Serialization: Fix serializing normal conformance xrefs for tuple conformances

Fixes rdar://problem/113707902.

Author: slavapestov

lib/Serialization/Serialization.cpp

@@ -1789,7 +1789,7 @@ Serializer::writeASTBlockEntity(ProtocolConformance *conformance) {
         Out, ScratchRecord,
         abbrCode,
         addDeclRef(normal->getProtocol()),
-        addDeclRef(normal->getType()->getAnyNominal()),
+        addDeclRef(normal->getDeclContext()->getSelfNominalTypeDecl()),
         addContainingModuleRef(normal->getDeclContext(),
                                /*ignoreExport=*/true));
     }

test/Serialization/Inputs/tuple_conformance_other.swift

@@ -0,0 +1,10 @@
+public struct G<T: Sendable> {
+}
+
+public func makeG<T: Sendable>(_: T.Type) -> G<T> {
+  return G<T>()
+}
+
+@_transparent public func makeVoidG() -> G<Void> {
+  return makeG(Void.self)
+}

test/Serialization/tuple_conformance.swift

@@ -0,0 +1,13 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module %S/Inputs/tuple_conformance_other.swift -emit-module-path %t/lib.swiftmodule -module-name lib
+// RUN: %target-swift-frontend -emit-sil %s -I %t | %FileCheck %s
+import lib
+
+public func doStuff() {
+  print(makeVoidG())
+}
+
+// CHECK-LABEL: sil public_external [transparent] @$s3lib9makeVoidGAA1GVyytGyF : $@convention(thin) () -> G<()> {
+// CHECK: [[FN:%.*]] = function_ref @$s3lib5makeGyAA1GVyxGxms8SendableRzlF : $@convention(thin) <τ_0_0 where τ_0_0 : Sendable> (@thick τ_0_0.Type) -> G<τ_0_0>
+// CHECK-NEXT: [[RESULT:%.*]] = apply [[FN]]<()>({{%.*}}) : $@convention(thin) <τ_0_0 where τ_0_0 : Sendable> (@thick τ_0_0.Type) -> G<τ_0_0>
+// CHECK-NEXT: return [[RESULT]] : $G<()>