[m-dev.] preferences for error contexts

[Paul Bone]

On Fri, May 15, 2009 at 03:47:47PM +1000, Paul Bone wrote:
> On Fri, May 15, 2009 at 02:55:50PM +1000, Peter Wang wrote:
> > Hi,
> > 
> > We have some ugly error messages due to the way we use mmc -f, where
> > the filename and line number context ends up taking up most of the screen
> > width (don't ask).  Something like this:
> > 
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535: In clause for
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   predicate
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   `propagate3'/7:
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   in argument 3 of
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   call to predicate
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   `map.search'/3:
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   type error:
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   variable `I' has
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   type
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:
> > `(set.set((lalr.item)))',
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:   expected type was
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:
> > `(tree234.tree234((lalr.item),
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535:
> > (set.set((grammar.terminal)))))'.
> > 
> > 
> > I have a change that prints the context only on the first line.
> > The output ends up like:
> > 
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:535: In clause for
> >   predicate `propagate3'/7:
> >   in argument 3 of call to predicate `map.search'/3:
> >   type error:
> >   variable `I' has type `set.set(lalr.item)',
> >   expected type was `tree234.tree234(lalr.item, set.set(grammar.terminal))'.
> > /home/pwa/Work/gws_shorter_errors/extras/moose/lalr.m:538: In clause for
> >   predicate `propagate3'/7:
> >   in argument 1 of call to predicate `map.init'/1:
> >   type error:
> >   variable `X1' has type `set.set(lalr.item)',
> >   expected type was `tree234.tree234(V_V_1, V_V_2)'.
> > 
> > 
> > Currently this change would only kick in when the context is "too long".
> > However, one unexpected benefit is that in vim the :cn, :cp commands will
> > skip directly from one error to the next without going through the
> > intermediate lines, so maybe the new format should be used even for short
> > contexts?  On the other hand, the existing format is probably more readable
> > when the context is short.
> > 
> > I'd rather not add another option to choose.
> > 
> 
> I use the tool 'error' which takes the error output of mmc or some other
> compiler and adds the errors as source code comments to the relevant parts of
> my source files.  This will break with the new format, as in the example above
> only the text "In clause for" would be added to my source file.
> 

Off topic: I should actually bother to learn how to feed make output into an
editor so it can take me to the errors.  I'd prefer not to polute my source
file with errors even though they can be found and removed easily.

Eventually I'll set this up with Emacs once I (start and) finish my
mercury-mode for emacs.

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