Hi Guys I have a code like this ```import java security Mess

Question

Hi Guys I have a code like this ```import java security MessageDigest fun foo rp String return bar rp private fun bar rp String ByteArray return MessageDigest getInstance SHA 256 digest rp toByteArray ``` The generarted code for kotlin uses `Intrinsics checkParameterIsNotNull` for `foo` and generates `if rpId ==null ` in `bar` In the later case it throws a `TypeCastException` in case of null and in former an `IllegalArgumentException` So why does generated code need to handle null checks differently

ribesg · Answer

The provided code doesn t even compile

Janar · Answer

``` import java security MessageDigest fun foo rp String return bar rp private fun bar rp String ByteArray return MessageDigest getInstance SHA 256 digest rp toByteArray ```

Janar · Answer

if this because of using inline `String toByteArray ` Even then we could have still used the same null check in `Intrinsics checkParameterIsNotNull rp rp `

diesieben07 · Answer

The difference is between public and private function `foo` is public and therefor can be called from untrusted code including Java who might be passing null In those cases we want `IllegalArgumentException` However `bar` is private and `null` should never end up there If it for some reason does you have done an unchecked cast somewhere in your code

Janar · Answer

< diesieben07> Thanks however when I change the argument in both `foo` and `bar` the null check in bar disappears a primitive byte can be null too ```import java security MessageDigest fun foo rp ByteArray ByteArray return bar rp private fun bar rp ByteArray ByteArray return MessageDigest getInstance SHA 256 digest rp ```

Janar · Answer

decompiled java code for this is ```private static final byte bar byte rp byte var10000 = MessageDigest getInstance SHA 256 digest rp Intrinsics checkExpressionValueIsNotNull var10000 MessageDigest getInstance SHA 256 digest rp return var10000 ```

diesieben07 · Answer

`digest` is a Java method so it s argument is a platform type `ByteArray ` in this case This type is allowed to accept nulls so the compiler does not emit the check

diesieben07 · Answer

Actually I am talking BS

diesieben07 · Answer

You are right the `TypeCastException` is remnants of the `this as java lang String` in `String toByteArray`

Janar · Answer

cool Thanks for clarifying +1

Janar · Answer

just for sake of addition info for archival this thread here captures it well <https github com jacoco jacoco issues 754>

dmitry.petrov · Answer

1 There s some work in progress related to unification of nullability related exceptions However this can potentially change a program behavior and can happen in major release only and we are somewhat late with that change for 1 3 2 Yes currently due to the way redundant null check elimination works in the Kotlin compiler non private functions get somewhat better treatment because they have nullability assertions on parameters and optimizer takes them into account This can be improved in a minor release

Janar · Answer

Thanks < dmitry petrov>

Janar · Answer

My actual motivation for looking in to this behavior was that of code coverage where JaCoCo suddenly started complaining about this piece of code due to inline function being called String toByteArray in this case bringing in the TypeCastException