Hello,
(A) completion and documentation suggest straight creation:

       A      Create an array parameter with `${...=...}', `${...:=...}'
       or `${...::=...}'.  If this  flag  is
              repeated (as in `AA'), create an associative array
              parameter.  Assignment is made before sorting
              or padding; if field splitting is active, the word part is
              split before  assignment.   The  name
              part  may  be  a  subscripted  range  for ordinary arrays;
              the word part must be converted to an
              array, for example by using `${(AA)=name=...}' to activate
              field  splitting,  when  creating  an
              associative array.

This test:

% typeset -a overwrite_me=( 1 ); () { var_name="overwrite_me"; :
${(PA)var_name::=}; }; echo $overwrite_me"."${(t)overwrite_me}
.array

% () { local -a overwrite_me=( 1 ); () { var_name="overwrite_me"; :
${(PA)var_name::=}; }; echo $overwrite_me"."${(t)overwrite_me} }
.array-local

shows that parameter is reused if it exists, even if it exists on lower
scoping level. That's useful when coding, the patch adds one sentence
that clarifies this.

-- 
  Sebastian Gniazdowski
  psprint2@fastmail.com