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[Runtime] Check for @objc existentials conforming to @objc protocols. #20217

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Merged
merged 1 commit into from
Nov 1, 2018
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[Runtime] Check for @objc existentials conforming to @objc protocols. #20217

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20 changes: 18 additions & 2 deletions stdlib/public/runtime/Casting.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -362,8 +362,24 @@ bool swift::_conformsToProtocol(const OpaqueValue *value,
#endif


case MetadataKind::Existential: // FIXME
case MetadataKind::ExistentialMetatype: // FIXME
case MetadataKind::Existential: {
#if SWIFT_OBJC_INTEROP
// If all protocols are @objc and at least one of them conforms to the
// protocol, succeed.
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Hm. What about non-@objc protocols that inherit from @objc protocols?

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Only @objc existentials can conform to protocols. A non-@objc protocol does not, even if it inherits from an @objc protocol. For example, the type checker rightly rejects this:

@objc protocol P { }
protocol Q: P { }
struct X<T:P> { }
typealias Y = X<Q>

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Oh, right, we aren't unboxing anything in this cast.

auto existential = cast<ExistentialTypeMetadata>(type);
if (!existential->isObjC())
return false;
for (auto existentialProto : existential->getProtocols()) {
if (protocol_conformsToProtocol(existentialProto.getObjCProtocol(),
protocol.getObjCProtocol()))
return true;
}
#endif

return false;
}

case MetadataKind::ExistentialMetatype:
default:
return false;
}
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7 changes: 7 additions & 0 deletions test/Runtime/demangleToMetadataObjC.swift
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Expand Up @@ -14,6 +14,7 @@ let DemangleToMetadataTests = TestSuite("DemangleToMetadataObjC")
@objc enum E: Int { case a }
@objc protocol P1 { }
protocol P2 { }
@objc protocol P3: P1 { }

DemangleToMetadataTests.test("@objc classes") {
expectEqual(type(of: C()), _typeByMangledName("4main1CC")!)
Expand Down Expand Up @@ -96,5 +97,11 @@ DemangleToMetadataTests.test("runtime conformance lookup via foreign superclasse
_typeByMangledName("ShySo18CFMutableStringRefaG")!)
}

class F<T: P1> { }

DemangleToMetadataTests.test("runtime conformance check for @objc protocol inheritance") {
expectEqual(F<P3>.self, _typeByMangledName("4main1FCyAA2P3PG")!)
}

runAllTests()