Use EValue::tryTo* (#19040)

Use tryTo in:

- parseTensorList (tensor_parser_exec_aten.cpp) — called .toTensor()
  on each element index of a TensorList.
- parseListOptionalType (tensor_parser.h) — called .toOptional<T>()
  on each element index of an OptionalTensorList.
- FreeCall instruction handler (method.cpp) — called .toTensor()
  on the value index being freed.

Unit tests cover parseTensorList and parseListOptionalType receiving
a non-matching EValue and expect Error::InvalidType.

Authored-with: Claude

---------

Co-authored-by: Github Executorch <github_executorch@arm.com>

Author: lucylq

runtime/executor/method.cpp

@@ -1538,17 +1538,16 @@ Error Method::execute_instruction() {
       // We know that instr_args_as_FreeCall is non-null because it was checked
       // at init time.
       auto free_call = instruction->instr_args_as_FreeCall();
-      auto& val = mutable_value(free_call->value_index());
-      if (val.isTensor()) {
-        auto& t = val.toTensor();
-        internal::reset_data_ptr(t);
-      } else {
+      auto t = mutable_value(free_call->value_index()).tryToTensor();
+      if (!t.ok()) {
         ET_LOG(
             Error,
             "FreeCall target at index %u is not a Tensor",
             static_cast<unsigned int>(free_call->value_index()));
-        err = Error::InvalidProgram;
+        err = t.error();
+        break;
       }
+      internal::reset_data_ptr(t.get());
     } break;
     default:
       ET_LOG(

runtime/executor/tensor_parser.h

@@ -97,8 +97,12 @@ ET_NODISCARD Result<BoxedEvalueList<std::optional<T>>> parseListOptionalType(
           InvalidProgram,
           "Invalid value index %" PRId32 " for ListOptional",
           index);
+      auto optional_result = values[index].tryToOptional<T>();
+      if (!optional_result.ok()) {
+        return optional_result.error();
+      }
       new (&optional_tensor_list[output_idx])
-          std::optional<T>(values[index].toOptional<T>());
+          std::optional<T>(std::move(optional_result.get()));
       evalp_list[output_idx] = &values[static_cast<size_t>(index)];
     }
     output_idx++;

runtime/executor/tensor_parser_exec_aten.cpp

@@ -98,10 +98,15 @@ ET_NODISCARD Result<BoxedEvalueList<executorch::aten::Tensor>> parseTensorList(
         "Invalid value index %" PRId32 " for TensorList",
         tensor_index);
 
+    auto tensor_result =
+        values[static_cast<size_t>(tensor_index)].tryToTensor();
+    if (!tensor_result.ok()) {
+      return tensor_result.error();
+    }
     // Placement new as the list elements are not initialized, so calling
     // copy assignment is not defined if it's non trivial.
-    new (&tensor_list[output_idx]) executorch::aten::Tensor(
-        values[static_cast<size_t>(tensor_index)].toTensor());
+    new (&tensor_list[output_idx])
+        executorch::aten::Tensor(std::move(tensor_result.get()));
     evalp_list[output_idx] = &values[static_cast<size_t>(tensor_index)];
     output_idx++;
   }

runtime/executor/test/tensor_parser_test.cpp

@@ -8,6 +8,8 @@
 
 #include <executorch/runtime/executor/tensor_parser.h>
 
+#include <cstring>
+
 #include <executorch/extension/data_loader/file_data_loader.h>
 #include <executorch/runtime/core/exec_aten/exec_aten.h>
 #include <executorch/runtime/core/tensor_layout.h>
@@ -19,14 +21,17 @@
 using namespace ::testing;
 using executorch::aten::ScalarType;
 using executorch::aten::Tensor;
+using executorch::runtime::BoxedEvalueList;
 using executorch::runtime::Error;
 using executorch::runtime::EValue;
 using executorch::runtime::FreeableBuffer;
 using executorch::runtime::Program;
 using executorch::runtime::Result;
 using executorch::runtime::Span;
 using executorch::runtime::TensorLayout;
+using executorch::runtime::deserialization::parseListOptionalType;
 using executorch::runtime::deserialization::parseTensor;
+using executorch::runtime::deserialization::parseTensorList;
 using executorch::runtime::deserialization::validateTensorLayout;
 using executorch::runtime::testing::ManagedMemoryManager;
 using torch::executor::util::FileDataLoader;
@@ -223,3 +228,60 @@ TEST(ValidateTensorLayoutTest, DimOrderSizeMismatchIsRejected) {
   EXPECT_EQ(
       validateTensorLayout(s_tensor, layout.get()), Error::InvalidExternalData);
 }
+
+// Helper to construct a flatbuffers::Vector<int32_t> from raw data.
+// FlatBuffer vectors are stored as [uint32_t length][T elements...].
+namespace {
+struct FlatVectorInt32 {
+  static const flatbuffers::Vector<int32_t>* create(
+      std::vector<uint8_t>& buf,
+      const std::vector<int32_t>& elements) {
+    buf.resize(sizeof(uint32_t) + elements.size() * sizeof(int32_t));
+    uint32_t len = static_cast<uint32_t>(elements.size());
+    memcpy(buf.data(), &len, sizeof(len));
+    if (!elements.empty()) {
+      memcpy(
+          buf.data() + sizeof(uint32_t),
+          elements.data(),
+          elements.size() * sizeof(int32_t));
+    }
+    return reinterpret_cast<const flatbuffers::Vector<int32_t>*>(buf.data());
+  }
+};
+} // namespace
+
+// parseTensorList should return an error when the EValue at the given index
+// is not a Tensor, instead of aborting.
+TEST_F(TensorParserTest, ParseTensorListRejectsNonTensorEValue) {
+  ManagedMemoryManager mmm(kDefaultNonConstMemBytes, kDefaultRuntimeMemBytes);
+
+  // Create an EValue array with a non-Tensor value at index 0.
+  EValue values[2];
+  values[0] = EValue(static_cast<int64_t>(42)); // Int, not Tensor
+  values[1] = EValue(static_cast<int64_t>(7));
+
+  // Create a vector with index 0 (pointing to the Int EValue).
+  std::vector<uint8_t> vec_buf;
+  auto* indices = FlatVectorInt32::create(vec_buf, {0});
+
+  auto result = parseTensorList(indices, values, 2, &mmm.get());
+  EXPECT_EQ(result.error(), Error::InvalidType);
+}
+
+// parseListOptionalType should return an error when the EValue at the given
+// index is neither None nor the expected type.
+TEST_F(TensorParserTest, ParseListOptionalTypeRejectsWrongType) {
+  ManagedMemoryManager mmm(kDefaultNonConstMemBytes, kDefaultRuntimeMemBytes);
+
+  // Create an EValue array with a non-Tensor, non-None value at index 0.
+  EValue values[2];
+  values[0] = EValue(static_cast<int64_t>(42)); // Int, not Tensor or None
+  values[1] = EValue(static_cast<int64_t>(7));
+
+  // Create a vector with index 0 (pointing to the Int EValue).
+  std::vector<uint8_t> vec_buf;
+  auto* indices = FlatVectorInt32::create(vec_buf, {0});
+
+  auto result = parseListOptionalType<Tensor>(indices, values, 2, &mmm.get());
+  EXPECT_EQ(result.error(), Error::InvalidType);
+}