librustc_expr(input).map(librustc_parenthesize)
+}
+
+fn librustc_parenthesize(mut librustc_expr: P<ast::Expr>) -> P<ast::Expr> {
+    use rustc_ast::ast::{
+        AssocItem, AssocItemKind, Attribute, BinOpKind, Block, BorrowKind, BoundConstness, Expr,
+        ExprField, ExprKind, GenericArg, GenericBound, ItemKind, Local, LocalKind, Pat, Stmt,
+        StmtKind, StructExpr, StructRest, TraitBoundModifiers, Ty,
+    };
+    use rustc_ast::mut_visit::{
+        noop_flat_map_assoc_item, noop_visit_generic_arg, noop_visit_item_kind, noop_visit_local,
+        noop_visit_param_bound, MutVisitor,
+    };
+    use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
+    use rustc_span::DUMMY_SP;
+    use smallvec::SmallVec;
+    use std::mem;
+    use std::ops::DerefMut;
+    use thin_vec::ThinVec;
+
+    struct FullyParenthesize;
+
+    fn contains_let_chain(expr: &Expr) -> bool {
+        match &expr.kind {
+            ExprKind::Let(..) => true,
+            ExprKind::Binary(binop, left, right) => {
+                binop.node == BinOpKind::And
+                    && (contains_let_chain(left) || contains_let_chain(right))
+            }
+            _ => false,
+        }
+    }
+
+    fn flat_map_field<T: MutVisitor>(mut f: ExprField, vis: &mut T) -> Vec<ExprField> {
+        if f.is_shorthand {
+            noop_visit_expr(&mut f.expr, vis);
+        } else {
+            vis.visit_expr(&mut f.expr);
+        }
+        vec![f]
+    }
+
+    fn flat_map_stmt<T: MutVisitor>(stmt: Stmt, vis: &mut T) -> Vec<Stmt> {
+        let kind = match stmt.kind {
+            // Don't wrap toplevel expressions in statements.
+            StmtKind::Expr(mut e) => {
+                noop_visit_expr(&mut e, vis);
+                StmtKind::Expr(e)
+            }
+            StmtKind::Semi(mut e) => {
+                noop_visit_expr(&mut e, vis);
+                StmtKind::Semi(e)
+            }
+            s => s,
+        };
+
+        vec![Stmt { kind, ..stmt }]
+    }
+
+    fn noop_visit_expr<T: MutVisitor>(e: &mut Expr, vis: &mut T) {
+        use rustc_ast::mut_visit::{noop_visit_expr, visit_attrs};
+        match &mut e.kind {
+            ExprKind::AddrOf(BorrowKind::Raw, ..) => {}
+            ExprKind::Struct(expr) => {
+                let StructExpr {
+                    qself,
+                    path,
+                    fields,
+                    rest,
+                } = expr.deref_mut();
+                vis.visit_qself(qself);
+                vis.visit_path(path);
+                fields.flat_map_in_place(|field| flat_map_field(field, vis));
+                if let StructRest::Base(rest) = rest {
+                    vis.visit_expr(rest);
+                }
+                vis.visit_id(&mut e.id);
+                vis.visit_span(&mut e.span);
+                visit_attrs(&mut e.attrs, vis);
+            }
+            _ => noop_visit_expr(e, vis),
+        }
+    }
+
+    impl MutVisitor for FullyParenthesize {
+        fn visit_expr(&mut self, e: &mut P<Expr>) {
+            noop_visit_expr(e, self);
+            match e.kind {
+                ExprKind::Block(..) | ExprKind::If(..) | ExprKind::Let(..) => {}
+                ExprKind::Binary(..) if contains_let_chain(e) => {}
+                _ => {
+                    let inner = mem::replace(
+                        e,
+                        P(Expr {
+                            id: ast::DUMMY_NODE_ID,
+                            kind: ExprKind::Err,
+                            span: DUMMY_SP,
+                            attrs: ThinVec::new(),
+                            tokens: None,
+                        }),
+                    );
+                    e.kind = ExprKind::Paren(inner);
+                }
+            }
+        }
+
+        fn visit_generic_arg(&mut self, arg: &mut GenericArg) {
+            match arg {
+                // Don't wrap unbraced const generic arg as that's invalid syntax.
+                GenericArg::Const(anon_const) => {
+                    if let ExprKind::Block(..) = &mut anon_const.value.kind {
+                        noop_visit_expr(&mut anon_const.value, self);
+                    }
+                }
+                _ => noop_visit_generic_arg(arg, self),
+            }
+        }
+
+        fn visit_param_bound(&mut self, bound: &mut GenericBound) {
+            match bound {
+                GenericBound::Trait(
+                    _,
+                    TraitBoundModifiers {
+                        constness: BoundConstness::Maybe(_),
+                        ..
+                    },
+                ) => {}
+                _ => noop_visit_param_bound(bound, self),
+            }
+        }
+
+        fn visit_block(&mut self, block: &mut P<Block>) {
+            self.visit_id(&mut block.id);
+            block
+                .stmts
+                .flat_map_in_place(|stmt| flat_map_stmt(stmt, self));
+            self.visit_span(&mut block.span);
+        }
+
+        fn visit_local(&mut self, local: &mut P<Local>) {
+            match local.kind {
+                LocalKind::InitElse(..) => {}
+                _ => noop_visit_local(local, self),
+            }
+        }
+
+        fn visit_item_kind(&mut self, item: &mut ItemKind) {
+            match item {
+                ItemKind::Const(const_item)
+                    if !const_item.generics.params.is_empty()
+                        || !const_item.generics.where_clause.predicates.is_empty() => {}
+                _ => noop_visit_item_kind(item, self),
+            }
+        }
+
+        fn flat_map_trait_item(&mut self, item: P<AssocItem>) -> SmallVec<[P<AssocItem>; 1]> {
+            match &item.kind {
+                AssocItemKind::Const(const_item)
+                    if !const_item.generics.params.is_empty()
+                        || !const_item.generics.where_clause.predicates.is_empty() =>
+                {
+                    SmallVec::from([item])
+                }
+                _ => noop_flat_map_assoc_item(item, self),
+            }
+        }
+
+        fn flat_map_impl_item(&mut self, item: P<AssocItem>) -> SmallVec<[P<AssocItem>; 1]> {
+            match &item.kind {
+                AssocItemKind::Const(const_item)
+                    if !const_item.generics.params.is_empty()
+                        || !const_item.generics.where_clause.predicates.is_empty() =>
+                {
+                    SmallVec::from([item])
+                }
+                _ => noop_flat_map_assoc_item(item, self),
+            }
+        }
+
+        // We don't want to look at expressions that might appear in patterns or
+        // types yet. We'll look into comparing those in the future. For now
+        // focus on expressions appearing in other places.
