Fix dtor handling issue introduced by fixing 3825

Commit:  d5aac8cc2bcc43e8753d889eff8e005f5c7443ce
Message: fix Issue 3825 - AAs entries are default initialized before the new value is evaluated
    https://github.com/D-Programming-Language/dmd/pull/1465/files#diff-31ec3d6838ade0264adec0944948507dR12919
    https://github.com/D-Programming-Language/dmd/pull/1465/files#diff-31ec3d6838ade0264adec0944948507dR12928
Fix dtor handling issue introduced by fixing 6508 and 5605

Commit:  dc49e1024ac2232967f235eea5e7bcfbf08734e2
Message: Issue 6508 - alias this doesn't work with AssignExp rhs
    https://github.com/D-Programming-Language/dmd/pull/322/files#diff-31ec3d6838ade0264adec0944948507dR9548

Commit:  4443f4295c1ee4b33794e6e2b3d050b1075a3599
Message: Separate side effects of tuple in DotVarExp::semantic()
    https://github.com/D-Programming-Language/dmd/pull/579/files#diff-31ec3d6838ade0264adec0944948507dR6686