Fix #9634: Cannot use "T is never" in conditional return

[phpstan-bot]

Summary

When using (T is never ? false : bool) as a conditional return type on a generic interface method, PHPStan incorrectly reported "Condition 'T is never' in conditional return type is always false." The fix allows never to correctly recognize that a template type T might be instantiated to never.

Changes

• Added TemplateType handling in src/Type/NonAcceptingNeverType.php — isSuperTypeOf() now returns Maybe for template types instead of No
• Added the same TemplateType handling in src/Type/NeverType.php for consistency
• New rule test in tests/PHPStan/Rules/PhpDoc/data/bug-9634.php and test method in tests/PHPStan/Rules/PhpDoc/MethodConditionalReturnTypeRuleTest.php
• New type inference test in tests/PHPStan/Analyser/nsrt/bug-9634.php verifying that Option<never>::isSome() resolves to false and Option<int>::isSome() resolves to bool

Root cause

NonAcceptingNeverType::isSuperTypeOf() (the type used for explicitly written never in PHPDoc) returned No for all types except NeverType and NonAcceptingNeverType. When ConditionalReturnTypeRuleHelper checked whether the condition T is never could ever be true by calling $targetType->isSuperTypeOf($subjectType), the never target returned No for the template type T, causing the rule to report the condition as "always false". However, a template type T can be instantiated to never (since never is a subtype of any bound), so the correct answer is Maybe.

Test

• Rule test verifies that (T is never ? false : bool) no longer produces a false positive error
• NSRT test verifies that when T is bound to never, the conditional resolves to false, and when T is bound to int, it resolves to bool

Fixes phpstan/phpstan#9634