+        fn visit_pat(&mut self, pat: &mut P<Pat>) {
+            let _ = pat;
+        }
+
+        fn visit_ty(&mut self, ty: &mut P<Ty>) {
+            let _ = ty;
+        }
+
+        fn visit_attribute(&mut self, attr: &mut Attribute) {
+            let _ = attr;
+        }
+    }
+
+    let mut folder = FullyParenthesize;
+    folder.visit_expr(&mut librustc_expr);
+    librustc_expr
+}
+
+fn syn_parenthesize(syn_expr: syn::Expr) -> syn::Expr {
+    use syn::fold::{fold_expr, fold_generic_argument, Fold};
+    use syn::{token, BinOp, Expr, ExprParen, GenericArgument, MetaNameValue, Pat, Stmt, Type};
+
+    struct FullyParenthesize;
+
+    fn parenthesize(expr: Expr) -> Expr {
+        Expr::Paren(ExprParen {
+            attrs: Vec::new(),
+            expr: Box::new(expr),
+            paren_token: token::Paren::default(),
+        })
+    }
+
+    fn needs_paren(expr: &Expr) -> bool {
+        match expr {
+            Expr::Group(_) => unreachable!(),
+            Expr::If(_) | Expr::Unsafe(_) | Expr::Block(_) | Expr::Let(_) => false,
+            Expr::Binary(_) => !contains_let_chain(expr),
+            _ => true,
+        }
+    }
+
+    fn contains_let_chain(expr: &Expr) -> bool {
+        match expr {
+            Expr::Let(_) => true,
+            Expr::Binary(expr) => {
+                matches!(expr.op, BinOp::And(_))
+                    && (contains_let_chain(&expr.left) || contains_let_chain(&expr.right))
+            }
+            _ => false,
+        }
+    }
+
+    impl Fold for FullyParenthesize {
+        fn fold_expr(&mut self, expr: Expr) -> Expr {
+            let needs_paren = needs_paren(&expr);
+            let folded = fold_expr(self, expr);
+            if needs_paren {
+                parenthesize(folded)
+            } else {
+                folded
+            }
+        }
+
+        fn fold_generic_argument(&mut self, arg: GenericArgument) -> GenericArgument {
+            match arg {
+                GenericArgument::Const(arg) => GenericArgument::Const(match arg {
+                    Expr::Block(_) => fold_expr(self, arg),
+                    // Don't wrap unbraced const generic arg as that's invalid syntax.
+                    _ => arg,
+                }),
+                _ => fold_generic_argument(self, arg),
+            }
+        }
+
+        fn fold_stmt(&mut self, stmt: Stmt) -> Stmt {
+            match stmt {
+                // Don't wrap toplevel expressions in statements.
+                Stmt::Expr(Expr::Verbatim(_), Some(_)) => stmt,
+                Stmt::Expr(e, semi) => Stmt::Expr(fold_expr(self, e), semi),
+                s => s,
+            }
+        }
+
+        fn fold_meta_name_value(&mut self, meta: MetaNameValue) -> MetaNameValue {
+            // Don't turn #[p = "..."] into #[p = ("...")].
+            meta
+        }
+
+        // We don't want to look at expressions that might appear in patterns or
+        // types yet. We'll look into comparing those in the future. For now
+        // focus on expressions appearing in other places.
+        fn fold_pat(&mut self, pat: Pat) -> Pat {
+            pat
+        }
+
+        fn fold_type(&mut self, ty: Type) -> Type {
+            ty
+        }
+    }
+
+    let mut folder = FullyParenthesize;
+    folder.fold_expr(syn_expr)
+}
+
+fn make_parens_invisible(expr: syn::Expr) -> syn::Expr {
+    use syn::fold::{fold_expr, fold_stmt, Fold};
+    use syn::{token, Expr, ExprGroup, ExprParen, Stmt};
+
+    struct MakeParensInvisible;
+
+    impl Fold for MakeParensInvisible {
+        fn fold_expr(&mut self, mut expr: Expr) -> Expr {
+            if let Expr::Paren(paren) = expr {
+                expr = Expr::Group(ExprGroup {
+                    attrs: paren.attrs,
+                    group_token: token::Group(paren.paren_token.span.join()),
+                    expr: paren.expr,
+                });
+            }
+            fold_expr(self, expr)
+        }
+
+        fn fold_stmt(&mut self, stmt: Stmt) -> Stmt {
+            if let Stmt::Expr(expr @ (Expr::Binary(_) | Expr::Cast(_)), None) = stmt {
+                Stmt::Expr(
+                    Expr::Paren(ExprParen {
+                        attrs: Vec::new(),
+                        paren_token: token::Paren::default(),
+                        expr: Box::new(fold_expr(self, expr)),
+                    }),
+                    None,
+                )
+            } else {
+                fold_stmt(self, stmt)
+            }
+        }
+    }
+
+    let mut folder = MakeParensInvisible;
+    folder.fold_expr(expr)
+}
+
+/// Walk through a crate collecting all expressions we can find in it.
