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optimize implemention of Index template to improve build speed. #326

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Merged
mavenlin merged 1 commit into from
Mar 19, 2026
Merged

optimize implemention of Index template to improve build speed. #326

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15 changes: 7 additions & 8 deletions envpool/core/tuple_utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -27,14 +27,13 @@ template <class T, class Tuple>
struct Index;

template <class T, class... Types>
struct Index<T, std::tuple<T, Types...>> {
static constexpr std::size_t kValue = 0;
};

template <class T, class U, class... Types>
struct Index<T, std::tuple<U, Types...>> {
static constexpr std::size_t kValue =
1 + Index<T, std::tuple<Types...>>::kValue;
struct Index<T, std::tuple<Types...>> {
static_assert((std::is_same_v<T, Types> || ...), "Type not found in tuple");
static constexpr std::size_t kValue = [] {
std::size_t i = 0;
((std::is_same_v<T, Types> ? false : (++i, true)) && ...);

@chatgpt-codex-connector chatgpt-codex-connector Bot Mar 20, 2026

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P1 Badge Rewrite fold so Index does not trip clang-diagnostic-unused-value

.github/workflows/test.yml runs make clang-tidy, and .clang-tidy promotes every warning to an error (WarningsAsErrors: '*'). This fold expression now emits clang-diagnostic-unused-value for each Index<...> instantiation because the (++i, true) branch's value is discarded; I reproduced it with clang-tidy /tmp/index_test.cc -- -std=c++17 -I/workspace/envpool. Since Index is the helper behind Take() in envpool/core/dict.h, ordinary dict lookups will start failing the lint job.

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return i;
}();
};

template <class F, class K, class V, std::size_t... I>
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