On Fri, Nov 8, 2019 at 6:46 AM Wilhelm Meier via Std-Discussion <std-discussion@lists.isocpp.org> wrote:
Hello all,

the member type size_type is an alias for size_t in std::array:

https://en.cppreference.com/w/cpp/container/array

The member type size_type in std::vector is an unspecified unsigned
integer type:

https://en.cppreference.com/w/cpp/container/vector

While I'm not sure we say it normatively, I believe that size_type for vector comes from its allocator, which std::array does not have.
 
Is this a documentation issue?

No.  It is normative.
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 Nevin ":-)" Liber  <mailto:nevin@cplusplusguy.com>  +1-847-691-1404