SourceFile =
  'shebang'?
  Attr*
  Item*

Item =
  Const
| Enum
| ExternBlock
| ExternCrate
| Fn
| ImplDef
| MacroCall
| Module
| Static
| Struct
| TraitDef
| TypeAlias
| Union
| Use

Module =
  Attr* Visibility? 'mod' Name
  (ItemList | ';')

ItemList =
  '{' Attr* Item* '}'

ExternCrate =
  Attr* Visibility? 'extern' 'crate' (NameRef | 'self') Rename? ';'

Rename =
  'as' (Name | '_')

Use =
  Attr* Visibility? 'use' UseTree ';'

UseTree =
  (Path? '::')? ('*' | UseTreeList )
| Path Rename?

UseTreeList =
  '{' (UseTree (',' UseTree)* ','?)? '}'

Fn =
 Attr* Visibility?
 'default'? ('async' | 'const')? 'unsafe'? Abi?
 'fn' Name GenericParamList? ParamList RetType?
 WhereClause?
 (body:BlockExpr | ';')

Abi =
  'extern' 'string'?

ParamList =
  '('(
    (Param (',' Param)* ','?)?
  | SelfParam ','?
  | SelfParam ',' (Param (',' Param)* ','?)
  )')'

SelfParam =
  Attr* (
    ('&' 'lifetime'?)? 'mut'? 'self'
  | 'mut'? 'self' ':' ascribed_type:TypeRef
  )

Param =
  Attr* (
    Pat (':' ascribed_type:TypeRef)
  | ascribed_type:TypeRef
  | '...'
  )

RetType =
  '->' TypeRef

TypeAlias =
  Attr* Visibility? 'default'? 'type' Name GenericParamList? (':' TypeBoundList?)? WhereClause?
  '=' TypeRef ';'

Struct =
  Attr* Visibility? 'struct' Name GenericParamList? (
    WhereClause?  (RecordFieldList | ';')
  | TupleFieldList WhereClause? ';'
  )

RecordFieldList =
 '{' fields:(RecordField (',' RecordField)* ','?)? '}'

RecordField =
  Attr* Visibility? Name ':' ascribed_type:TypeRef

TupleFieldList =
  '(' fields:(TupleField (',' TupleField)* ','?)? ')'

TupleField =
  Attr* Visibility? TypeRef

FieldList =
  RecordFieldList
| TupleFieldList

Enum =
  Attr* Visibility? 'enum' Name GenericParamList? WhereClause?
  VariantList

VariantList =
 '{' (Variant (',' Variant)* ','?)? '}'

Variant =
  Attr* Visibility? Name FieldList ('=' Expr)?

Union =
  Attr* Visibility? 'union' Name GenericParamList? WhereClause?
  RecordFieldList

Const =
  Attr* Visibility? 'default'? 'const' (Name | '_') ':' ascribed_type:TypeRef
  '=' body:Expr ';'

Static =
  Attr* Visibility? 'static'? 'mut'? Name ':' ascribed_type:TypeRef
  '=' body:Expr ';'

TraitDef =
  Attr* Visibility? 'unsafe'? 'auto'? 'trait' Name GenericParamList
  (':' TypeBoundList?)? WhereClause
  AssocItemList

AssocItemList =
  '{' AssocItem* '}'

ImplDef =
 Attr* Visibility? 'const'? 'default'? 'unsafe'? 'impl' GenericParamList? '!'? 'for'
 WhereClause?
 AssocItemList

ParenType =
  '(' TypeRef ')'

TupleType =
  '(' fields:TypeRef* ')'

NeverType =
  '!'

PathType =
  Path

PointerType =
  '*' ('const' | 'mut') TypeRef

ArrayType =
  '[' TypeRef ';' Expr ']'

SliceType =
  '[' TypeRef ']'

ReferenceType =
  '&' 'lifetime'? 'mut'? TypeRef

PlaceholderType =
   '_'

FnPointerType =
   Abi 'unsafe'? 'fn' ParamList RetType?

ForType =
   'for' GenericParamList TypeRef

ImplTraitType =
  'impl' TypeBoundList

DynTraitType =
  'dyn' TypeBoundList

TupleExpr =
  Attr* '(' Expr* ')'

ArrayExpr =
  Attr* '[' (Expr* | Expr ';' Expr) ']'

ParenExpr =
  Attr* '(' Expr ')'

PathExpr =
  Path

LambdaExpr =
  Attr* 'static'? 'async'? 'move'?  ParamList RetType?
  body:Expr

IfExpr =
  Attr* 'if' Condition

Condition =
  'let' Pat '=' Expr
| Expr

EffectExpr =
  Attr* Label? ('try' | 'unsafe' | 'async') BlockExpr

LoopExpr =
  Attr* Label? 'loop'
  loop_body:BlockExpr?

ForExpr =
  Attr* Label? 'for' Pat 'in' iterable:Expr
  loop_body:BlockExpr?

WhileExpr =
  Attr* Label? 'while' Condition
  loop_body:BlockExpr?

ContinueExpr =
  Attr* 'continue' 'lifetime'?

BreakExpr =
  Attr* 'break' 'lifetime'? Expr?

Label =
  'lifetime'

BlockExpr =
  Attr* Label
  '{'
    Item*
    statements:Stmt*
    Expr?
  '}'

ReturnExpr =
  Attr* 'return' Expr

CallExpr =
  Attr* Expr ArgList

MethodCallExpr =
  Attr* Expr '.' NameRef TypeArgList? ArgList

ArgList =
  '(' args:Expr* ')'

FieldExpr =
  Attr* Expr '.' NameRef

IndexExpr =
  Attr* '[' ']'

AwaitExpr =
  Attr* Expr '.' 'await'

TryExpr =
  Attr* Expr '?'

