According to the tokenize function of JS,

const regex = /\s*(->|[-+*/\(\)\[\]\{\};,]|[A-Za-z]+|[0-9]+)\s*/g;

it will generate something like {_, but it should be { and _.
The correct regex should be

const regex = /\s*(->|[-+*/\(\)\[\]\{\};,]|[A-Za-z_]+|[0-9]+)\s*/g;

the key is [A-Za-z_].

According to the BNF (which is NOT a valid Kotlin BNF)，

function ::= expression "(" [parameters] ")" [lambda]
           | expression lambda

expression ::= nameOrNumber
             | lambda

lambda ::= "{" [lambdaparam "->"] [lambdastmt] "}"

the program {}{}{} is valid. Just pick lambda of expression and expression lambda of function, we can construct a infinite lambda list.

Modify the BNF, or remove this test.