Caching in druntime TypeInfo classes

[Mike via Digitalmars-d]

On Tuesday, 30 June 2015 at 21:17:13 UTC, H. S. Teoh wrote:
> since TypeInfo's are supposed to be const, this operation is 
> illegal. Unless I cast away const, but that's a rather dirty 
> hack. The other problem is that the compiler hardcodes the 
> sizes of each TypeInfo instance, so it will refuse to compile 
> object.d anyway if the TypeInfo is expanded to have an extra 
> field for caching the result of hasCustomTohash(). But since we 
> have to modify the compiler now, my reaction was, why not have 
> the compiler compute this value itself? Since the compiler 
> already has all the information needed to compute this value. 
> We don't have to wait till runtime. The only drawback is adding 
> more complexity to the compiler, making it hard for other 
> efforts like SDC to implement D.
>

IMO the root cause of the trouble implementing your idea is the 
fact that the whole TypeInfo implementation is janky.  I think we 
should implement some flavor of Adam Ruppe's idea to move 
TypeInfo to the runtime 
(https://issues.dlang.org/show_bug.cgi?id=12270).  Then the 
implementation would be more straightforward...and it would solve 
another major problem that I'm having trying to use D for 
resource-constrained systems 
(http://bugzilla.gdcproject.org/show_bug.cgi?id=184) without 
having to resort to so much hackery.  It may also help reduce 
binary sizes on other platforms, which has come up a few times 
recently.

That's probably much more than you bargained for, but I have 
every intention on implementing it this year, and could use some 
help.

Mike