+fn collect_exprs(file: syn::File) -> Vec<syn::Expr> {
+    use syn::fold::Fold;
+    use syn::punctuated::Punctuated;
+    use syn::{token, ConstParam, Expr, ExprTuple, Pat, Path};
+
+    struct CollectExprs(Vec<Expr>);
+    impl Fold for CollectExprs {
+        fn fold_expr(&mut self, expr: Expr) -> Expr {
+            match expr {
+                Expr::Verbatim(_) => {}
+                _ => self.0.push(expr),
+            }
+
+            Expr::Tuple(ExprTuple {
+                attrs: vec![],
+                elems: Punctuated::new(),
+                paren_token: token::Paren::default(),
+            })
+        }
+
+        fn fold_pat(&mut self, pat: Pat) -> Pat {
+            pat
+        }
+
+        fn fold_path(&mut self, path: Path) -> Path {
+            // Skip traversing into const generic path arguments
+            path
+        }
+
+        fn fold_const_param(&mut self, const_param: ConstParam) -> ConstParam {
+            const_param
+        }
+    }
+
+    let mut folder = CollectExprs(vec![]);
+    folder.fold_file(file);
+    folder.0
+}
diff --git a/third_party/rust/syn/tests/test_receiver.rs b/third_party/rust/syn/tests/test_receiver.rs
new file mode 100644
index 0000000000..8decb555c5
--- /dev/null
+++ b/third_party/rust/syn/tests/test_receiver.rs
@@ -0,0 +1,321 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use syn::{parse_quote, TraitItemFn};
+
+#[test]
+fn test_by_value() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn by_value(self: Self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        colon_token: Some,
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "Self",
+                    },
+                ],
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_by_mut_value() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn by_mut(mut self: Self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        mutability: Some,
+        colon_token: Some,
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "Self",
+                    },
+                ],
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_by_ref() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn by_ref(self: &Self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        colon_token: Some,
+        ty: Type::Reference {
+            elem: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Self",
+                        },
+                    ],
+                },
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_by_box() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn by_box(self: Box<Self>);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        colon_token: Some,
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "Box",
+                        arguments: PathArguments::AngleBracketed {
+                            args: [
+                                GenericArgument::Type(Type::Path {
+                                    path: Path {
+                                        segments: [
+                                            PathSegment {
+                                                ident: "Self",
+                                            },
+                                        ],
+                                    },
+                                }),
+                            ],
+                        },
+                    },
+                ],
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_by_pin() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn by_pin(self: Pin<Self>);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        colon_token: Some,
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "Pin",
+                        arguments: PathArguments::AngleBracketed {
+                            args: [
+                                GenericArgument::Type(Type::Path {
+                                    path: Path {
+                                        segments: [
+                                            PathSegment {
+                                                ident: "Self",
+                                            },
+                                        ],
+                                    },
+                                }),
+                            ],
+                        },
+                    },
+                ],
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_explicit_type() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn explicit_type(self: Pin<MyType>);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        colon_token: Some,
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "Pin",
+                        arguments: PathArguments::AngleBracketed {
+                            args: [
+                                GenericArgument::Type(Type::Path {
+                                    path: Path {
+                                        segments: [
+                                            PathSegment {
+                                                ident: "MyType",
+                                            },
+                                        ],
+                                    },
+                                }),
+                            ],
+                        },
+                    },
+                ],
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_value_shorthand() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn value_shorthand(self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "Self",
+                    },
+                ],
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_mut_value_shorthand() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn mut_value_shorthand(mut self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        mutability: Some,
+        ty: Type::Path {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "Self",
+                    },
+                ],
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_ref_shorthand() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn ref_shorthand(&self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        reference: Some(None),
+        ty: Type::Reference {
+            elem: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Self",
+                        },
+                    ],
+                },
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_ref_shorthand_with_lifetime() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn ref_shorthand(&'a self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        reference: Some(Some(Lifetime {
+            ident: "a",
+        })),
+        ty: Type::Reference {
+            lifetime: Some(Lifetime {
+                ident: "a",
+            }),
+            elem: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Self",
+                        },
+                    ],
+                },
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_ref_mut_shorthand() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn ref_mut_shorthand(&mut self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        reference: Some(None),
+        mutability: Some,
+        ty: Type::Reference {
+            mutability: Some,
+            elem: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Self",
+                        },
+                    ],
+                },
+            },
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_ref_mut_shorthand_with_lifetime() {
+    let TraitItemFn { sig, .. } = parse_quote! {
+        fn ref_mut_shorthand(&'a mut self);
+    };
+    snapshot!(&sig.inputs[0], @r###"
+    FnArg::Receiver(Receiver {
+        reference: Some(Some(Lifetime {
+            ident: "a",
+        })),
+        mutability: Some,
+        ty: Type::Reference {
+            lifetime: Some(Lifetime {
+                ident: "a",
+            }),
+            mutability: Some,
+            elem: Type::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Self",
+                        },
+                    ],
+                },
+            },
+        },
+    })
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_round_trip.rs b/third_party/rust/syn/tests/test_round_trip.rs
new file mode 100644
index 0000000000..a673fffa74
--- /dev/null
+++ b/third_party/rust/syn/tests/test_round_trip.rs
@@ -0,0 +1,239 @@
+#![cfg(not(syn_disable_nightly_tests))]
+#![cfg(not(miri))]
+#![recursion_limit = "1024"]
+#![feature(rustc_private)]
+#![allow(
+    clippy::blocks_in_conditions,
+    clippy::manual_assert,
+    clippy::manual_let_else,
+    clippy::match_like_matches_macro,
+    clippy::uninlined_format_args
+)]
+
+extern crate rustc_ast;
+extern crate rustc_ast_pretty;
+extern crate rustc_data_structures;
+extern crate rustc_driver;
+extern crate rustc_error_messages;
+extern crate rustc_errors;
+extern crate rustc_expand;
+extern crate rustc_parse as parse;
+extern crate rustc_session;
+extern crate rustc_span;
+
+use crate::common::eq::SpanlessEq;
+use quote::quote;
+use rustc_ast::ast::{
+    AngleBracketedArg, AngleBracketedArgs, Crate, GenericArg, GenericParamKind, Generics,
+    WhereClause,
+};
+use rustc_ast::mut_visit::{self, MutVisitor};
+use rustc_ast_pretty::pprust;
+use rustc_error_messages::{DiagnosticMessage, LazyFallbackBundle};
+use rustc_errors::{translation, Diagnostic, PResult};
+use rustc_session::parse::ParseSess;
+use rustc_span::source_map::FilePathMapping;
+use rustc_span::FileName;
+use std::borrow::Cow;
+use std::fs;
+use std::panic;
+use std::path::Path;
