Module Fmlib_parse.Error_reporter

Convenience module to generate readable error messages.

An error reporter is a parser which reparses the input stream, extracts the failed code snippet and prints the error nicely formatted.

For semantic errors, the module needs support from the user to convert a semantic error into a pretty print document.

The error reporter generates a pretty print document (details about pretty print documents see Fmlib_pretty.Print) of the form

   code snippet containing the error with markers at the error

   description of the error

The description of the error is in case of a syntax error a description of what might have been expected at the error position and in case of a semantic error whatever the user provides as an error description.

The generated error report has one of the following forms:

• Syntax error:

    25 |      xxxx
    26 |
    27 |    line with error
                      ^
  
    I have encountered something unexpected. I was expecting one of
  
        - xxx
        - yyy
        - zzz
        ...

• Semantic error on one line:

    25 |      xxxx
    26 |
    27 |    line with error
                      ^^^^^
  
    User supplied description of the semantic error

• Semantic error spanning several lines

    25 |      xxxx
    26 |
                      v----------
    27 |    xxx yyy   error start
    28 |      err err err err err
    29 |          err err err
    30 |       err error end zzz
          -----------------^
  
    User supplied description of the semantic error