Regarding `Kotlin extension functions` VS `future ...

# getting-started

[Edgar Avuzi]

Regarding Kotlin extension functions VS future Java class instance methods. Name collisions

[Edgar Avuzi]

I’ve been thinking about name collisions between extension methods and future instance methods and the potential for silent behavior changes.
Example:

// The code:
fun InputStream.bufferedReader(): BufferedReader = ...

// Usage:
val reader = socket.getInputStream().bufferedReader()

(Imaginary situation)
Later, suppose in JDK Java bufferedReader() instance method will be added to InputStream.java itself:

public BufferedReader bufferedReader() { ... }

When we increment Java version in our project, on recompilation:
• Calling bufferedReader() now uses the new Java instance method instead of my extension method.
• For my extension method there will be compiler warning only like:
This extension is shadowed by a member: 'fun bufferedReader(): BufferedReader' defined in 'java/io/InputStream'.

This seems like a foot gun and bug that can easily slip through when the project codebase gets upgraded to a new Java version.
Having pipeline-style with pipe operator function calls in Kotlin itself (e.g., stream |> bufferedReader) like in Elixir/Gleam languages would avoid that because we would use pipe operator stream |> bufferedReader to mimic extension methods, so there won't be name collisions. That is we would use stream.bufferedReader() for instance methods AND stream |> bufferedReader to mimic extension functions.

Giving today's state of Kotlin :
• How do you handle this risk in your Kotlin codebases?
• Is there a way to have the compiler error on these collisions?

[hfhbd]

This only happens when you recompile your own code with updated dependencies/sdk and you need to always check the new behavior 🤷🏻‍♂️

[hfhbd]

And you can enable warnings as error to fail your build.

[Huib Donkers]

Here's a case where it happened to kotlin https://youtrack.jetbrains.com/issue/KT-67804/removeFirst-and-removeLast-return-type-with-Java-21