test/list.cpp list optional attributes not consistent with docs

These lines:

https://github.com/boostorg/spirit/blob/develop/test/x3/list.cpp#L81

    to:

https://github.com/boostorg/spirit/blob/develop/test/x3/list.cpp#L87

show the *same* grammar list expression:

    ('#' >> -alpha) % ','

can produce *different* attributes:

https://github.com/boostorg/spirit/blob/develop/test/x3/list.cpp#L81

which is a std::vector<optional<char>>

and:

https://github.com/boostorg/spirit/blob/develop/test/x3/list.cpp#L86

which is a std::vector<char>.

At least to me, that seems counter-intuitive.

Also, the attribute docs:

http://www.boost.org/doc/libs/1_65_0/libs/spirit/doc/html/spirit/qi/reference/operator/list.html

indicate the attribute should be:

    std::vector<optional<char> >

So why does the test in list.cpp with attribute std::vector<char> pass?

-regards,
Larry


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