Minor cleanup: IWYU, etc.

PiperOrigin-RevId: 608775453

src/google/protobuf/compiler/cpp/field.h

@@ -12,14 +12,17 @@
 #ifndef GOOGLE_PROTOBUF_COMPILER_CPP_FIELD_H__
 #define GOOGLE_PROTOBUF_COMPILER_CPP_FIELD_H__
 
+#include <cstddef>
 #include <cstdint>
 #include <memory>
 #include <string>
-#include <tuple>
 #include <vector>
 
 #include "absl/container/flat_hash_map.h"
 #include "absl/log/absl_check.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "absl/types/span.h"
 #include "google/protobuf/compiler/cpp/helpers.h"
 #include "google/protobuf/compiler/cpp/options.h"
 #include "google/protobuf/descriptor.h"
@@ -507,7 +510,8 @@ class FieldGeneratorTable {
 
   const FieldGenerator& get(const FieldDescriptor* field) const {
     ABSL_CHECK_EQ(field->containing_type(), descriptor_);
-    return fields_[field->index()];
+    ABSL_DCHECK_GE(field->index(), 0);
+    return fields_[static_cast<size_t>(field->index())];
   }
 
  private: