While the discussion about how to refactor test framework is not
finished (#1654), make this change: move `rm -rf build` in the
beginning of the test. For these reasons:
* it is useful to inspect the contents of the `build` directory
especially after the test failure
* if build crashes mid-test (e.g. process killed), next run should
not be affected by the `build` directory from the previous run
- Added initial implementations for terms and values
- Error messages converted to pretty printer
- Colorization for error messages
- Color and console width option both as command line and repl command
I don't know how complete this is, but it certainly detects some of the
most obvious cases which are most likely to be bugs.
While I'm at it, this is as good a time as any to add a general way of
reporting warnings, similar to the way of reporting errors.
