@type op() ::
  {:rename_table, String.t()}
  | {:rename_column, String.t(), String.t()}
  | {:add_column, ExSQL.AST.ColumnDef.t()}
  | {:drop_column, String.t()}

@type t() :: %ExSQL.AST.AlterTable{
  name: String.t(),
  op: op(),
  schema: String.t() | nil
}