Fix generics invariant violations in protocol requirement override checking #41622
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…h protocols We want to avoid feeding invalid type parameters into the Requirement Machine when checking if a protocol requirement overrides another protocol requirement in an inherited protocol. In order to do that we need to make sure the potential override has a compatible generic signature before we attempt substitution, just like we already do for classes. To do that, we need a way to 'rewrite' a generic signature for the base requirement into a generic signature that can be compared with the derived requirement, just as we do with class methods. For protocols this is a little easier than with class methods, since protocols only ever have a single 'Self' generic parameter. So just add the 'Self : DerivedProto' requirement to the base requirement's signature and rebuild.
…ocol requirements We need a substitution map written in terms of the base requirement's signature; getProtocolSubstitutions() alone was not enough because it does not include the extra generic parameters that the base requirement might have if it is itself generic.
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This avoids feeding invalid type parameters to the Requirement Machine when a protocol requirement looks similar to a protocol requirement in the inherited protocol but has an incompatible type. Fixes https://bugs.swift.org/browse/SR-15826 / rdar://problem/89641535.
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@swift-ci Please smoke test |
To avoid breaking the ABI of the standard library and possibly other modules, we can't actually enable the new accurate logic for checking protocol requirement overrides after all. Just skip the check if the protocol requirement is generic to get back the old behavior.
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@swift-ci Please smoke test |
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@swift-ci Please test source compatibility |
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@swift-ci Please smoke test Linux |
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We have to be careful not to feed an invalid type parameter into the Requirement Machine since that triggers asserts instead of returning bogus results like the GenericSignatureBuilder.
Fixes https://bugs.swift.org/browse/SR-15826 / rdar://problem/89641535.