Why static analysis is the way to go

[H. S. Teoh]

On Fri, May 29, 2026 at 10:27:48AM +1200, Richard (Rikki) Andrew Cattermole via Digitalmars-d wrote:
> 
> On 29/05/2026 10:17 AM, H. S. Teoh wrote:
> >     We keep finding problems with them, nothrow in particular had a
> >     bug report within the last couple of months that we have yet to
> >     find a solution for.
> > 
> > 
> > Just curious, which bug is that?
> 
> https://github.com/dlang/dmd/issues/17906

But that bug has like 3-4 PRs referencing it.  Surely we're making
progress?

OTOH, inferrence has never been dmd's strong suit.  Throw(ha!) in
recursion, and I'm not surprised it got all fouled up.  This is
somewhat, albeit remotely, related to the whole inheritable attributes
thing.  Ideally, you want a wildcard value representing "the
nothrow-ness of this function" so that you can reason about recursive
calls in a sane way afterwards.  But there's no such thing in dmd, so
you have just a bunch of hacks to try to skirt around the issue somehow.

I wouldn't be surprised if similar issues exist with the other function
attributes when the function is recursive.  If .fun calls itself, is
.fun pure?  Well that depends on whether .fun pure to begin with.

Has anyone tried recursion that isn't immediately obvious, like .fun ->
.gun -> .fun, each level of which has nothrow-ness that depends on the
callee?  Betcha that doesn't work either.


T

-- 
There are two ways to write error-free programs; only the third one works.