%destructor free_exp {psi_free_exp_free(&$$);}
%type impl_type {struct psi_impl_type*}
%destructor impl_type {psi_impl_type_free(&$$);}
%destructor free_exp {psi_free_exp_free(&$$);}
%type impl_type {struct psi_impl_type*}
%destructor impl_type {psi_impl_type_free(&$$);}