Luau typechecker incorrectly declares values as never and *blocked*

[ellienonekomimi (ellie)]

Scripts I wrote last week are not taken kindly to by the luau typechecker when using the --!strict directive. I see types that were previously resolved just fine now assigned *blocked* typing or even never typing for some reason. I have attached a sample place file of a util module which suffers from the incorrect typechecking.

A private message is associated with this bug report

[Yuria_theWitch]

Thanks for the report! For an immediate resolution, you can disable the New Type Solver beta feature, and neither of these issues will occur.

The never types are a duplicate of this issue, where I gave a thorough response explaining the source of the bug. I am working on a solution for it, but can’t make any promises to when it will be resolved:

Variables are type "never" in an if statement

Thanks for the report! It is definitely a bug that the type of script.Parent gets refined to never in this case. It has nothing to do with defaulting to never though, and aroloxia is unfortunately mistaken about what never means. never is a type that represents impossibility, i.e. it’s a type that cannot be constructed in any way. For a legitimate instance of this, consider the builtin function error. No matter what you pass to error, calling the function will never return, so we consider error …

The other bit, the blocked types, are also a known issue where type inference is not able to complete because the set of dependencies between constraints is over-specified. We have a big project well under way in the New Type Solver to avoid getting into these unresolvable situations with over-specified dependencies.