If I define it using the concrete type `String` doesn’t complaint don’t know why but it works ¯\_(ツ)...

# codereview

[pguardiola]

If I define it using the concrete type String doesn’t complaint don’t know why but it works ¯\_(ツ)_/¯
thanks @anstaendig 👍

[Andreas Sinz]

pguardiola: is that a function type from Java8? i mean is the second generic the return type?

[pguardiola]

Not Java 8

public static <T> PropertyValue<Function<T, String>> lineColor(Function<T, String> function) {
    return new PaintPropertyValue<>("line-color", function);
  }

[Andreas Sinz]

@pguardiola how does Function<I, O> look like?

[pguardiola]

https://github.com/mapbox/mapbox-gl-native/blob/master/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/functions/Function.java

[pguardiola]

It's because of Java's raw types https://stackoverflow.com/a/2770692/1266326

[Andreas Sinz]

@pguardiola It has nothing to do with raw types, its just a mismatch of the Generics. Imagine the follow:

public class Function<I, O> {
    public O getPropertyValue() { }
}

public static <T> PropertyValue<Function<T, String>> lineColor(Function<T, String> function) {
    return new PaintPropertyValue<>("line-color", function);
}

private fun foo(bar: Function<Any, Any>) {
  lineColor(bar)
}

foo(Function<String, Int>())

The lineColor-Method expects your Function<> to return a String on getPropertyValue, but our bar returns an Int.
Passing Function<String, Int> into foo() is perfectly fine, but passing it into lineColor doesn't work because of the different types of O

[pguardiola]

I know but in Java you're able to pass Function (without specifying explicitly the generic types) because of Java's raw types

[Andreas Sinz]

Yeah, kotlin is more restricitve in that matter

[pguardiola]

Yeah because it's 👌implemented 😋