Emitted when the compiler detects a case were it must implicitly convert a form of Unicode (a UnicodeString or a WideString) to an AnsiString (or AnsiChar). This is a potentially lossy conversion, since there may be characters in the string that cannot be represented in the code page to which the string will be converted. This warning is on by default. 

If you are certain that the data loss mentioned above will not happen, you can avoid this warning. To do this, cast the right operand to the left operand’s type manually. Generally, avoid assigning one string type to another.