https://trycf.com/gist/40e48c92a45cb69052612527f5136ba5/lucee5?theme=monokai

["tahi", "rua", "toru", "wha"].each((v, i) => {
    writeOutput("#i#:#v#<br>")
})

[true, false].each((v, i) => {
    writeOutput("#i#:#v#<br>")
})

Errors with "Invalid Syntax Closing []] not found on line 6" stick a semi-colon after the first expression: all good. Will check Jira...

there's only 103 tickets tagged syntax https://luceeserver.atlassian.net/issues/?jql=labels%20%3D%20%22syntax%22

Is it fixable? It's almost (but not quite) ambiguous code. Because without the semi, its almost not clear if you are trying to define a new array, or reference the previous one. https://trycf.com/gist/e0c70dddc0b3672fd2bb6fa9d166c94f/lucee5?theme=monokai In the exact case, with [true, false] its less ambiguous, but could it be fixed in the case I outlined without breaking other expected functionality?

Yeah suspect it's thinking I have written this:

["tahi", "rua", "toru", "wha"].each((v, i) => {
    writeOutput("#i#:#v#<br>")
})[true, false]

As in it's thinking the

[true, false]

thing is badly-formed associative array notation.