Immutable Variable Address

Alias variables are immutable with regards to their pointer address, thus re-assigning an address will return an error. For example the following code will not compile

FUNCTION main
    VAR
        foo AT bar : DINT;
        bar : DINT;
        baz : DINT;
    END_VAR

    foo := baz;     // Valid, because we are changing the pointers dereferenced value
    foo REF= baz;   // Invalid, `foo` is immutable with regards to it's pointer address
END_FUNCTION