[4.1] Validate class constraints for generic arguments of types #14178
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…pes. Class constraints (spelled T: AnyObject) on generic types were not getting checked on generic arguments. This appears to be a regression introduced in Swift 4.0 with the removal of AnyObject, leading to a fairly significant soundness hole that could produce crashers later on. Fixes SR-6841 / rdar://problem/36884025. (cherry picked from commit ee99c8a)
(cherry picked from commit 4672c11)
(cherry picked from commit 4050799)
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@swift-ci please test |
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@swift-ci please nominate |
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• Explanation:
AnyObjectconstraints on type parameters of generic types weren't getting checked, allowing invalid types to be formed.• Scope of Issue: Allows ill-formed code to propagate beyond the type checker, causing crashes down the line. Such code was rejected prior to Swift 4.0.
• Origination: The removal of
AnyObjectas a magical protocol left this hole.• Risk: Low risk; we're checking a constraint consistently now. Any source code that breaks due to this was ill-formed and would likely have crashed later on anyway.
• Reviewed By: @rudkx
• Testing: Compiler regression tests, including new tests.
• Radar / SR: SR-6841 / rdar://problem/36884025