PSUseDeclaredVarsMoreThanAssignments is not aware of the scriptblock context (invocation or dot-sourcing)

Steps to reproduce

Extracted from here but similar issues also reported in #711

It’s a PSSA bug. I get the same warning with:

$totalSize = 0
. { $totalSize += 1 }
$totalSize

PSSA is apparently analyzing each script block independently.

It needs to recognize when a script block is dot sourced and analyze it in the context of where it is >invoked. This isn’t always possible, but it’s usually easy to do when using ForEach-Object (which dot >sources like this).

In trying some variants on the idea, it seems like there are multiple bugs:

$totalSize = 0
function foo {
$x = $totalSize + 1
$totalSize = $x # Should warn, doesn't (bug)
}
& {
$x = $totalSize + 1
$totalSize = $x # Should warn, doesn't (bug)
}
. {
$x = $totalSize + 1
$totalSize = $x # Should not warn, doesn't (no bug)
}
. {
$totalSize += 1 # Should not warn, does (bug)
}
$totalSize

PSUseDeclaredVarsMoreThanAssignments の実装を起点にし、issue にある invocation、dot-sourcing、function、scriptblock の例を再現してください。各診断をコメントに記載された期待される動作と比較してください。analyzer がこれらのコンテキストを誤検出や警告漏れなしに処理できれば完了です。