Description

Compiling test-alt-string_cpp11 yields a warning with ICPC.

[8/137] Building CXX object tests/CMakeFiles/test-alt-string_cpp11.dir/src/unit-alt-string.cpp.o
/__w/json/json/tests/src/unit-alt-string.cpp(164): warning #1098: the qualifier on this friend declaration is ignored
      friend bool ::operator<(const char* /*op1*/, const alt_string& /*op2*/) noexcept;
                  ^

Reproduction steps

Run CI - see https://github.com/nlohmann/json/runs/7580471440?check_suite_focus=true

Expected vs. actual results

Expected: no warning.

Actual: warning

Minimal code example

No response

Error messages

[8/137] Building CXX object tests/CMakeFiles/test-alt-string_cpp11.dir/src/unit-alt-string.cpp.o
/__w/json/json/tests/src/unit-alt-string.cpp(164): warning #1098: the qualifier on this friend declaration is ignored
      friend bool ::operator<(const char* /*op1*/, const alt_string& /*op2*/) noexcept;
                  ^

Compiler and operating system

Intel 2021.5.0.20211109, Ubuntu 20.04.3 LTS

Library version

develop

Validation

• The bug also occurs if the latest version from the develop branch is used.
• I can successfully compile and run the unit tests.