I think I might have found a bug in the Compose co...

# compose

[Trevor Stone]

I think I might have found a bug in the Compose compiler. If you have an interface that defines Composable functions, you cannot use default values without it crashing. I’ll put full code examples in the thread

interface Foo {
    //This will crash if overridden and called with the default value
    @Composable
    fun Bar(modifier: Modifier = Modifier) {
    }
}

[Trevor Stone]

Impl

class FooBar : Foo {
    @Composable
    override fun Bar(modifier: Modifier) {
        println("$modifier")
    }
}


interface Foo {
    //This will crash if overridden and called with the default value
    @Composable
    fun Bar(modifier: Modifier = Modifier) {
    }
}

[Trevor Stone]

Crash is:

java.lang.NullPointerException: Parameter specified as non-null is null: method com.example.myapplication.FooBar.Bar, parameter modifier
                                                                                                    	at com.example.myapplication.FooBar.Bar(Unknown Source:2)

[Trevor Stone]

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val fooBar = FooBar()
        setContent {
            fooBar.Bar()
        }
    }
}

How it’s called

[Trevor Stone]

If I make them not Composable functions it works without crashing

[jw]

File a bug. The compiler should never crash.

[Trevor Stone]

This does crash at runtime and not compile-time

[Ben Trengrove [G]]

Definitely a compiler bug, can you please file an issue? https://goo.gle/compose-feedback

[Ben Trengrove [G]]

I should add as well, default values in composable interface functions are currently not supported. The compiler should be picking that up at compile time though, not runtime.

[Trevor Stone]

Thanks! https://issuetracker.google.com/issues/317490247