[libcxx-commits] [libcxx] [libc++] Mark string functions as [[nodiscard]] (PR #166524)

[Nikolas Klauser via libcxx-commits]

================
@@ -1344,24 +1354,26 @@ public:
     return size() == 0;
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 const_reference operator[](size_type __pos) const _NOEXCEPT {
+  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 const_reference
+  operator[](size_type __pos) const _NOEXCEPT {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__pos <= size(), "string index out of bounds");
     if (__builtin_constant_p(__pos) && !__fits_in_sso(__pos)) {
       return *(__get_long_pointer() + __pos);
     }
     return *(data() + __pos);
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference operator[](size_type __pos) _NOEXCEPT {
+  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference
+  operator[](size_type __pos) _NOEXCEPT {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__pos <= size(), "string index out of bounds");
     if (__builtin_constant_p(__pos) && !__fits_in_sso(__pos)) {
       return *(__get_long_pointer() + __pos);
     }
     return *(__get_pointer() + __pos);
   }
 
-  _LIBCPP_CONSTEXPR_SINCE_CXX20 const_reference at(size_type __n) const;
-  _LIBCPP_CONSTEXPR_SINCE_CXX20 reference at(size_type __n);
+  [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 const_reference at(size_type __n) const;
+  [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX20 reference at(size_type __n);
----------------
philnik777 wrote:

Why would you call this if you don't care about the returned thing? There are easier ways to throw than calling `at` with something you know to be out of range.

https://github.com/llvm/llvm-project/pull/166524