copy_one_statement
valt = copy_one_statement(valt);
valf = copy_one_statement(valf);
stmt->case_statement = copy_one_statement(stmt->case_statement);
struct statement *switch_stmt = copy_one_statement(stmt->switch_statement);
stmt->iterator_pre_statement = copy_one_statement(stmt->iterator_pre_statement);
stmt->iterator_statement = copy_one_statement(stmt->iterator_statement);
stmt->iterator_post_statement = copy_one_statement(stmt->iterator_post_statement);
stmt->label_statement = copy_one_statement(stmt->label_statement);
add_statement(&dst->stmts, copy_one_statement(stmt));
dst->args = copy_one_statement(src->args);