[llvm-bugs] [Bug 30260] New: optional<const T> not working

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=30260

            Bug ID: 30260
           Summary: optional<const T> not working
           Product: libc++
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: howard.hinnant at gmail.com
                CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com
    Classification: Unclassified

I expect this to compile and work:

    #include <experimental/optional>

    struct Foo {};

    std::experimental::optional<const Foo>
    someFunc();

    int
    main()
    {
        std::experimental::optional<const Foo> j;
        j.emplace(*someFunc());
    }

Instead I get compile-time errors such as:

In file included from test.cpp:22:
../libcxx/include/experimental/optional:274:17: error: no matching function for
call to 'operator new'
                ::new(_VSTD::addressof(__val_))
value_type(_VSTD::move(__x.__val_));
                ^~

I believe all that is needed (untested suggestion) is a const_cast of the
result of addressof on the way to new (several places).

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