if for some reason (human error) you put a incorrect module name into a d
file then
the invalid module conflicts cause assertions.
D compiler 0.42 ALPHA
error message ---
Assertion failure: '0' on line 226 in file 'module.c'

to reproduce create two files
ftest.d -- [
module ftest;
import stest;

]
stest.d -- [
module ftest;

]
then try
dmd -c ftest.d

Mike.