SILGen: Fix invalid SIL emitted when protocol requirement witnessed by base class convenience init #16899
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…y base class convenience init If the derived class is final and the base class is not, the protocol requirement can be witnessed by a non-required initializer. Non-required initializers have initializing but not allocating entry points in the vtable. The fix here statically dispatches to the allocating initializer instead. The test verifies that the allocating entry point uses alloc_ref_dynamic, so you will get an instance of the correct subclass. This fix does not handle the resilient case where the conformance is defined in a different module, and the original module adds an override of the convenience init later. I filed <rdar://problem/40639124> to track the resilient case. Fixes <rdar://problem/40003840>.
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jrose-apple
reviewed
May 30, 2018
| // Non-required initializers can witness a protocol requirement if the class | ||
| // is final, so we can statically dispatch to them. | ||
| if (!cast<ConstructorDecl>(decl)->isRequired()) | ||
| return WitnessDispatchKind::Static; |
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What happens if it is marked required (and non-overriding) but the class is also final?
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That should be caught above, where we check for final class or method.
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Oops, of course. Thanks.
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If the derived class is final and the base class is not, the
protocol requirement can be witnessed by a non-required
initializer. Non-required initializers have initializing
but not allocating entry points in the vtable.
The fix here statically dispatches to the allocating
initializer instead. The test verifies that the allocating
entry point uses alloc_ref_dynamic, so you will get an
instance of the correct subclass.
This fix does not handle the resilient case where the
conformance is defined in a different module, and the original
module adds an override of the convenience init later.
I filed rdar://problem/40639124 to track the resilient case.
Fixes rdar://problem/40003840.