CastExpr =
  Attr* Expr 'as' TypeRef

RefExpr =
  Attr* '&' ('raw' | 'mut' | 'const') Expr

PrefixExpr =
  Attr* Expr

BoxExpr =
  Attr* 'box' Expr

RangeExpr =
  Attr*

BinExpr =
  Attr*

Literal =
  'int_number'

MatchExpr =
  Attr* 'match' Expr MatchArmList

MatchArmList =
  '{' arms:MatchArm* '}'

MatchArm =
  Attr* Pat guard:MatchGuard? '=>' Expr

MatchGuard =
  'if' Expr

RecordExpr =
 Path RecordExprFieldList

RecordExprFieldList =
  '{'
    fields:RecordExprField*
    ('..' spread:Expr)?
  '}'

RecordExprField =
  Attr* NameRef (':' Expr)?

OrPat =
  Pat*

ParenPat =
  '(' Pat ')'

RefPat =
  '&' 'mut'? Pat

BoxPat =
  'box' Path

BindPat =
  Attr* 'ref'? 'mut'? Name ('@' Pat)?

PlaceholderPat =
  '_'

DotDotPat =
  '..'

PathPat =
  Path

SlicePat =
  '[' args:Pat* ']'

RangePat =
  '..' | '..='

LiteralPat =
  Literal

MacroPat =
  MacroCall

RecordPat =
  Path RecordFieldPatList

RecordFieldPatList =
  '{'
    record_field_pats:RecordFieldPat*
    BindPat*
    '..'?
  '}'

RecordFieldPat =
  Attr* NameRef ':' Pat

TupleStructPat =
   Path '(' args:Pat* ')'

TuplePat =
   '(' args:Pat* ')'

Visibility =
  'pub' ('(' 'super' | 'self' | 'crate' | 'in' Path ')')?

Name =
  'ident'

NameRef =
  'ident' | 'int_number'

MacroCall =
  Attr* Path '!' Name? TokenTree ';'?

MacroDef =
  Name TokenTree

TokenTree =
  '(' ')' | '{' '}' | '[' ']'

MacroItems =
  Item*

MacroStmts =
  statements:Stmt*
  Expr?

Attr =
  '#' '!'? '[' Path ('=' input:AttrInput)? ']'

GenericParamList =
  '<'
    TypeParam*
    LifetimeParam*
    ConstParam*
  '>'

TypeParam =
  Attr* Name (':' TypeBoundList?)?
  ('=' default_type:TypeRef)?

ConstParam =
  Attr* 'const' Name ':' ascribed_type:TypeRef
  ('=' default_val:Expr)?

LifetimeParam =
  Attr* 'lifetime'

TypeBound =
  'lifetime' | 'const'? TypeRef

TypeBoundList =
   bounds:TypeBound*

WherePred =
  ('for' GenericParamList)?  ('lifetime' | TypeRef) ':' TypeBoundList

WhereClause =
  'where' predicates:WherePred*

ExprStmt =
  Attr* Expr ';'

LetStmt =
  Attr* 'let' Pat (':' ascribed_type:TypeRef)
  '=' initializer:Expr ';'

Path =
  (qualifier:Path '::')? segment:PathSegment

PathSegment =
  '::' | 'crate' | 'self' | 'super'
| '<' NameRef TypeArgList ParamList RetType PathType '>'

TypeArgList =
  '::'? '<'
    TypeArg*
    LifetimeArg*
    AssocTypeArg*
    ConstArg*
  '>'

TypeArg =
  TypeRef

AssocTypeArg =
  NameRef (':' TypeBoundList | '=' TypeRef)

LifetimeArg =
  'lifetime'

ConstArg =
  Literal | BlockExpr BlockExpr

ExternBlock =
  Attr* Abi ExternItemList

ExternItemList =
  '{' extern_items:ExternItem* '}'

MetaItem =
  Path '=' AttrInput nested_meta_items:MetaItem*

AdtDef =
  Struct
| Enum
| Union

TypeRef =
  ParenType
| TupleType
| NeverType
| PathType
| PointerType
| ArrayType
| SliceType
| ReferenceType
| PlaceholderType
| FnPointerType
| ForType
| ImplTraitType
| DynTraitType

AssocItem =
  Fn
| TypeAlias
| Const
| MacroCall

ExternItem =
  Fn | Static

AttrInput =
  Literal
| TokenTree

Stmt =
  LetStmt
| ExprStmt

Pat =
  OrPat
| ParenPat
| RefPat
| BoxPat
| BindPat
| PlaceholderPat
| DotDotPat
| PathPat
| RecordPat
| TupleStructPat
| TuplePat
| SlicePat
| RangePat
| LiteralPat
| MacroPat

Expr =
  TupleExpr
| ArrayExpr
| ParenExpr
| PathExpr
| LambdaExpr
| IfExpr
| LoopExpr
| ForExpr
| WhileExpr
| ContinueExpr
| BreakExpr
| Label
| BlockExpr
| ReturnExpr
| MatchExpr
| RecordExpr
| CallExpr
| IndexExpr
| MethodCallExpr
| FieldExpr
| AwaitExpr
| TryExpr
| EffectExpr
| CastExpr
| RefExpr
| PrefixExpr
| RangeExpr
| BinExpr
| Literal
| MacroCall
| BoxExpr