luau/docs/_pages/grammar.md

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/grammar	Grammar	true

chunk ::= {stat [`;']} [laststat [`;']]
block ::= chunk
stat ::= varlist `=' explist |
    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 namelist in explist do block end |
    function funcname funcbody |
    local function Name funcbody |
    local namelist [`=' explist]

laststat ::= return [explist] | break

funcname ::= Name {`.' Name} [`:' Name]
funcbody ::= `(' [parlist] `)' [`:' ReturnType] block end
parlist ::= bindinglist [`,' `...'] | `...'
explist ::= {exp `,'} exp
bindinglist ::= (binding | `...') [`,' bindinglist]

subexpr ::= (asexp | unop subexpr) { binop subexpr }
prefixexp ::= NAME | '(' expr ')'
primaryexp ::= prefixexp { `.' NAME | `[' exp `]' | `:' NAME funcargs | funcargs }
asexp ::= simpleexp [`::' typeannotation]
simpleexp ::= NUMBER | STRING | NIL | true | false | ... | constructor | FUNCTION body | primaryexp
args ::=  `(' [explist] `)' | tableconstructor | String

tableconstructor ::= `{' [fieldlist] `}'
fieldlist ::= field {fieldsep field} [fieldsep]
field ::= `[' exp `]' `=' exp | Name `=' exp | exp
fieldsep ::= `,' | `;'

typeannotation ::=
      nil |
      Name[`.' Name] [`<' namelist `>'] |
     `{' [PropList] `}' |
      `(' [TypeList] `)' `->` ReturnType
      `typeof` typeannotation

typeannotation ::= nil | Name[`.' Name] [ `<' typeannotation [`,' ...] `>' ] | `typeof' `(' expr `)' | `{' [PropList] `}' | [`<' varlist `>'] `(' [TypeList] `)' `->` ReturnType

TypeList ::= TypeAnnotation [`,' TypeList] | ...TypeAnnotation
ReturnType ::= TypeAnnotation | `(' TypeList `)'
TableIndexer ::= `[' TypeAnnotation `]' `:' TypeAnnotation
TableProp ::= Name `:' TypeAnnotation
TablePropOrIndexer ::= TableProp | TableIndexer
PropList ::= TablePropOrIndexer {fieldsep TablePropOrIndexer} [fieldsep]
TableTypeAnnotation ::= `{' PropList `}'
FunctionTypeAnnotation ::= [`<' varlist `>'] `(' [TypeList] `)' `->` ReturnType