[chapel-lang/chapel] Add const checking for elements of tuple formals (

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Branch: refs/heads/master
Revision: a457fbc
Author: dlongnecke-cray
Log Message:

Add const checking for elements of tuple formals (#16041)

Add const checking for elements of tuple formals (#16041)

This PR adjusts the compiler to emit errors when a const element of
a tuple formal is modified. Prior to this PR the compiler would
compile programs such as the following without incident:


record r { var x: int = 0; }

proc modifyDefaultIntentFormal(tup) {
  tup[1] = new r(128);
}

proc test() {
  const a = (0, new r(0));
  modifyDefaultIntentFormal(a);
  writeln(a);
}
test();

The call to modifyDefaultIntentFormal incorrectly modifies the
second element of the tuple formal tup. Because tup has the
default argument intent, its second element should be passed by
const ref (because it is a record). Any modification of tup[1]
within the body of modifyDefaultIntentFormal should emit an error.