As Fix Anno Comments

Description

An asfix to asfix tool that reserves comments that were of the input source code by putting them in annotations of the AST.

It is difficult to decide what a comment actually comments on. The tool uses the heuristic that a comment is usually about the next construct. Therefore, it adds the comment to the first term with a constructor in the the subtree of the next symbol in the production rule. If this next symbol is a literal, then the comment will not be preserved.

Example

This simple tool works remarkably well. Let me illustrate this with an example input that I used during the development of this tool.

  /**
   * Voodoo
   */
  class Voodoo
  {
    /**
     * Bla bla
     */
    public void foo(/*let me explain this */ int x)
    {
      // just return
      return /* foo */ x;
    }
  }

An example fragment of the AST:

  Param([], Int, Id("x")){(Comment, "/*let me explain this */")}

The JavaFront pretty-printer has been extended to support these Comment annotations. The following pipe:

  sglr -2 -s CompilationUnit -p ~/wc/java-front/syn/v1.5/Java-15.tbl 
     -i ~/Foo.java
  | ./asfix-anno-comments
  | implode-asfix
  | pp-java

produces the following output:

  /**
   * Voodoo
   */
  class Voodoo
  {
    /**
     * Bla bla
     */
    public void foo(/*let me explain this */ int x)
    {
      // just return
      return /* foo */ x;
    }
  }