Source: Luau.org · MIT · View source Imported 2026-10-03. Formatting adapted for this site.
Syntax Grammar
This is the complete syntax grammar for Luau in EBNF. More information about the terminal nodes STRING and NUMBER is available in the syntax section.
chunk ::= block
block ::= {stat [';']} [laststat [';']]
stat ::= varlist '=' explist |
var compoundop exp |
functioncall |
'do' block 'end' |
'while' exp 'do' block 'end' |
'repeat' block 'until' exp |
'if' exp 'then' block {'elseif' exp 'then' block} ['else' block] 'end' |
'for' binding '=' exp ',' exp [',' exp] 'do' block 'end' |
'for' bindinglist 'in' explist 'do' block 'end' |
attributes 'function' funcname funcbody |
attributes 'local' 'function' NAME funcbody |
'local' bindinglist ['=' explist] |
'const' 'function' NAME funcbody |
'const' bindinglist '=' explist |
['export'] 'type' NAME ['<' GenericTypeListWithDefaults '>'] '=' Type |
['export'] 'type' 'function' NAME funcbody
laststat ::= 'return' [explist] | 'break' | 'continue'
funcname ::= NAME {'.' NAME} [':' NAME]
funcbody ::= ['<' GenericTypeList '>'] '(' [parlist] ')' [':' ReturnType] block 'end'
parlist ::= bindinglist [',' '...' [':' (GenericTypePack | Type)]] | '...' [':' (GenericTypePack | Type)]
explist ::= {exp ','} exp
binding ::= NAME [':' Type]
bindinglist ::= binding [',' bindinglist] (* equivalent of Lua 5.1 'namelist', except with optional type annotations *)
var ::= NAME | prefixexp '[' exp ']' | prefixexp '.' NAME
varlist ::= var {',' var}
prefixexp ::= var | functioncall | '(' exp ')'
functioncall ::= prefixexp funcargs | prefixexp ':' NAME funcargs
exp ::= asexp { binop exp } | unop exp { binop exp }
ifelseexp ::= 'if' exp 'then' exp {'elseif' exp 'then' exp} 'else' exp
asexp ::= simpleexp ['::' Type]
stringinterp ::= INTERP_BEGIN exp { INTERP_MID exp } INTERP_END
simpleexp ::= NUMBER | STRING | 'nil' | 'true' | 'false' | '...' | tableconstructor | attributes 'function' funcbody | prefixexp | ifelseexp | stringinterp
funcargs ::= '(' [explist] ')' | tableconstructor | STRING
tableconstructor ::= '{' [fieldlist] '}'
fieldlist ::= field {fieldsep field} [fieldsep]
field ::= '[' exp ']' '=' exp | NAME '=' exp | exp
fieldsep ::= ',' | ';'
compoundop ::= '+=' | '-=' | '*=' | '/=' | '//=' | '%=' | '^=' | '..='
binop ::= '+' | '-' | '*' | '/' | '//' | '^' | '%' | '..' | '<' | '<=' | '>' | '>=' | '==' | '~=' | 'and' | 'or'
unop ::= '-' | 'not' | '#'
littable ::= '{' [litfieldlist] '}'
litfieldlist ::= litfield {fieldsep litfield} [fieldsep]
litfield ::= [NAME '='] literal
literal ::= 'nil' | 'false' | 'true' | NUMBER | STRING | littable
litlist ::= literal {',' literal}
pars ::= '(' [litlist] ')' | littable | STRING
parattr ::= NAME [pars]
attribute ::= '@' NAME | '@[' parattr {',' parattr} ']'
attributes ::= {attribute}
SimpleType ::=
'nil' |
SingletonType |
NAME ['.' NAME] [ '<' [TypeParams] '>' ] |
'typeof' '(' exp ')' |
TableType |
FunctionType |
'(' Type ')'
SingletonType ::= STRING | 'true' | 'false'
Union ::= [SimpleType {'?'}] {'|' SimpleType {'?'}}
Intersection ::= [SimpleType] {'&' SimpleType}
Type ::= Union | Intersection
GenericTypePackParameter ::= NAME '...'
GenericTypeList ::= NAME [',' GenericTypeList] | GenericTypePackParameter {',' GenericTypePackParameter}
GenericTypePackParameterWithDefault ::= NAME '...' '=' (TypePack | VariadicTypePack | GenericTypePack)
GenericTypeListWithDefaults ::=
NAME ['=' Type] [',' GenericTypeListWithDefaults] |
GenericTypePackParameterWithDefault {',' GenericTypePackParameterWithDefault}
TypeList ::= Type [',' TypeList] | '...' Type
BoundTypeList ::= [NAME ':'] Type [',' BoundTypeList] | GenericTypePack | VariadicTypePack
TypeParams ::= (Type | TypePack | VariadicTypePack | GenericTypePack) [',' TypeParams]
TypePack ::= '(' [TypeList] ')'
GenericTypePack ::= NAME '...'
VariadicTypePack ::= '...' Type
ReturnType ::= Type | TypePack | GenericTypePack | VariadicTypePack
TableIndexer ::= ['read' | 'write'] '[' Type ']' ':' Type
TableProp ::= ['read' | 'write'] NAME ':' Type
PropList ::= TableProp [fieldsep PropList] | TableIndexer {fieldsep TableProp}
TableType ::= '{' Type '}' | '{' [PropList] '}'
FunctionType ::= ['<' GenericTypeList '>'] '(' [BoundTypeList] ')' '->' ReturnType