IDE: use more efficient API to collect default implementations for protocol members. NFC (#19032)

Author: nkcsgexi

lib/IDE/IDETypeChecking.cpp

@@ -536,8 +536,6 @@ hasMergeGroup(MergeGroupKind Kind) {
 void swift::
 collectDefaultImplementationForProtocolMembers(ProtocolDecl *PD,
                     llvm::SmallDenseMap<ValueDecl*, ValueDecl*> &DefaultMap) {
-  Type BaseTy = PD->getDeclaredInterfaceType();
-  DeclContext *DC = PD->getInnermostDeclContext();
   auto HandleMembers = [&](DeclRange Members) {
     for (Decl *D : Members) {
       auto *VD = dyn_cast<ValueDecl>(D);
@@ -550,11 +548,8 @@ collectDefaultImplementationForProtocolMembers(ProtocolDecl *PD,
       if (VD->getBaseName().empty())
         continue;
 
-      ResolvedMemberResult Result = resolveValueMember(*DC, BaseTy,
-                                                       VD->getFullName());
-      assert(Result);
-      for (auto *Default : Result.getMemberDecls(InterestedMemberKind::All)) {
-        if (PD == Default->getDeclContext()->getExtendedProtocolDecl()) {
+      for (auto *Default: PD->lookupDirect(VD->getFullName())) {
+        if (Default->getDeclContext()->getExtendedProtocolDecl() == PD) {
           DefaultMap.insert({Default, VD});
         }
       }