To start off, this is directly from VS Code, I havent tested it anywhere else or in any other way.

VS Code: 1.24.1
Powershell plugin: 1.7.0

A simple statement like this

$collection | %{ $myVar = 0 }{ $myvar += $_}{$myVar}

obviously this is a worthless bit of code, however it complains that myVar is declared but never used.