message: Create AST type alias
diff: @@ -16,7 +16,8 @@ export {
  parseAndTraverseCode,
  transform,
  transformCopy,
  - Transformed
  + Transformed,
  + AST
  };
  export { mergeCommentsInto };
  @@ -34,11 +35,11 @@ function standardizeEOL(code: Code): Code {
  return code.replace(/\r/g, "");
  }
  -function parseAndTraverseCode(code: Code, opts: TraverseOptions): t.File {
  +function parseAndTraverseCode(code: Code, opts: TraverseOptions): AST {
  return traverseAST(parse(code), opts);
  }
  -function parse(code: Code): t.File {
  +function parse(code: Code): AST {
  return recast.parse(code, {
  parser: {
  parse: (source: Code) =>
  @@ -80,7 +81,7 @@ function parse(code: Code): t.File {
  });
  }
  -function traverseAST(ast: t.File, opts: TraverseOptions): t.File {
  +function traverseAST(ast: AST, opts: TraverseOptions): AST {
  traverse(ast, opts);
  return ast;
  }
  @@ -148,6 +149,8 @@ interface Transformed {
  hasCodeChanged: boolean;
  }
  +type AST = t.File;
  +
  function mergeCommentsInto<T extends t.Node>(
  node: T,
  commentedNodes: t.Node[]
  