[AST] Teach InheritedProtocolsRequest about synthesized protocol attributes

ClangImporter converts NS_SWIFT_SENDABLE into `SynthesizedProtocolAttr`
which needs to be recognized by the request that collects all of the
protocols that the given protocol inherits.

Author: xedin

lib/AST/NameLookup.cpp

@@ -3186,18 +3186,24 @@ SuperclassDeclRequest::evaluate(Evaluator &evaluator,
 ArrayRef<ProtocolDecl *>
 InheritedProtocolsRequest::evaluate(Evaluator &evaluator,
                                     ProtocolDecl *PD) const {
-  llvm::SmallVector<ProtocolDecl *, 2> result;
-  SmallPtrSet<const ProtocolDecl *, 2> known;
-  known.insert(PD);
+  llvm::SmallSetVector<ProtocolDecl *, 2> inherited;
+  auto addInherited = [&inherited, &PD](ProtocolDecl *P) {
+    if (PD != P)
+      inherited.insert(P);
+  };
+
+  for (auto attr : PD->getAttrs().getAttributes<SynthesizedProtocolAttr>()) {
+    addInherited(attr->getProtocol());
+  }
+
   bool anyObject = false;
   for (const auto &found : getDirectlyInheritedNominalTypeDecls(PD, anyObject)) {
     if (auto proto = dyn_cast<ProtocolDecl>(found.Item)) {
-      if (known.insert(proto).second)
-        result.push_back(proto);
+      addInherited(proto);
     }
   }
 
-  return PD->getASTContext().AllocateCopy(result);
+  return PD->getASTContext().AllocateCopy(inherited.getArrayRef());
 }
 
 ArrayRef<ValueDecl *>

test/Concurrency/sendable_objc_protocol_attr.swift

@@ -0,0 +1,40 @@
+// RUN: %empty-directory(%t/src)
+// RUN: %empty-directory(%t/sdk)
+// RUN: split-file %s %t/src
+
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck %t/src/main.swift \
+// RUN:   -import-objc-header %t/src/Test.h \
+// RUN:   -strict-concurrency=complete \
+// RUN:   -module-name main -I %t -verify
+
+// REQUIRES: objc_interop
+// REQUIRES: concurrency
+
+//--- Test.h
+#define NS_SWIFT_SENDABLE __attribute__((__swift_attr__("@Sendable")))
+
+#pragma clang assume_nonnull begin
+
+@import Foundation;
+
+NS_SWIFT_SENDABLE
+@protocol MyObjCProtocol <NSObject>
+@property (readonly, nonatomic) NSString *test;
+@end
+
+#pragma clang assume_nonnull end
+
+//--- main.swift
+struct MyStruct: Sendable {
+  let value: any MyObjCProtocol // Ok
+}
+
+extension Sendable {
+  func compute() {}
+}
+
+extension MyObjCProtocol {
+  func test() {
+    compute() // Ok
+  }
+}