[Bug c++/70229] error: constexpr constructor does not have empty body

[pangbw at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70229

--- Comment #1 from baoshan <pangbw at gmail dot com> ---
The error is triggered by the typedef clause, but it is valid according
standard C++11
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3376.pdf:

...
— either its function-body shall be = default, or the compound-statement of its
function-body shall
contain only
— null statements,
— static_assert-declarations
— typedef declarations and alias-declarations that do not define classes or
enumerations,
...