TypeParser: variadic arguments are always considered optional #52
 Add this suggestion to a batch that can be applied as a single commit. This suggestion is invalid because no changes were made to the code. Suggestions cannot be applied while the pull request is closed. Suggestions cannot be applied while viewing a subset of changes. Only one suggestion per line can be applied in a batch. Add this suggestion to a batch that can be applied as a single commit. Applying suggestions on deleted lines is not supported. You must change the existing code in this line in order to create a valid suggestion. Outdated suggestions cannot be applied. This suggestion has been applied or marked resolved. Suggestions cannot be applied from pending reviews. Suggestions cannot be applied on multi-line comments. Suggestions cannot be applied while the pull request is queued to merge. Suggestion cannot be applied right now. Please check back later.    
 
this fixes phpstan/phpstan#3798.
it's legal to pass zero arguments to a variadic parameter.
I've ensured that it's still possible to write things like
callable(int ...$foo=) : voidto preserve backwards compatibility, but really it should not be necessary or desirable to add the optional flag to a variadic parameter anyway.