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Anyone know why type checking hates the `val foo: String? by defaultProperty { null }` ? It only goes away by explicitly defining the type of `defaultProperty<String?>`

whoa syntax highlighting in slack? how do you do that?

Unrelated but when you insert the snippet you can select the language

`null` is inferred to be of type `Nothing?` here, so `defaultProperty { null }`  is a `ReadWriteProperty&lt;Any?, Nothing?&gt;`. If you only want a `val` you should use `ReadOnlyProperty`, which has its type parameter marked `out`, in that scenario your code should compile.

<@U589QURRQ> This needs to be both read/write, I have some vars that are mutable. Can I fix `ReadWriteProperty` ’s generics?

In that case you'll have to specify it explicitly. However in the 1.4-M1 blogpost there was a mention about the new type inference improving this situation

If it needs to be a `ReadWriteProperty` then you have to specify the type, otherwise there is no way for the compiler to know that you want a `String?` there.

Seems strange that the type is inferred from the block instead of the `reified T`

You write `defaultProperty { null }`, without specifying the `T` explicitly. So the compiler has to infer it from the arguments to `defaultProperty`, which is just `{ null }`, which is of type `() -&gt; Nothing?` - `T` is therefor inferred to be `Nothing?`

Right, I meant that you would think the type would be inferred from the `val foo: T`

Thats not how type inference works at the moment though, it seems.

But maybe the improvements in 1.4 will fix your use-case

I’m compiling with `-Xnew-inference`  although it doesn’t seem to help.

The improvements are part of 1.4-m1, i think. check out the blogpost