[clang-tidy][BUG][C++23][False Positive] on no name placeholder with std::string type

[yaoxinliu]

auto _ = std::vector<int>{};     // ok, no warning
auto _ = std::unique_ptr<int>{}; // ok, no warning
auto _ = "abc"sv;                // ok, no warning
auto _ = 1234;                   // ok, no warning
auto _ = 3.14;                   // ok, no warning
auto _ = "abcd"sv;               // ok, no warning
auto _ = {1, 2, 3};              // ok, no warning
auto _ = "abcd"s;                // warning by clang-tidy: Unused local variable '_' of type 'basic_string<char>'
auto _ = [] { return ""s; }();   // warning by clang-tidy: Unused local variable '_' of type 'basic_string<char>'

My clang-tidy version is 19.1.5.

Note that this false positive occur for std::string only, other types, even std::vector<int> and std::unique_ptr<int> which are obviously non-trivial classes, seem also good as expected.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: None (yaoxinliu)

``` auto _ = "abc"sv; auto _ = 1234; // ok auto _ = 3.14; // ok auto _ = "abcd"sv; // ok auto _ = {1, 2, 3}; // ok auto _ = "abcd"s; // warning by clang-tidy: Unused local variable '_' of type 'basic_string<char>' auto _ = [] { return ""s; }(); // warning by clang-tidy: Unused local variable '_' of type 'basic_string<char>' ```

My clang-tidy version is 19.1.5.

[yaoxinliu]

@HerrCai0907, why does this false positive occur for std::string only?

[HerrCai0907]

@HerrCai0907, why does this false positive occur for std::string only?

The other types are not non trivial. But i don't look details for the default non trivial type list.

[yaoxinliu]

@HerrCai0907, why does this false positive occur for std::string only?

The other types are not non trivial. But i don't look details for the default non trivial type list.

I tested std::vector<int> && std::unique_ptr<int>, which are obviously non-trivial types, and found them also ok as expected. @HerrCai0907

[HerrCai0907]

see https://clang.llvm.org/extra/clang-tidy/checks/bugprone/unused-local-non-trivial-variable.html#cmdoption-arg-IncludeTypes

[yaoxinliu]

see https://clang.llvm.org/extra/clang-tidy/checks/bugprone/unused-local-non-trivial-variable.html#cmdoption-arg-IncludeTypes

Thanks for your clarification.