Denis Zharkov
406e31f54a
Mostly this commit is about skipping wildcards that are redundant in some sense.
The motivation is that they looks `long` in Java code.
There are basically two important parts: return types and value parameters.
1. For return types default behaviour is skipping all declaration-site wildcards.
The intuition behind this rule is simple: return types are basically used in subtype position
(as an argument for another call), and here everything works well in case of 'out'-variance.
For example we have 'Out<Out<T>>>' as subtype both for 'Out<Out<T>>>' and 'Out<? extends Out<? extends T>>>',
so values of such type is more flexible in contrast to `Out<? extends Out<? extends T>>>` that could be used only
for the second case.
But we have choosen to treat `in`-variance in a different way: argument itself
should be rendered without wildcard while nested arguments are rendered by the rules
described further (see second part).
For example: 'In<Out<OpenClass>>' will have generic signature 'In<Out<? extends OpenClass>>'.
If we omit all wildcards here, then value of type 'In<Out<OpenClass>>'
will be impossible to use as argument for function expecting 'In<? super Out<? extends Derived>>'
where Derived <: OpenClass (you can check it manually :]).
And this exception should not be very inconvinient because in-variance is rather rare.
2. For value parameters we decided to skip wildcards if it doesn't make obtained signature weaker
in a sense of set of acceptable arguments.
More precisely:
a. We write wildcard for 'Out<T>' iff T ``can have subtypes ignoring nullability''
b. We write wildcard for 'In<T>' iff T is not equal to it's class upper bound (ignoring nullability again)
Definition of ``can have subtypes ignoring nullability'' is straightforward and you can see it in commit.
#KT-9801 Fixed
#KT-9890 Fixed
24 lines
602 B
Kotlin
Vendored
24 lines
602 B
Kotlin
Vendored
class Inv<E>
|
|
class Out<out T>
|
|
class OutPair<out Final, out Y>
|
|
class In<in Z>
|
|
|
|
class Final
|
|
open class Open
|
|
|
|
fun arrayOfOutOpen(x: Array<Out<Open>>) {}
|
|
// method: ArraysKt::arrayOfOutOpen
|
|
// generic signature: ([LOut<+LOpen;>;)V
|
|
|
|
fun arrayOfOutFinal(x: Array<Out<Final>>) {}
|
|
// method: ArraysKt::arrayOfOutFinal
|
|
// generic signature: ([LOut<LFinal;>;)V
|
|
|
|
fun outOfArrayOpen(x: Out<Array<Open>>) {}
|
|
// method: ArraysKt::outOfArrayOpen
|
|
// generic signature: (LOut<[LOpen;>;)V
|
|
|
|
fun outOfArrayOutOpen(x: Out<Array<out Open>>) {}
|
|
// method: ArraysKt::outOfArrayOutOpen
|
|
// generic signature: (LOut<+[LOpen;>;)V
|