I've rejected this idea in phpstan/phpstan-nette#89 (comment) and that's why I suggested to subtract from MixedType instead.

I've rejected this idea in phpstan/phpstan-nette#89 (comment) and that's why I suggested to subtract from MixedType instead.

ah I see, makes sense. ok then

I always forget that adding more type information / getting rid of mixed will potentially lead to more errors below level 9. I instinctively want to get rid of mixed everywhere :D

@herndlm
https://phpstan.org/r/de94db92-8cac-49f9-bac4-4eb8b7e76ec8
As you mentioned, this case (not related to json_decode) can be solved, but we have to be careful that the union type doesn't contain object related type, because array access on object throws a fatal error.
We can change here

It's just not fixed yet :)

I'll send a pull request for it!

ok sounds interesting, just don't spend too much time on the json_decode case. since mixed or mixed~stdClass is returned it might not work. but that's fine :)

My assumption was not correct...
https://phpstan.org/r/ff9a5441-1529-42a3-b1f6-3b7cb318a7da
While null and string is offsetAccessible. IntegerType, FloatType, BooleanType is not.
This means that we need a little more complicated check in case of $scope->isUndefinedExpressionAllowed($node) === true

so, in case of $scope->isUndefinedExpressionAllowed($node) === true what we have to check is not $isOffsetAccessible->yes() but whether there is a Type that throws a fatal error on offset access even in null-coalesce scope. I will address this issue if more related issues are reported.