what you guys think about nullable parameters defa...

# language-proposals

[gabrielfv]

what you guys think about nullable parameters defaulting to null? fun foo(bar: Int?) can be called like foo(), instead of having to write fun foo(bar: Int? = null). I see people comonly reading the ? as sort of "opitional" in this context, and I don't see the point of calling foo(null), though makes some sense when

val a: Int? = mayReturnInt()
foo(a)

which is also a common scenario

[umar]

There are few cases you really need nullable types, so being explicit achieves two goals: you can see that here is default argument and it is null, and code will be consistent for nullable and nonnullable types.

[gabrielfv]

I see those cases. I see that there would be consistence between types given that when they have the ? operator they could be null by default, and there'd be no other possibility for a default value, unlike 0 for Int or "" for String.

[gabrielfv]

Having types not null by default and depending on an attention raising operator like ? makes it very clear that a value can be null. That's it's role after all.

[gabrielfv]

It also doesn't break consistency with non-null parameters, since fun foo(a: Int? = 0) can accept foo(null), with a actually being null and foo() with a being 0.

[gabrielfv]

The other side, the scenario where fun foo(bar: Int) would not be passive of being called foo() and would break is not a different behavior, but could be due to the fact that bar could not be null and therefore there is no way to infer anything.

[benleggiero]

Too confusing. Looks like ? means "optional parameter", not "nullable and optional". I can imagine newcomers thinking that Kotlin only allows omitted optional parameters to be null and not bothering to discover the = syntax

[benleggiero]

This would also break any APIs where the designer wanted the developer to be explicit about whether something's null

[gabrielfv]

I don't see what you mean in this last message, @benleggiero

[gabrielfv]

APIs that wanted the user to call a method like foo(null) explicitly? Is there any example?

[umar]

Can you get with use case, where you need so many `nullable`s, and their default must be null?