fix grpc: DP in unary calls

commit_hash:5d5e097f61771bcaa69a81c450cc32d64b37b6d5

Author: ivan-skryabin

grpc/include/userver/ugrpc/client/impl/unary_call.hpp

@@ -145,7 +145,7 @@ class UnaryCall final {
         }
 
         if (impl::IsTaskCancelledByDeadlinePropagation()) {
-            utils::unexpected{SpecialCaseCompletionType::kTimeoutDeadlinePropagated};
+            return utils::unexpected{SpecialCaseCompletionType::kTimeoutDeadlinePropagated};
         }
 
         return utils::unexpected{SpecialCaseCompletionType::kCancelled};
@@ -185,7 +185,7 @@ class UnaryCall final {
 
             case ugrpc::impl::AsyncMethodInvocation::WaitStatus::kCancelled:
                 if (impl::IsTaskCancelledByDeadlinePropagation()) {
-                    utils::unexpected{SpecialCaseCompletionType::kTimeoutDeadlinePropagated};
+                    return utils::unexpected{SpecialCaseCompletionType::kTimeoutDeadlinePropagated};
                 }
                 return utils::unexpected{SpecialCaseCompletionType::kCancelled};
 

universal/include/userver/utils/expected.hpp

@@ -30,7 +30,7 @@ class bad_expected_access : public std::exception {
 };
 
 template <class E>
-class unexpected {
+class [[nodiscard]] unexpected {
 public:
     unexpected(const E& error);
     unexpected(E&& error);