I created a patch which gives a better error message when a cyclic dependency occurs between two modules due to both having module constructors and importing each other. When two modules "A" and "B" importing each other and having module constructors the error message with the patch will look like this: "Cyclic dependency in module B for import A" instead of "Cyclic dependency in module A".
Created attachment 784 [details] Patch for giving better cyclic dependency error messages
This bug is obsolete in light of the fixes I just checked in. See bug 4384. The runtime will now print the full cycle when a cyclic dependency is detected.