implement safe version of operator?

return x1 < x2 ? x1 : x2 generates compile error because operator? required that both t1 and t2 need to be convertible to the same type. But only safe version of operator? would do this. Solution implement safe version of operator?

The issue names no files, tests, or entry points. Start by locating the library's existing operator? implementation and tests for mixed-type comparisons, then determine the intended safe conversion behavior and add coverage showing when the requested expression compiles and produces the expected result.

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