Some misunderstanding of type infer ```private fun getFile(name: String) { val file = fopen(...

# kotlin-native

[rjhdby]

Some misunderstanding of type infer

private fun getFile(name: String) {
        val file = fopen(name, "wt")
        if (file == null) throw Error("Cannot write file '$name'")
        return file

private fun writeM4() {
        val file = getFile("config.m4")
        fputs(m4Content, file)
...
    }

Compiler is fail with errors

dsl.kt:77:30: error: type mismatch: inferred type is Unit but CValuesRef<FILE /* = _IO_FILE */>? was expected
            fputs(m4Content, file)
                             ^
dsl.kt:86:16: error: type mismatch: inferred type is CPointer<FILE /* = _IO_FILE */>? but Unit was expected
        return file

Why it does not infer automatically?

[russhwolf]

Add the return type to getFile(). Return type always needs to be explicit in a function with a block body.

[olonho]

Sure, your getFile signature assumes Unit return type, make it return FILE

[rjhdby]

In JVM Kotlin return type inferred automatically. Nikolay, may be you know, JetBrains have plans to add this behavior?

[olonho]

it is inferred automatically in both Kotlin/JVM and Kotlin/Native, your code just explicitly says (by omitting return type) that it returns Unit: https://kotlinlang.org/docs/reference/functions.html#unit-returning-functions

[rjhdby]

Indeed, I'm sorry