Re: [PATCH WIP] Use Levenshtein distance for various misspellings in C frontend v2

[Jeff Law <law at redhat dot com>]

On 09/16/2015 02:34 AM, Richard Biener wrote:
> Btw, this looks quite expensive - I'm sure we want to limit the effort
> here a bit.
A limiter is reasonable, though as it's been pointed out this only fires 
during error processing, so we probably have more leeway to take time 
and see if we can do better error recovery.

FWIW, I've used this algorithm in totally unrelated projects and while 
it seems expensive, it's worked out quite nicely.

> So while the idea might be an improvement to selected cases it can cause
> confusion as well.  And if using the suggestion for further parsing it can
> cause worse followup errors (unless we can limit such "fixup" use to the
> cases where we can parse the result without errors).  Consider
>
> foo()
> {
>    foz = 1;
> }
>
> if we suggest 'foo' instead of foz then we'll get a more confusing followup
> error if we actually use it.
True.  This kind of problem is probably inherent in this kind of "I'm 
going assume you meant..." error recovery mechanisms.

And just to be clear, even in a successful recovery scenario, we still 
issue an error.  The error recovery is just meant to try and give the 
user a hint what might have gone wrong and gracefully handle the case 
where they just made a minor goof.  Obviously the idea here is to cut 
down on the number of iterations of edit-compile cycle one has to do :-)


Jeff