+use std::process;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::time::Instant;
+
+#[macro_use]
+mod macros;
+
+#[allow(dead_code)]
+mod common;
+
+mod repo;
+
+#[test]
+fn test_round_trip() {
+    common::rayon_init();
+    repo::clone_rust();
+    let abort_after = common::abort_after();
+    if abort_after == 0 {
+        panic!("Skipping all round_trip tests");
+    }
+
+    let failed = AtomicUsize::new(0);
+
+    repo::for_each_rust_file(|path| test(path, &failed, abort_after));
+
+    let failed = failed.load(Ordering::Relaxed);
+    if failed > 0 {
+        panic!("{} failures", failed);
+    }
+}
+
+fn test(path: &Path, failed: &AtomicUsize, abort_after: usize) {
+    let content = fs::read_to_string(path).unwrap();
+
+    let start = Instant::now();
+    let (krate, elapsed) = match syn::parse_file(&content) {
+        Ok(krate) => (krate, start.elapsed()),
+        Err(msg) => {
+            errorf!("=== {}: syn failed to parse\n{:?}\n", path.display(), msg);
+            let prev_failed = failed.fetch_add(1, Ordering::Relaxed);
+            if prev_failed + 1 >= abort_after {
+                process::exit(1);
+            }
+            return;
+        }
+    };
+    let back = quote!(#krate).to_string();
+    let edition = repo::edition(path).parse().unwrap();
+
+    rustc_span::create_session_if_not_set_then(edition, |_| {
+        let equal = match panic::catch_unwind(|| {
+            let locale_resources = rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec();
+            let file_path_mapping = FilePathMapping::empty();
+            let sess = ParseSess::new(locale_resources, file_path_mapping);
+            let before = match librustc_parse(content, &sess) {
+                Ok(before) => before,
+                Err(diagnostic) => {
+                    errorf!(
+                        "=== {}: ignore - librustc failed to parse original content: {}\n",
+                        path.display(),
+                        translate_message(&diagnostic),
+                    );
+                    diagnostic.cancel();
+                    return Err(true);
+                }
+            };
+            let after = match librustc_parse(back, &sess) {
+                Ok(after) => after,
+                Err(mut diagnostic) => {
+                    errorf!("=== {}: librustc failed to parse", path.display());
+                    diagnostic.emit();
+                    return Err(false);
+                }
+            };
+            Ok((before, after))
+        }) {
+            Err(_) => {
+                errorf!("=== {}: ignoring librustc panic\n", path.display());
+                true
+            }
+            Ok(Err(equal)) => equal,
+            Ok(Ok((mut before, mut after))) => {
+                normalize(&mut before);
+                normalize(&mut after);
+                if SpanlessEq::eq(&before, &after) {
+                    errorf!(
+                        "=== {}: pass in {}ms\n",
+                        path.display(),
+                        elapsed.as_secs() * 1000 + u64::from(elapsed.subsec_nanos()) / 1_000_000
+                    );
+                    true
+                } else {
+                    errorf!(
+                        "=== {}: FAIL\n{}\n!=\n{}\n",
+                        path.display(),
+                        pprust::crate_to_string_for_macros(&before),
+                        pprust::crate_to_string_for_macros(&after),
+                    );
+                    false
+                }
+            }
+        };
+        if !equal {
+            let prev_failed = failed.fetch_add(1, Ordering::Relaxed);
+            if prev_failed + 1 >= abort_after {
+                process::exit(1);
+            }
+        }
+    });
+}
+
+fn librustc_parse(content: String, sess: &ParseSess) -> PResult<Crate> {
+    static COUNTER: AtomicUsize = AtomicUsize::new(0);
+    let counter = COUNTER.fetch_add(1, Ordering::Relaxed);
+    let name = FileName::Custom(format!("test_round_trip{}", counter));
+    parse::parse_crate_from_source_str(name, content, sess)
+}
+
+fn translate_message(diagnostic: &Diagnostic) -> Cow<'static, str> {
+    thread_local! {
+        static FLUENT_BUNDLE: LazyFallbackBundle = {
+            let locale_resources = rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec();
+            let with_directionality_markers = false;
+            rustc_error_messages::fallback_fluent_bundle(locale_resources, with_directionality_markers)
+        };
+    }
+
+    let message = &diagnostic.messages[0].0;
+    let args = translation::to_fluent_args(diagnostic.args());
+
+    let (identifier, attr) = match message {
+        DiagnosticMessage::Str(msg) | DiagnosticMessage::Eager(msg) => return msg.clone(),
+        DiagnosticMessage::FluentIdentifier(identifier, attr) => (identifier, attr),
+    };
+
+    FLUENT_BUNDLE.with(|fluent_bundle| {
+        let message = fluent_bundle
+            .get_message(identifier)
+            .expect("missing diagnostic in fluent bundle");
+        let value = match attr {
+            Some(attr) => message
+                .get_attribute(attr)
+                .expect("missing attribute in fluent message")
+                .value(),
+            None => message.value().expect("missing value in fluent message"),
+        };
+
+        let mut err = Vec::new();
+        let translated = fluent_bundle.format_pattern(value, Some(&args), &mut err);
+        assert!(err.is_empty());
+        Cow::Owned(translated.into_owned())
+    })
+}
+
+fn normalize(krate: &mut Crate) {
+    struct NormalizeVisitor;
+
+    impl MutVisitor for NormalizeVisitor {
+        fn visit_angle_bracketed_parameter_data(&mut self, e: &mut AngleBracketedArgs) {
+            #[derive(Ord, PartialOrd, Eq, PartialEq)]
+            enum Group {
+                Lifetimes,
+                TypesAndConsts,
+                Constraints,
+            }
+            e.args.sort_by_key(|arg| match arg {
+                AngleBracketedArg::Arg(arg) => match arg {
+                    GenericArg::Lifetime(_) => Group::Lifetimes,
+                    GenericArg::Type(_) | GenericArg::Const(_) => Group::TypesAndConsts,
+                },
+                AngleBracketedArg::Constraint(_) => Group::Constraints,
+            });
+            mut_visit::noop_visit_angle_bracketed_parameter_data(e, self);
+        }
+
+        fn visit_generics(&mut self, e: &mut Generics) {
+            #[derive(Ord, PartialOrd, Eq, PartialEq)]
+            enum Group {
+                Lifetimes,
+                TypesAndConsts,
+            }
+            e.params.sort_by_key(|param| match param.kind {
+                GenericParamKind::Lifetime => Group::Lifetimes,
+                GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
+                    Group::TypesAndConsts
+                }
+            });
+            mut_visit::noop_visit_generics(e, self);
+        }
+
+        fn visit_where_clause(&mut self, e: &mut WhereClause) {
+            if e.predicates.is_empty() {
+                e.has_where_token = false;
+            }
+        }
+    }
+
+    NormalizeVisitor.visit_crate(krate);
+}
diff --git a/third_party/rust/syn/tests/test_shebang.rs b/third_party/rust/syn/tests/test_shebang.rs
new file mode 100644
index 0000000000..843916180f
--- /dev/null
+++ b/third_party/rust/syn/tests/test_shebang.rs
@@ -0,0 +1,67 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+#[test]
+fn test_basic() {
+    let content = "#!/usr/bin/env rustx\nfn main() {}";
+    let file = syn::parse_file(content).unwrap();
+    snapshot!(file, @r###"
+    File {
+        shebang: Some("#!/usr/bin/env rustx"),
+        items: [
+            Item::Fn {
+                vis: Visibility::Inherited,
+                sig: Signature {
+                    ident: "main",
+                    generics: Generics,
+                    output: ReturnType::Default,
+                },
+                block: Block {
+                    stmts: [],
+                },
+            },
+        ],
+    }
+    "###);
+}
+
+#[test]
+fn test_comment() {
+    let content = "#!//am/i/a/comment\n[allow(dead_code)] fn main() {}";
+    let file = syn::parse_file(content).unwrap();
+    snapshot!(file, @r###"
+    File {
+        attrs: [
+            Attribute {
+                style: AttrStyle::Inner,
+                meta: Meta::List {
+                    path: Path {
+                        segments: [
+                            PathSegment {
+                                ident: "allow",
+                            },
+                        ],
+                    },
+                    delimiter: MacroDelimiter::Paren,
+                    tokens: TokenStream(`dead_code`),
+                },
+            },
+        ],
+        items: [
+            Item::Fn {
+                vis: Visibility::Inherited,
+                sig: Signature {
+                    ident: "main",
+                    generics: Generics,
+                    output: ReturnType::Default,
+                },
+                block: Block {
+                    stmts: [],
+                },
+            },
+        ],
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_should_parse.rs b/third_party/rust/syn/tests/test_should_parse.rs
new file mode 100644
index 0000000000..180d859916
--- /dev/null
+++ b/third_party/rust/syn/tests/test_should_parse.rs
@@ -0,0 +1,45 @@
+macro_rules! should_parse {
+    ($name:ident, { $($in:tt)* }) => {
+        #[test]
+        fn $name() {
+            // Make sure we can parse the file!
