Re: Improving 'syntax error, unexpected $end, expecting kEND'?

On Tue, 23 Oct 2007, Rick DeNatale wrote:

> On 10/22/07, Paul Brannan <[e-mail]> wrote:
> 
> > I don't think that specifying which element was missing the end
> > necessarily helps track down the problem.  Consider:
> >
   [class Foo;def foo;while true;end;return 42;end;1+2]
> >
> > With your proposed change I might expect to see something like:
> >
> >   Syntax error: unexpected end of file; expecting matching 'end' for 'class Foo'
> >
> > but blindly putting an 'end' after bar() might be wrong; the user might
> > have meant either:

Agreed. Doing anything without consideration will cause problems.  But
at least it tells the user where the interpreter began to get in knots.
        [examples trimmed]
> > but it's impossible to know without probing the user's brain (though
> > analyzing indentation could possibly help).
> 
> Way back in my college days ([...]) I took
> a programming course which used a slightly simplified academic version
> of PL/1 from Cornell called PL/C.
        [...]
> The PL/C compiler tried as hard as it could to correct syntax errors
> to get the "most" out of each run.
        [...]
> More often that not, IIRC this produced more amusing cascading errors
> than a real solution.

Agreed it is a less than perfect solution, but in terms of figuring
out what the interpreter is doing, it is more diagnostic info than
we get now.  We know that the open and closing statements are
balanced between the statement after that given and end of file.

        Hugh