This programme is intended to be used by any GHC developers working on the AST
and/or pretty printer by providing a way to check that the same AST is generated
from the pretty printed AST as from the original source.

i.e., it checks whether

    parse (ppr (parse s)) === parse s


This utility is also intended to be used in tests, so that when new features are
added the ability to round-trip the AST via ppr is tested.

Usage

In a test Makefile

  $(CHECK_PPR) "`'$(TEST_HC)' $(TEST_HC_OPTS) --print-libdir | tr -d '\r'`" FileToParse.hs

See examples in (REPO_HOME)/testsuite/tests/printer/Makefile

The utility generates the following files for ToBeTested.hs

  - ToBeTested.ppr.hs      : the ppr result
  - ToBeTested.hs.ast      : the AST of the original source
  - ToBeTested.hs.ast.new  : the AST of the re-parsed ppr source