+            syn::parse_file(stringify!($($in)*)).unwrap();
+        }
+    }
+}
+
+should_parse!(generic_associated_type, {
+    impl Foo {
+        type Item = &'a i32;
+        fn foo<'a>(&'a self) -> Self::Item<'a> {}
+    }
+});
+
+#[rustfmt::skip]
+should_parse!(const_generics_use, {
+    type X = Foo<5>;
+    type Y = Foo<"foo">;
+    type Z = Foo<X>;
+    type W = Foo<{ X + 10 }>;
+});
+
+should_parse!(trailing_plus_type, {
+    type A = Box<Foo>;
+    type A = Box<Foo + 'a>;
+    type A = Box<'a + Foo>;
+});
+
+should_parse!(generic_associated_type_where, {
+    trait Foo {
+        type Item;
+        fn foo<T>(&self, t: T) -> Self::Item<T>;
+    }
+});
+
+should_parse!(match_with_block_expr, {
+    fn main() {
+        match false {
+            _ => {}.a(),
+        }
+    }
+});
diff --git a/third_party/rust/syn/tests/test_size.rs b/third_party/rust/syn/tests/test_size.rs
new file mode 100644
index 0000000000..d64a3ab6eb
--- /dev/null
+++ b/third_party/rust/syn/tests/test_size.rs
@@ -0,0 +1,36 @@
+// Assumes proc-macro2's "span-locations" feature is off.
+
+#![cfg(target_pointer_width = "64")]
+
+use std::mem;
+use syn::{Expr, Item, Lit, Pat, Type};
+
+#[rustversion::attr(before(2022-11-24), ignore)]
+#[test]
+fn test_expr_size() {
+    assert_eq!(mem::size_of::<Expr>(), 176);
+}
+
+#[rustversion::attr(before(2022-09-09), ignore)]
+#[test]
+fn test_item_size() {
+    assert_eq!(mem::size_of::<Item>(), 360);
+}
+
+#[rustversion::attr(before(2023-04-29), ignore)]
+#[test]
+fn test_type_size() {
+    assert_eq!(mem::size_of::<Type>(), 232);
+}
+
+#[rustversion::attr(before(2023-04-29), ignore)]
+#[test]
+fn test_pat_size() {
+    assert_eq!(mem::size_of::<Pat>(), 184);
+}
+
+#[rustversion::attr(before(2023-12-20), ignore)]
+#[test]
+fn test_lit_size() {
+    assert_eq!(mem::size_of::<Lit>(), 24);
+}
diff --git a/third_party/rust/syn/tests/test_stmt.rs b/third_party/rust/syn/tests/test_stmt.rs
new file mode 100644
index 0000000000..61890a40ec
--- /dev/null
+++ b/third_party/rust/syn/tests/test_stmt.rs
@@ -0,0 +1,322 @@
+#![allow(
+    clippy::assertions_on_result_states,
+    clippy::non_ascii_literal,
+    clippy::uninlined_format_args
+)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, Ident, Span, TokenStream, TokenTree};
+use quote::{quote, ToTokens as _};
+use syn::parse::Parser as _;
+use syn::{Block, Stmt};
+
+#[test]
+fn test_raw_operator() {
+    let stmt = syn::parse_str::<Stmt>("let _ = &raw const x;").unwrap();
+
+    snapshot!(stmt, @r###"
+    Stmt::Local {
+        pat: Pat::Wild,
+        init: Some(LocalInit {
+            expr: Expr::Verbatim(`& raw const x`),
+        }),
+    }
+    "###);
+}
+
+#[test]
+fn test_raw_variable() {
+    let stmt = syn::parse_str::<Stmt>("let _ = &raw;").unwrap();
+
+    snapshot!(stmt, @r###"
+    Stmt::Local {
+        pat: Pat::Wild,
+        init: Some(LocalInit {
+            expr: Expr::Reference {
+                expr: Expr::Path {
+                    path: Path {
+                        segments: [
+                            PathSegment {
+                                ident: "raw",
+                            },
+                        ],
+                    },
+                },
+            },
+        }),
+    }
+    "###);
+}
+
+#[test]
+fn test_raw_invalid() {
+    assert!(syn::parse_str::<Stmt>("let _ = &raw x;").is_err());
+}
+
+#[test]
+fn test_none_group() {
+    // <Ø async fn f() {} Ø>
+    let tokens = TokenStream::from_iter(vec![TokenTree::Group(Group::new(
+        Delimiter::None,
+        TokenStream::from_iter(vec![
+            TokenTree::Ident(Ident::new("async", Span::call_site())),
+            TokenTree::Ident(Ident::new("fn", Span::call_site())),
+            TokenTree::Ident(Ident::new("f", Span::call_site())),
+            TokenTree::Group(Group::new(Delimiter::Parenthesis, TokenStream::new())),
+            TokenTree::Group(Group::new(Delimiter::Brace, TokenStream::new())),
+        ]),
+    ))]);
+    snapshot!(tokens as Stmt, @r###"
+    Stmt::Item(Item::Fn {
+        vis: Visibility::Inherited,
+        sig: Signature {
+            asyncness: Some,
+            ident: "f",
+            generics: Generics,
+            output: ReturnType::Default,
+        },
+        block: Block {
+            stmts: [],
+        },
+    })
+    "###);
+
+    let tokens = Group::new(Delimiter::None, quote!(let None = None)).to_token_stream();
+    let stmts = Block::parse_within.parse2(tokens).unwrap();
+    snapshot!(stmts, @r###"
+    [
+        Stmt::Expr(
+            Expr::Group {
+                expr: Expr::Let {
+                    pat: Pat::Ident {
+                        ident: "None",
+                    },
+                    expr: Expr::Path {
+                        path: Path {
+                            segments: [
+                                PathSegment {
+                                    ident: "None",
+                                },
+                            ],
+                        },
+                    },
+                },
+            },
+            None,
+        ),
+    ]
+    "###);
+}
+
+#[test]
+fn test_let_dot_dot() {
+    let tokens = quote! {
+        let .. = 10;
+    };
+
+    snapshot!(tokens as Stmt, @r###"
+    Stmt::Local {
+        pat: Pat::Rest,
+        init: Some(LocalInit {
+            expr: Expr::Lit {
+                lit: 10,
+            },
+        }),
+    }
+    "###);
+}
+
+#[test]
+fn test_let_else() {
+    let tokens = quote! {
+        let Some(x) = None else { return 0; };
+    };
+
+    snapshot!(tokens as Stmt, @r###"
+    Stmt::Local {
+        pat: Pat::TupleStruct {
+            path: Path {
+                segments: [
+                    PathSegment {
+                        ident: "Some",
+                    },
+                ],
+            },
+            elems: [
+                Pat::Ident {
+                    ident: "x",
+                },
+            ],
+        },
+        init: Some(LocalInit {
+            expr: Expr::Path {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "None",
+                        },
+                    ],
+                },
+            },
+            diverge: Some(Expr::Block {
+                block: Block {
+                    stmts: [
+                        Stmt::Expr(
+                            Expr::Return {
+                                expr: Some(Expr::Lit {
+                                    lit: 0,
+                                }),
+                            },
+                            Some,
+                        ),
+                    ],
+                },
+            }),
+        }),
+    }
+    "###);
+}
+
+#[test]
+fn test_macros() {
+    let tokens = quote! {
+        fn main() {
+            macro_rules! mac {}
+            thread_local! { static FOO }
+            println!("");
+            vec![]
+        }
+    };
+
+    snapshot!(tokens as Stmt, @r###"
+    Stmt::Item(Item::Fn {
+        vis: Visibility::Inherited,
+        sig: Signature {
+            ident: "main",
+            generics: Generics,
+            output: ReturnType::Default,
+        },
+        block: Block {
+            stmts: [
+                Stmt::Item(Item::Macro {
+                    ident: Some("mac"),
