Inline for property accessors

Feedback

Discussion of this proposal is held in this issue.

Support inline modifier for properties that don't have a backing field and accessors of such properties.

Enable @InlineOnly properties whose signatures can be changed without affecting the binary compatiblity of a library
Make reified type parameters available for property accessors

We propose to allow the inline modifier on properties that do not have a backing field.

It may be used on the sole accessor of a val:

val foo: Foo
    inline get() = Foo()

Or one or both accessors of a var:

var bar: Bar
    inline get() = ...
    inline set(v) { ... }

At the call site the accessors are inlined as normal functions.

The inline modifier may also be used on the property itself:

inline var bar: Bar
    get() = ...
    set(v) { ... }

In such a case, all accessors are marked inline automatically.

Applying inline to a property that has a backing field, or its accessor, results in a compile-time error.