package fmlib_parse

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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
module type FAILED_PARSER = sig ... end

Needed functions from a failed parser i.e. a parser which has failed either with a syntax error or a semantic error.

module Make (Parser : FAILED_PARSER) : sig ... end

Generate the error reporter from a failed parser.