Mutually-recursive/cyclic module imports

[Isaac Dupree]

Duncan Coutts wrote:
> [...]
> 
> I'm not saying it's a problem with your proposal, I'd just like it to be
> taken into account. For example do dependency chasers need to grok just
> import lines and {-# SOURCE -#} pragmas or do they need to calculate
> fixpoints.

Good point.  What does the dependency chaser need to figure out?
- exactly what dependency order files must be compiled 
(e.g., ghc -c) ?
- what files (e.g., .hi) are needed to be findable by the 
e.g. (ghc -c) ?
- recompilation avoidance?

-Isaac