golang词法BNF

golang词法BNF如下：

SourceFile       = PackageClause ";" { ImportDecl ";" } { TopLevelDecl ";" } .
PackageClause    = "package" PackageName .
PackageName      = identifier .
ImportDecl       = "import" ( ImportSpec | "(" { ImportSpec ";" } ")" ) .
ImportSpec       = [ "." | PackageName ] ImportPath .
ImportPath       = string_lit .
TopLevelDecl     = Declaration | FunctionDecl | MethodDecl .
Declaration      = ConstDecl | TypeDecl | VarDecl .
ConstDecl        = "const" ( ConstSpec | "(" { ConstSpec ";" } ")" ) .
ConstSpec        = IdentifierList [ [ Type ] "=" ExpressionList ] .
IdentifierList   = identifier { "," identifier } .
ExpressionList   = Expression { "," Expression } .
TypeDecl         = "type" ( TypeSpec | "(" { TypeSpec ";" } ")" ) .
TypeSpec         = identifier Type .
Type             = TypeName | TypeLit | "(" Type ")" | "*" Type | ArrayType | StructType | PointerType | FunctionType | InterfaceType | SliceType | MapType | ChannelType .
TypeName         = identifier .
TypeLit          = ArrayType | StructType | PointerType | FunctionType | InterfaceType | SliceType | MapType | ChannelType .
ArrayType        = "[" ArrayLength "]" ElementType .
ArrayLength      = Expression .
ElementType      = Type .
StructType       = "struct" "{" { FieldDecl ";" } "}" .
FieldDecl        = ( IdentifierList Type | EmbeddedField ) [ Tag ] .
EmbeddedField    = [ "*" ] TypeName .
Tag              = string_lit .
PointerType      = "*" BaseType .
BaseType         = Type .
FunctionType     = "func" Signature .
Signature        = Parameters [ Result ] .
Result           = Parameters | Type .
Parameters       = "(" [ ParameterList [ "," ] ] ")" .
ParameterList    = ParameterDecl { "," ParameterDecl } .
ParameterDecl    = [ IdentifierList ] [ "..." ] Type .
InterfaceType    = "interface" "{" { MethodSpec ";" } "}" .
MethodSpec       = MethodName Signature | InterfaceTypeName .
MethodName       = identifier .
InterfaceTypeName = TypeName .
SliceType        = "[" "]" ElementType .
MapType          = "map" "[" KeyType "]" ElementType .
KeyType          = Type .
ChannelType      = ( "chan" [ "<-" ] | "<-" "chan" ) ElementType .
VarDecl          = "var" ( VarSpec | "(" { VarSpec ";" } ")" ) .
VarSpec          = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) .
Expression       = UnaryExpr | Expression binary_op Expression .
UnaryExpr        = PrimaryExpr | unary_op UnaryExpr .
PrimaryExpr      = Operand | Conversion | "(" Expression ")" | PrimaryExpr Selector | PrimaryExpr Index | PrimaryExpr Slice | PrimaryExpr TypeAssertion | PrimaryExpr Arguments .
Operand          = Literal | OperandName | MethodExpr | "(" Expression ")" .
Literal          = BasicLit | CompositeLit | FunctionLit .
BasicLit         = int_lit | float_lit | imaginary_lit | rune_lit | string_lit .
OperandName      = identifier | QualifiedIdent.
QualifiedIdent   = PackageName "." identifier .
MethodExpr       = ReceiverType "." MethodName .
ReceiverType     = Type .
Index            = "[" Expression "]" .
Slice            = "[" [ Expression ] ":" [ Expression ] "]" | "[" [ Expression ] ":" Expression ":" Expression "]" .
Arguments        = "(" [ ( ExpressionList | Type [ "," ExpressionList ] ) [ "..." ] ] ")" .
CompositeLit     = LiteralType LiteralValue .
LiteralType      = StructType | ArrayType | "[" "..." "]" ElementType | SliceType | TypeName .
LiteralValue     = "{" [ ElementList [ "," ] ] "}" .
ElementList      = KeyedElement { "," KeyedElement } .
KeyedElement     = [ Key ":" ] Element .
Key              = FieldName | Expression | LiteralValue .
FieldName        = identifier .
Conversion       = Type "(" Expression [ "," ] ")" .