message: Export SourceLocation and Position from lib/types.ts.
  I recently made these types non-buildable, so they aren't exported from
  ast-types anymore, but it would still be useful to have them available.
diff: import astTypes from "ast-types";
  export default astTypes;
  export * from "ast-types";
  +
  +// TODO Get these types from ast-types.
  +
  +export type Position = {
  + line: number;
  + column: number;
  +};
  +
  +export type SourceLocation = {
  + source?: string | null;
  + start: Position;
  + end: Position;
  +};
  