+                    mac: Macro {
+                        path: Path {
+                            segments: [
+                                PathSegment {
+                                    ident: "macro_rules",
+                                },
+                            ],
+                        },
+                        delimiter: MacroDelimiter::Brace,
+                        tokens: TokenStream(``),
+                    },
+                }),
+                Stmt::Macro {
+                    mac: Macro {
+                        path: Path {
+                            segments: [
+                                PathSegment {
+                                    ident: "thread_local",
+                                },
+                            ],
+                        },
+                        delimiter: MacroDelimiter::Brace,
+                        tokens: TokenStream(`static FOO`),
+                    },
+                },
+                Stmt::Macro {
+                    mac: Macro {
+                        path: Path {
+                            segments: [
+                                PathSegment {
+                                    ident: "println",
+                                },
+                            ],
+                        },
+                        delimiter: MacroDelimiter::Paren,
+                        tokens: TokenStream(`""`),
+                    },
+                    semi_token: Some,
+                },
+                Stmt::Expr(
+                    Expr::Macro {
+                        mac: Macro {
+                            path: Path {
+                                segments: [
+                                    PathSegment {
+                                        ident: "vec",
+                                    },
+                                ],
+                            },
+                            delimiter: MacroDelimiter::Bracket,
+                            tokens: TokenStream(``),
+                        },
+                    },
+                    None,
+                ),
+            ],
+        },
+    })
+    "###);
+}
+
+#[test]
+fn test_early_parse_loop() {
+    // The following is an Expr::Loop followed by Expr::Tuple. It is not an
+    // Expr::Call.
+    let tokens = quote! {
+        loop {}
+        ()
+    };
+
+    let stmts = Block::parse_within.parse2(tokens).unwrap();
+
+    snapshot!(stmts, @r###"
+    [
+        Stmt::Expr(
+            Expr::Loop {
+                body: Block {
+                    stmts: [],
+                },
+            },
+            None,
+        ),
+        Stmt::Expr(
+            Expr::Tuple,
+            None,
+        ),
+    ]
+    "###);
+
+    let tokens = quote! {
+        'a: loop {}
+        ()
+    };
+
+    let stmts = Block::parse_within.parse2(tokens).unwrap();
+
+    snapshot!(stmts, @r###"
+    [
+        Stmt::Expr(
+            Expr::Loop {
+                label: Some(Label {
+                    name: Lifetime {
+                        ident: "a",
+                    },
+                }),
+                body: Block {
+                    stmts: [],
+                },
+            },
+            None,
+        ),
+        Stmt::Expr(
+            Expr::Tuple,
+            None,
+        ),
+    ]
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_token_trees.rs b/third_party/rust/syn/tests/test_token_trees.rs
new file mode 100644
index 0000000000..f5a067fd23
--- /dev/null
+++ b/third_party/rust/syn/tests/test_token_trees.rs
@@ -0,0 +1,32 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::Lit;
+
+#[test]
+fn test_struct() {
+    let input = "
+        #[derive(Debug, Clone)]
+        pub struct Item {
+            pub ident: Ident,
+            pub attrs: Vec<Attribute>,
+        }
+    ";
+
+    snapshot!(input as TokenStream, @r###"
+    TokenStream(
+        `# [derive (Debug , Clone)] pub struct Item { pub ident : Ident , pub attrs : Vec < Attribute >, }`,
+    )
+    "###);
+}
+
+#[test]
+fn test_literal_mangling() {
+    let code = "0_4";
+    let parsed: Lit = syn::parse_str(code).unwrap();
+    assert_eq!(code, quote!(#parsed).to_string());
+}
diff --git a/third_party/rust/syn/tests/test_ty.rs b/third_party/rust/syn/tests/test_ty.rs
new file mode 100644
index 0000000000..06453934f8
--- /dev/null
+++ b/third_party/rust/syn/tests/test_ty.rs
@@ -0,0 +1,397 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
+use quote::{quote, ToTokens as _};
+use syn::punctuated::Punctuated;
+use syn::{parse_quote, token, Token, Type, TypeTuple};
+
+#[test]
+fn test_mut_self() {
+    syn::parse_str::<Type>("fn(mut self)").unwrap();
+    syn::parse_str::<Type>("fn(mut self,)").unwrap();
+    syn::parse_str::<Type>("fn(mut self: ())").unwrap();
+    syn::parse_str::<Type>("fn(mut self: ...)").unwrap_err();
+    syn::parse_str::<Type>("fn(mut self: mut self)").unwrap_err();
+    syn::parse_str::<Type>("fn(mut self::T)").unwrap_err();
+}
+
+#[test]
+fn test_macro_variable_type() {
+    // mimics the token stream corresponding to `$ty<T>`
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Group(Group::new(Delimiter::None, quote! { ty })),
+        TokenTree::Punct(Punct::new('<', Spacing::Alone)),
+        TokenTree::Ident(Ident::new("T", Span::call_site())),
+        TokenTree::Punct(Punct::new('>', Spacing::Alone)),
+    ]);
+
+    snapshot!(tokens as Type, @r###"
+    Type::Path {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "ty",
+                    arguments: PathArguments::AngleBracketed {
+                        args: [
+                            GenericArgument::Type(Type::Path {
+                                path: Path {
+                                    segments: [
+                                        PathSegment {
+                                            ident: "T",
+                                        },
+                                    ],
+                                },
+                            }),
+                        ],
+                    },
+                },
+            ],
+        },
+    }
+    "###);
+
+    // mimics the token stream corresponding to `$ty::<T>`
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Group(Group::new(Delimiter::None, quote! { ty })),
+        TokenTree::Punct(Punct::new(':', Spacing::Joint)),
+        TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+        TokenTree::Punct(Punct::new('<', Spacing::Alone)),
+        TokenTree::Ident(Ident::new("T", Span::call_site())),
+        TokenTree::Punct(Punct::new('>', Spacing::Alone)),
+    ]);
+
+    snapshot!(tokens as Type, @r###"
+    Type::Path {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "ty",
+                    arguments: PathArguments::AngleBracketed {
+                        colon2_token: Some,
+                        args: [
+                            GenericArgument::Type(Type::Path {
+                                path: Path {
+                                    segments: [
+                                        PathSegment {
+                                            ident: "T",
+                                        },
+                                    ],
