[Haskell-cafe] Decorating exceptions with backtrace information

Niklas Hambüchen mail at nh2.me
Fri May 8 17:27:35 UTC 2020

On 5/8/20 5:37 PM, Henning Thielemann wrote:
> I can imagine that it would be helpful for the user to get a stacked exception information like:
>    Parse error on line 42, column 23
>    while reading file "foo/bar"
>    while traversing directory "blabla"

That seems to be rather specific use case.
It'd be a cool feature but I'm not aware of any programming language following that interpretation so far.

I personally would be happy to be able to get the same type of stack trace for exceptions as in other programming langues (and as the proposal suggests).

> If you must debug exceptions, then this sounds like exceptions were abused for programming errors.

I'd be pretty happy to be able to debug them better; no matter if they were "abused" for anything or not, I must still debug them in practice.

Given that they traverse program flow invisibly (e.g. not lexically, like return values) and can become visible in different places than they arose, having a call stack to debug their creation would be useful.

> a callstack is not useful for a user.

Call stacks have been very useful to me as a user of non-Haskell tools so far, because they are excellent for attaching to bug reports and usually led to developers fixing my problems faster.

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