Has anyone built a compiler plugin that gives lamb...

# language-proposals

[Zach Klippenstein (he/him) [MOD]]

Has anyone built a compiler plugin that gives lambdas & anonymous functions more meaningful implementations of `equals`/`hashcode`/`toString`? I work with a lot of code that creates data classes to hold both data and functions (event handlers), and it would be great to actually define lambda equality in a meaningful way. Especially in tests, debugging output, etc. I’ve put some ideas into a twitter thread and as great an excuse as this would be to learn the IR plugin API, would love to just play with someone else’s if it exists.

[ephemient]

React has useCalllback() which wraps a function so that equality is compared based on its dependencies (which also have to be explicitly given)

[ephemient]

in Kotlin, I think something like this would still feel fairly natural,

Model(callback = { foo }.withIdentity(foo))

Untitled

[ephemient]

IMO this is more useful than comparing based on bytecode or source location

[Zach Klippenstein (he/him) [MOD]]

It requires more boilerplate though, and in a huge existing codebase, that’s a non-starter

[ephemient]

the compiler could probably automatically determine what the captured variables are instead of having to pass them by hand... but in a lot of cases the compiler captures this which is more scope than you want or need

[Zach Klippenstein (he/him) [MOD]]

the compiler could probably automatically determine what the captured variables are instead of having to pass them by hand

Isn’t that basically the same thing i was proposing then?

[Zach Klippenstein (he/him) [MOD]]

Or you’re saying it wouldn’t capture this?

[ephemient]

the compiler will capture this if you're using a property, but writing it by hand you can "capture" only the property in use

[Zach Klippenstein (he/him) [MOD]]

ah, i see what you mean