[3.0] SILGen/IRGen: Lower protocol witness thunks for ObjC lightweight generics as pseudogeneric.

include/swift/SIL/SILType.h

@@ -561,6 +561,7 @@ NON_SIL_TYPE(LValue)
 CanSILFunctionType getNativeSILFunctionType(SILModule &M,
                         Lowering::AbstractionPattern orig,
                         CanAnyFunctionType substInterface,
+                        Optional<SILDeclRef> constant = None,
                         SILDeclRef::Kind kind = SILDeclRef::Kind::Func);
 
 inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, SILType T) {

lib/IRGen/GenProto.cpp

@@ -143,13 +143,18 @@ PolymorphicConvention::PolymorphicConvention(IRGenModule &IGM,
   : IGM(IGM), M(*IGM.getSwiftModule()), FnType(fnType) {
   initGenerics();
 
+  auto rep = fnType->getRepresentation();
+
   if (fnType->isPseudogeneric()) {
+    // Protocol witnesses still get Self metadata no matter what. The type
+    // parameters of Self are pseudogeneric, though.
+    if (rep == SILFunctionTypeRepresentation::WitnessMethod)
+      considerWitnessSelf(fnType);
+
     addPseudogenericFulfillments();
     return;
   }
 
-  auto rep = fnType->getRepresentation();
-
   if (rep == SILFunctionTypeRepresentation::WitnessMethod) {
     // Protocol witnesses always derive all polymorphic parameter
     // information from the Self argument. We also *cannot* consider other

lib/SIL/SILFunctionType.cpp

@@ -1021,6 +1021,7 @@ static CanSILFunctionType getNativeSILFunctionType(SILModule &M,
 CanSILFunctionType swift::getNativeSILFunctionType(SILModule &M,
                                        AbstractionPattern origType,
                                        CanAnyFunctionType substInterfaceType,
+                                       Optional<SILDeclRef> constant,
                                        SILDeclRef::Kind kind) {
   AnyFunctionType::ExtInfo extInfo;
 
@@ -1033,7 +1034,7 @@ CanSILFunctionType swift::getNativeSILFunctionType(SILModule &M,
     extInfo = substInterfaceType->getExtInfo();
   }
   return ::getNativeSILFunctionType(M, origType, substInterfaceType,
-                                    extInfo, None, kind);
+                                    extInfo, constant, kind);
 }
 
 //===----------------------------------------------------------------------===//
@@ -2070,6 +2071,7 @@ SILConstantInfo TypeConverter::getConstantOverrideInfo(SILDeclRef derived,
   // Build the SILFunctionType for the vtable thunk.
   CanSILFunctionType fnTy = getNativeSILFunctionType(M, basePattern,
                                                      overrideLoweredInterfaceTy,
+                                                     derived,
                                                      derived.kind);
 
   {

lib/SILGen/SILGenDecl.cpp

@@ -1737,7 +1737,8 @@ SILGenModule::emitProtocolWitness(ProtocolConformance *conformance,
   // Lower the witness type with the requirement's abstraction level.
   auto witnessSILFnType = getNativeSILFunctionType(M,
                                                    AbstractionPattern(reqtOrigTy),
-                                                   reqtSubstTy);
+                                                   reqtSubstTy,
+                                                   witness);
 
   // Mangle the name of the witness thunk.
   std::string nameBuffer;

test/IRGen/Inputs/objc_generic_protocol_conformance.h

@@ -0,0 +1,7 @@
+@import Foundation;
+
+@interface Foo <T> : NSObject
+
+- (void)foo;
+
+@end

test/IRGen/objc_generic_protocol_conformance.swift

@@ -0,0 +1,13 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-silgen %s -import-objc-header %S/Inputs/objc_generic_protocol_conformance.h | %FileCheck --check-prefix=SIL %s
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-ir %s -import-objc-header %S/Inputs/objc_generic_protocol_conformance.h | %FileCheck --check-prefix=IR %s
+
+// REQUIRES: objc_interop
+
+protocol P {
+  func foo()
+}
+
+extension Foo: P {}
+
+// SIL-LABEL: sil hidden [transparent] [thunk] @_TTWuRxs9AnyObjectrGCSo3Foo{{.*}} @pseudogeneric
+// IR-LABEL: define hidden void @_TTWuRxs9AnyObjectrGCSo3Foo{{.*}}(%CSo3Foo** noalias nocapture dereferenceable({{4|8}}), %swift.type*{{( %Self)?}}, i8**{{( %SelfWitnessTable)?}})