[AST] Ignore UnvalidatedDeclsWithOpaqueReturnTypes in skipped functions

Author: rintaro

lib/AST/Module.cpp

@@ -3751,6 +3751,10 @@ void SourceFile::setAvailabilityScope(AvailabilityScope *scope) {
 
 ArrayRef<OpaqueTypeDecl *> SourceFile::getOpaqueReturnTypeDecls() {
   for (auto *vd : UnvalidatedDeclsWithOpaqueReturnTypes.takeVector()) {
+    if (vd->getDeclContext()->getInnermostSkippedFunctionContext()) {
+      // Ignore things in skipped functions.
+      continue;
+    }
     if (auto opaqueDecl = vd->getOpaqueResultTypeDecl()) {
       auto inserted = ValidatedOpaqueReturnTypes.insert(
                 {opaqueDecl->getOpaqueReturnTypeIdentifier().str(),