+                                },
+                            }),
+                        ],
+                    },
+                },
+            ],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_group_angle_brackets() {
+    // mimics the token stream corresponding to `Option<$ty>`
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Ident(Ident::new("Option", Span::call_site())),
+        TokenTree::Punct(Punct::new('<', Spacing::Alone)),
+        TokenTree::Group(Group::new(Delimiter::None, quote! { Vec<u8> })),
+        TokenTree::Punct(Punct::new('>', Spacing::Alone)),
+    ]);
+
+    snapshot!(tokens as Type, @r###"
+    Type::Path {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "Option",
+                    arguments: PathArguments::AngleBracketed {
+                        args: [
+                            GenericArgument::Type(Type::Group {
+                                elem: Type::Path {
+                                    path: Path {
+                                        segments: [
+                                            PathSegment {
+                                                ident: "Vec",
+                                                arguments: PathArguments::AngleBracketed {
+                                                    args: [
+                                                        GenericArgument::Type(Type::Path {
+                                                            path: Path {
+                                                                segments: [
+                                                                    PathSegment {
+                                                                        ident: "u8",
+                                                                    },
+                                                                ],
+                                                            },
+                                                        }),
+                                                    ],
+                                                },
+                                            },
+                                        ],
+                                    },
+                                },
+                            }),
+                        ],
+                    },
+                },
+            ],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_group_colons() {
+    // mimics the token stream corresponding to `$ty::Item`
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Group(Group::new(Delimiter::None, quote! { Vec<u8> })),
+        TokenTree::Punct(Punct::new(':', Spacing::Joint)),
+        TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+        TokenTree::Ident(Ident::new("Item", Span::call_site())),
+    ]);
+
+    snapshot!(tokens as Type, @r###"
+    Type::Path {
+        path: Path {
+            segments: [
+                PathSegment {
+                    ident: "Vec",
+                    arguments: PathArguments::AngleBracketed {
+                        args: [
+                            GenericArgument::Type(Type::Path {
+                                path: Path {
+                                    segments: [
+                                        PathSegment {
+                                            ident: "u8",
+                                        },
+                                    ],
+                                },
+                            }),
+                        ],
+                    },
+                },
+                Token![::],
+                PathSegment {
+                    ident: "Item",
+                },
+            ],
+        },
+    }
+    "###);
+
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Group(Group::new(Delimiter::None, quote! { [T] })),
+        TokenTree::Punct(Punct::new(':', Spacing::Joint)),
+        TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+        TokenTree::Ident(Ident::new("Element", Span::call_site())),
+    ]);
+
+    snapshot!(tokens as Type, @r###"
+    Type::Path {
+        qself: Some(QSelf {
+            ty: Type::Slice {
+                elem: Type::Path {
+                    path: Path {
+                        segments: [
+                            PathSegment {
+                                ident: "T",
+                            },
+                        ],
+                    },
+                },
+            },
+            position: 0,
+        }),
+        path: Path {
+            leading_colon: Some,
+            segments: [
+                PathSegment {
+                    ident: "Element",
+                },
+            ],
+        },
+    }
+    "###);
+}
+
+#[test]
+fn test_trait_object() {
+    let tokens = quote!(dyn for<'a> Trait<'a> + 'static);
+    snapshot!(tokens as Type, @r###"
+    Type::TraitObject {
+        dyn_token: Some,
+        bounds: [
+            TypeParamBound::Trait(TraitBound {
+                lifetimes: Some(BoundLifetimes {
+                    lifetimes: [
+                        GenericParam::Lifetime(LifetimeParam {
+                            lifetime: Lifetime {
+                                ident: "a",
+                            },
+                        }),
+                    ],
+                }),
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Trait",
+                            arguments: PathArguments::AngleBracketed {
+                                args: [
+                                    GenericArgument::Lifetime(Lifetime {
+                                        ident: "a",
+                                    }),
+                                ],
+                            },
+                        },
+                    ],
+                },
+            }),
+            Token![+],
+            TypeParamBound::Lifetime {
+                ident: "static",
+            },
+        ],
+    }
+    "###);
+
+    let tokens = quote!(dyn 'a + Trait);
+    snapshot!(tokens as Type, @r###"
+    Type::TraitObject {
+        dyn_token: Some,
+        bounds: [
+            TypeParamBound::Lifetime {
+                ident: "a",
+            },
+            Token![+],
+            TypeParamBound::Trait(TraitBound {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Trait",
+                        },
+                    ],
+                },
+            }),
+        ],
+    }
+    "###);
+
+    // None of the following are valid Rust types.
+    syn::parse_str::<Type>("for<'a> dyn Trait<'a>").unwrap_err();
+    syn::parse_str::<Type>("dyn for<'a> 'a + Trait").unwrap_err();
+}
+
+#[test]
+fn test_trailing_plus() {
+    #[rustfmt::skip]
+    let tokens = quote!(impl Trait +);
+    snapshot!(tokens as Type, @r###"
+    Type::ImplTrait {
+        bounds: [
+            TypeParamBound::Trait(TraitBound {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Trait",
+                        },
+                    ],
+                },
+            }),
+            Token![+],
+        ],
+    }
+    "###);
+
+    #[rustfmt::skip]
+    let tokens = quote!(dyn Trait +);
+    snapshot!(tokens as Type, @r###"
+    Type::TraitObject {
+        dyn_token: Some,
+        bounds: [
