Has anyone figured out how to mimic Rust's dbg! macro with Kotlin? From Rust docs ```fn factorial(n...

# announcements

[pavi2410]

Has anyone figured out how to mimic Rust's dbg! macro with Kotlin?

From Rust docs

fn factorial(n: u32) -> u32 {
  if dbg!(n <= 1) {
    dbg!(1)
  } else {
    dbg!(n * factorial(n - 1))
  }
}

I hope to be able to write something like this in Kotlin

fun factorial(n: Int): Int {
  if (dbg(n <= 1)) {
    return dbg(1)
  } else {
    return dbg(n * factorial (n - 1))
  }
}

Possible incomplete implementation

fun <T> dbg(expr: T): T {
  println(expr)
  return expr
}

Is there any way to capture the expression syntax itself rather than the value?

[pavi2410]

https://kotlinlang.slack.com/archives/C0B9K7EP2/p1547832721116700?thread_ts=1547832721.116700&cid=C0B9K7EP2

Someone suggested using a compiler plugin there

[pavi2410]

I have to write my own compiler plugin to do that. Looks like too much work, but it would be fun nonetheless!

https://resources.jetbrains.com/storage/products/kotlinconf2018/slides/5_Writing%20Your%20First%20Kotlin%20Compiler%20Plugin.pdf

[Dominaezzz]

There's an existing compiler plugin that does a very similar thing. I think it's called Kotlin power assert.

[Youssef Shoaib [MOD]]

yep it's com.bnorm.power.kotlin-power-assert : https://github.com/bnorm/kotlin-power-assert

[itnoles]

is that is very similar of check function?

[christophsturm]

i have written a library that could be helpful but its only meant for test sources. https://github.com/christophsturm/filepeek