Suppose I have the following code, where `x` is an...

# language-proposals

[Derek Peirce]

Suppose I have the following code, where x is an `Int`:

val y = x.takeIf { it > 5 } ?: 3

The compiled bytecode becomes:

Integer var2 = x;
int it = ((Number)var2).intValue();
int y = (it > 5 ? var2 : null) != null ? it > 5 ? var2 : null : 3;

This has some undesirable boxing and unboxing, it would be ideal if the compiler could optimize this to the equivalent of:

val y = if (x > 5) x else 3

which compiles in Java to:

int y = x > 5 ? x : 3;

What makes this particularly desirable? Consider the protobuf pattern: https://developers.google.com/protocol-buffers/docs/javatutorial#the-protocol-buffer-api

public boolean hasId();
public int getId();

To avoid boxing, primitives are stored with a default value, and a bitfield to indicate which primitives are truly set. Otherwise, we would ideally have a single method:

inline fun getId(): Int? = if (hasId()) getPrimitiveId() else null

It is inlined so that any boxing elimination could be carried out across method calls. If the compiler could eliminate unnecessary boxing, then this call:

if (proto.hasId()) proto.getId() else calculateDefault()

could be replaced with the more straightforward:

proto.getId()?: calculateDefault()

[Fleshgrinder]

Protobuf never gives you null and has no has method for scalar types (they had in Proto2 if I recall correctly). That said, you're request makes perfect sense. I think there is a lot of room to improve the compiler output.

[Derek Peirce]

This is a use case in which, if boxing could be optimized out, Proto would be able to use null in place of requiring has followed by get. From my link, you can see the hasId method, what does would it have in Proto3?

[Fleshgrinder]

In Proto3 scalar values always have a default and optional and required do not exist anymore. An int32 always gives you 0 if it was not set. You have to use a message if you want to know if it is present or not.