GDScript: Disallow strings as comments

[HolonProduction]

What problem(s) does this PR solve?

• Fixes Dangling quoted lines does not generate a warning or error. #84777
• Closes GDScript: Phase out string literals as multiline comments godot-proposals#15279

Additional information

GDScript does allow string literals as multiline comments to some extends. E.g. they are excepted in a top level context, in contrast to other literals.

Note: This PR does not break compat. Using string literals at the top level is still accepted. What this PR does, is making string literals subject to "standalone expression" warnings.

This was introduced for 4.x with #72971. I think it made sense at the time, since it was in 3.x.

However it did surprise me that this was an (supposedly) intended thing, because:

• the sentiment I've gathered during my time on the project from multiple people, was that this is a python thing and we should use comments in GDScript (see e.g. Very inconsistent comment stripping from release exports #112523 (comment), https://forum.godotengine.org/t/how-to-write-multiline-comments/33257, https://forum.godotengine.org/t/commenting-code/58366, Multi line comments in GDScript #21310 (comment))
• It is not mentioned at all in the comment section of the GDScript reference.
• The literal section of the reference also makes no mention of it.
• I have it on safe authorithy that this does not exist /s

All of this might be case for documentation. tl;dr However as outlined in #112523 the comment stripping that is offered by binary tokenization does not apply to string literals, so encouraging users to do this is a footgun. As such I think we should phase out this feature during 4.x.

In a scope context there is simply no good way to tell apart a user error and a "multi-line comment". And I'd rather warn users than keep an undocumented feature.

Note

I don't know how controversial this is. So if necessary I can open a proposal about it.

[Mickeon]

I would love this, but let me tell you right off the bat: this is most definitely going to be controversial and indeed it warrants a proposal, with the same sentiments brought up here.

If it were just up to me, I would still accept this and gather public feedback, personally.
Mainly to protect beginners. But also, by disabling the warning you acknowledge to be doing something unexpected or unconventional, which especially nowadays a "strings as comments" very much is.

"Nowadays", because using them may make even less sense with the general improvements made to the editor:

• Toggling comments doesn't work the same as 4.0 and is overall regarded as more comfortable.
• Words such as "TODO" are highlighted in comments
• Documentation comments are highlighted more distinctly.
• I was looking for Autofill comment when inserting a new line in documentation #95955 but I discovered that it wasn't merged at all. If it did, it would've made writing "multiline" comments more comfortable, and further justify removing this.

[HolonProduction]

Alright I opened a proposal about it: godotengine/godot-proposals#15279

Putting in draft for the time being.

[HolonProduction]

I'm not seeing any pushback on the proposal, so I'd say this is ready for review.

[Ivorforce]

I approve of the change - standalone strings have no use-case for us and we should lean in to comments for documentation. Implementation wise I think this is the perfect way to handle it: Backwards compat kept but adding warnings.

Code looks good to me.

[Repiteo]

Thanks!