build_constant
$$ = build_constant(gettyp($1->v_tspec), $1);
tnode_t *build_constant(type_t *, val_t *);
tnode_t *cn = build_constant(tn->tn_type, v);
return build_constant(tn->tn_type, v);
return build_constant(tn->tn_type, v);