Rather than explain by deltas from something else, it might be easier just to write down precisely what you seek.
Let's say the hypothetical feature is selected via the GHC flag "--topo-sort". It would add a step before regular compilation and wouldn't affect any other flag: ghc -c --topo-sort fileA.hs fileB.hs ... This would first read in the specified source files and look at their module headers and import statements. It would build a graph of module dependencies _between_ the specified source files (ignoring circular dependencies), perform a topological sort on that graph, and proceed with compiling the source files in that order. As a consequence, if there is an order in which these modules can be successfully compiled, "--topo-sort" would choose such an order. In that sense, the above invocation would be equivalent to ghc -c fileB.hs fileA.hs ... (using some permutation of the original order specified) Another consequence is that any invocation of GHC in the form of ghc -c flags... sources.hs... with arbitrary flags would still work as usual when adding "--topo-sort". Quoting from the user manual:
In your program, you import a module Foo by saying import Foo. In --make mode or GHCi, GHC will look for a source file for Foo and arrange to compile it first. Without --make, GHC will look for the interface file for Foo, which should have been created by an earlier compilation of Foo.
The hypothetical "--topo-sort" flag would behave in the latter way, i.e. it would not require a source file for an unknown dependency. Hence, "--topo-sort" and "--make" would be conflicting options. I hope that clears up things a bit. Cheers Lars