Kotlin, smart cast is impossible because of complex expression

I have this code:

// allocate one mesh
pScene.mNumMeshes = 1
pScene.mMeshes = mutableListOf(AiMesh())
val pMesh = pScene.mMeshes[0]

Where `mMeshes` is a parameter of type

`var mMeshes: MutableList<AiMesh>? = null,`

Compilers complains on the last row, where I try to declare `pMesh`

> Smart cast to `MutableList<AiMesh>` is impossible because `pScene.mMeshes` is a complex expression

What's the problem?

Since `mMeshes` is a `var` property, it can change between the assignment of `mutableListOf(AiMesh())` and the usage in `pScene.mMeshes[0]`, meaning that it is not guaranteed to be not-null at the use site.

The compiler enforces [null-safety][1], treating `pScene.mMeshes` as nullable `MutableList<AiMesh>?` and not allowing you to use it as `MutableList<AiMesh>` (i.e. it cannot safely perform a [smart cast][2]).

To fix that, you can simply make a [non-null assertion][3]:

val pMesh = pScene.mMeshes!![0]

Or just reuse the value you put into the list:

val pMesh = AiMesh()
pScene.mMeshes = mutableListOf(mesh)
// use `pMesh` below


[1]:

[To see links please register here]

[2]:

[To see links please register here]

[3]:

[To see links please register here]