External Issue: set intersection

17401, "zhihuidu", "set intersection", "2021-03-15T02:17:18Z"

I declair three sets A,B,C as follows
var A= new set(int,parSafe = true);
var B= new set(int,parSafe = true);
var C= new set(int,parSafe = true);

When I do set intersection

C=A&B;

the compiler will give the following compiling errors.
$CHPL_HOME/modules/standard/Set.chpl:198: In method 'init=':
$CHPL_HOME/modules/standard/Set.chpl:200: error: Cannot replace an instantiated param field with another value
$CHPL_HOME/modules/standard/Set.chpl:200: note: field 'parSafe' has value 'false' but is set to 'true'
$CHPL_HOME/modules/standard/Set.chpl:669: called as (set(int(64),false)).init=(other: set(int(64),true)) from function '&'
set.chpl:97: called as &(a: set(int(64),true), b: set(int(64),true))
note: generic instantiations are underlined in the above callstack

However, if I declair A, B, and C as follows,

var A= new set(int);
var B= new set(int);
var C= new set(int);
the compliler can pass it .
If I declair A, B without parSafe = true, does it mean that parallel element adding will have problem? for example

Forall i in X with (ref A) {
A.add(i);
}