One line of the big compatibility expression was missing parentheses:

  (((p1.basetype = btPchar) or (p1.BaseType = btString)) and
    (p2.BaseType = btWideString) or (p2.BaseType = btUnicodeString)) or

'and' binds stronger than 'or', so the (p2 = btUnicodeString) term stood
alone: ANY destination type was considered assignment-compatible with a
UnicodeString source. Since script 'string' is btUnicodeString nowadays,
these all compiled without error and only failed at runtime (or
corrupted data):

  var i: Integer; s: string; ... i := s;
  var b: Boolean; s: string; ... b := s;
  var d: Double;  s: string; ... d := s;

With the added parentheses the term applies - as clearly intended - only
to btPchar/btString destinations. String-to-string, WideString and Char
conversions keep compiling as before.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>