Remove empty destructuring

[bbrk24]

Bug report or Feature request?

Feature request

Version (complete output of terser -V or specific git commit)

5.27.2

Complete CLI command or minify() options used

npx terser in.js -o out.js --ecma 13 -f wrap_func_args=false -c unsafe=true,unsafe_arrows=true

terser input

const [,] = m;

terser output or error

const[,]=m;

Expected result

I understand why this can't be done by default, but it would be nice if there were a compress option to remove declarations that don't actually declare anything. This statement is generated by an upstream compiler (Civet 0.6.82, MWE), and in the context of the program I know that the iterator is pure and this statement is safe to drop.

[fabiosantoscode]

I never implemented this because it's not usually safe to do. If m is undefined, that's a TypeError. But of course, it's possible to do if we know it's iterable, or if the user passed some unsafe_xxx option signaling they're okay with being a bit loose with this.

[bbrk24]

Yeah -- as in the linked example code, this only ever happens in my code in a block guarded by Array.isArray(m), so I know it's safe in my case. And I totally understand if it needs to be locked behind an unsafe compress option.