I saw this mentioned in another channel but not di...

# language-proposals

[Ben Dodson]

I saw this mentioned in another channel but not discussed here-- Lambdas that disallow capture. Use {{}} instead of `{}`: chain.map{{ input -> /* capture throws a compiler error */ }}

[elizarov]

What is your use-case for this feature?

[Ben Dodson]

My apologies. Use-case is to avoid leaks from lambdas, and minimize number of generated classes

[Dico]

If you want to explicitly avoid capturing, use a function reference that isn't bounded to any local variable

[Dominaezzz]

Would also be useful for Native? Instead of the whole @VolatileLambda thing.

[Ben Dodson]

we typically do use a function reference, but it isn’t as convenient as inlining a single-use lambda

[elizarov]

Why this should be a language feature? Are you looking, maybe, for an IDE inspection/highlight that brings attention to captured values?

[elizarov]

I mean, I don’t see how it adds to the language.

[Ben Dodson]

Yes-- it would enable IDE highlighting (errors in {{}} where there may be warnings in {}), lint rules, guaranteed compiler optimizations

[louiscad]

I personally set my code scheme to underline with purple green dots captured values, so I'm always aware of that.

[voddan]

guaranteed compiler optimizations

That's already there

[Peter Laggner]

Proposed something similar in March - allowing lambdas to capture weakly as swift does with [weak self] (however from my private and not my work account)