Circular dependencies in Phobos

[Jakob Ovrum via Digitalmars-d]

On Sunday, 3 January 2016 at 15:46:55 UTC, tsbockman wrote:
> How important is it to avoid circular dependencies in Phobos?
>
> I'm wondering because I have divided my work-in-progress 
> std.checkedint module into various submodules to make it easier 
> for people to import only the part they actually want to use.

Splitting modules into a circular package retains *some* of the 
benefits of split modules, like the smaller namespace in 
importing modules: while the whole tree is recursively pulled in, 
the user chooses which symbols to make available in the importing 
module. In D we have a number of conflict resolution mechanisms, 
including selective imports, so I don't count this as 
particularly useful.

The real benefits come when the split modules form a clean, 
non-circular dependency graph. Then we get the good stuff like 
faster compile times and smaller executables, can be understood 
in chunks etc.

I'm personally not a fan of circular modules, but I don't have 
strong opinions about them. In Phobos we have a number of modules 
with poor granularity that could be split into clean dependency 
trees. I don't know what to do, if anything, about circular 
modules that *can't* reasonably be split up as such.