+            TypeParamBound::Trait(TraitBound {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Trait",
+                        },
+                    ],
+                },
+            }),
+            Token![+],
+        ],
+    }
+    "###);
+
+    #[rustfmt::skip]
+    let tokens = quote!(Trait +);
+    snapshot!(tokens as Type, @r###"
+    Type::TraitObject {
+        bounds: [
+            TypeParamBound::Trait(TraitBound {
+                path: Path {
+                    segments: [
+                        PathSegment {
+                            ident: "Trait",
+                        },
+                    ],
+                },
+            }),
+            Token![+],
+        ],
+    }
+    "###);
+}
+
+#[test]
+fn test_tuple_comma() {
+    let mut expr = TypeTuple {
+        paren_token: token::Paren::default(),
+        elems: Punctuated::new(),
+    };
+    snapshot!(expr.to_token_stream() as Type, @"Type::Tuple");
+
+    expr.elems.push_value(parse_quote!(_));
+    // Must not parse to Type::Paren
+    snapshot!(expr.to_token_stream() as Type, @r###"
+    Type::Tuple {
+        elems: [
+            Type::Infer,
+            Token![,],
+        ],
+    }
+    "###);
+
+    expr.elems.push_punct(<Token![,]>::default());
+    snapshot!(expr.to_token_stream() as Type, @r###"
+    Type::Tuple {
+        elems: [
+            Type::Infer,
+            Token![,],
+        ],
+    }
+    "###);
+
+    expr.elems.push_value(parse_quote!(_));
+    snapshot!(expr.to_token_stream() as Type, @r###"
+    Type::Tuple {
+        elems: [
+            Type::Infer,
+            Token![,],
+            Type::Infer,
+        ],
+    }
+    "###);
+
+    expr.elems.push_punct(<Token![,]>::default());
+    snapshot!(expr.to_token_stream() as Type, @r###"
+    Type::Tuple {
+        elems: [
+            Type::Infer,
+            Token![,],
+            Type::Infer,
+            Token![,],
+        ],
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/test_visibility.rs b/third_party/rust/syn/tests/test_visibility.rs
new file mode 100644
index 0000000000..496e0070bb
--- /dev/null
+++ b/third_party/rust/syn/tests/test_visibility.rs
@@ -0,0 +1,144 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
+use syn::parse::{Parse, ParseStream};
+use syn::{DeriveInput, Result, Visibility};
+
+#[derive(Debug)]
+struct VisRest {
+    vis: Visibility,
+    rest: TokenStream,
+}
+
+impl Parse for VisRest {
+    fn parse(input: ParseStream) -> Result<Self> {
+        Ok(VisRest {
+            vis: input.parse()?,
+            rest: input.parse()?,
+        })
+    }
+}
+
+macro_rules! assert_vis_parse {
+    ($input:expr, Ok($p:pat)) => {
+        assert_vis_parse!($input, Ok($p) + "");
+    };
+
+    ($input:expr, Ok($p:pat) + $rest:expr) => {
+        let expected = $rest.parse::<TokenStream>().unwrap();
+        let parse: VisRest = syn::parse_str($input).unwrap();
+
+        match parse.vis {
+            $p => {}
+            _ => panic!("Expected {}, got {:?}", stringify!($p), parse.vis),
+        }
+
+        // NOTE: Round-trips through `to_string` to avoid potential whitespace
+        // diffs.
+        assert_eq!(parse.rest.to_string(), expected.to_string());
+    };
+
+    ($input:expr, Err) => {
+        syn::parse2::<VisRest>($input.parse().unwrap()).unwrap_err();
+    };
+}
+
+#[test]
+fn test_pub() {
+    assert_vis_parse!("pub", Ok(Visibility::Public(_)));
+}
+
+#[test]
+fn test_inherited() {
+    assert_vis_parse!("", Ok(Visibility::Inherited));
+}
+
+#[test]
+fn test_in() {
+    assert_vis_parse!("pub(in foo::bar)", Ok(Visibility::Restricted(_)));
+}
+
+#[test]
+fn test_pub_crate() {
+    assert_vis_parse!("pub(crate)", Ok(Visibility::Restricted(_)));
+}
+
+#[test]
+fn test_pub_self() {
+    assert_vis_parse!("pub(self)", Ok(Visibility::Restricted(_)));
+}
+
+#[test]
+fn test_pub_super() {
+    assert_vis_parse!("pub(super)", Ok(Visibility::Restricted(_)));
+}
+
+#[test]
+fn test_missing_in() {
+    assert_vis_parse!("pub(foo::bar)", Ok(Visibility::Public(_)) + "(foo::bar)");
+}
+
+#[test]
+fn test_missing_in_path() {
+    assert_vis_parse!("pub(in)", Err);
+}
+
+#[test]
+fn test_crate_path() {
+    assert_vis_parse!(
+        "pub(crate::A, crate::B)",
+        Ok(Visibility::Public(_)) + "(crate::A, crate::B)"
+    );
+}
+
+#[test]
+fn test_junk_after_in() {
+    assert_vis_parse!("pub(in some::path @@garbage)", Err);
+}
+
+#[test]
+fn test_empty_group_vis() {
+    // mimics `struct S { $vis $field: () }` where $vis is empty
+    let tokens = TokenStream::from_iter(vec![
+        TokenTree::Ident(Ident::new("struct", Span::call_site())),
+        TokenTree::Ident(Ident::new("S", Span::call_site())),
+        TokenTree::Group(Group::new(
+            Delimiter::Brace,
+            TokenStream::from_iter(vec![
+                TokenTree::Group(Group::new(Delimiter::None, TokenStream::new())),
+                TokenTree::Group(Group::new(
+                    Delimiter::None,
+                    TokenStream::from_iter(vec![TokenTree::Ident(Ident::new(
+                        "f",
+                        Span::call_site(),
+                    ))]),
+                )),
+                TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+                TokenTree::Group(Group::new(Delimiter::Parenthesis, TokenStream::new())),
+            ]),
+        )),
+    ]);
+
+    snapshot!(tokens as DeriveInput, @r###"
+    DeriveInput {
+        vis: Visibility::Inherited,
+        ident: "S",
+        generics: Generics,
+        data: Data::Struct {
+            fields: Fields::Named {
+                named: [
+                    Field {
+                        vis: Visibility::Inherited,
+                        ident: Some("f"),
+                        colon_token: Some,
+                        ty: Type::Tuple,
+                    },
+                ],
+            },
+        },
+    }
+    "###);
+}
diff --git a/third_party/rust/syn/tests/zzz_stable.rs b/third_party/rust/syn/tests/zzz_stable.rs
new file mode 100644
index 0000000000..a1a670d9ed
--- /dev/null
+++ b/third_party/rust/syn/tests/zzz_stable.rs
@@ -0,0 +1,33 @@
+#![cfg(syn_disable_nightly_tests)]
+
+use std::io::{self, Write};
+use termcolor::{Color, ColorChoice, ColorSpec, StandardStream, WriteColor};
+
+const MSG: &str = "\
+‖
+‖   WARNING:
+‖   This is not a nightly compiler so not all tests were able to
+‖   run. Syn includes tests that compare Syn's parser against the
+‖   compiler's parser, which requires access to unstable librustc
+‖   data structures and a nightly compiler.
+‖
+";
+
+#[test]
+fn notice() -> io::Result<()> {
+    let header = "WARNING";
+    let index_of_header = MSG.find(header).unwrap();
+    let before = &MSG[..index_of_header];
+    let after = &MSG[index_of_header + header.len()..];
+
+    let mut stderr = StandardStream::stderr(ColorChoice::Auto);
+    stderr.set_color(ColorSpec::new().set_fg(Some(Color::Yellow)))?;
+    write!(&mut stderr, "{}", before)?;
+    stderr.set_color(ColorSpec::new().set_bold(true).set_fg(Some(Color::Yellow)))?;
+    write!(&mut stderr, "{}", header)?;
+    stderr.set_color(ColorSpec::new().set_fg(Some(Color::Yellow)))?;
+    write!(&mut stderr, "{}", after)?;
+    stderr.reset()?;
+
+    Ok(())
+}