Bug 17306 – dmd segfault on package imports

Test: a/root/fail.d: import root.core; b/root/core/base/package.d: (empty) b/root/core/package.d: import root.core.base; Compiler version: DMD64 D Compiler v2.075.0-devel-522263965 Compilation command: dmd a/root/fail.d -Ib Output: Segmentation fault Backtrace: #0 0x00000000005725fb in ScopeDsymbol::addAccessiblePackage(Package*, Prot) () #1 0x000000000054a888 in Import::semantic(Scope*) () #2 0x00000000005648b6 in Module::semantic(Scope*) () #3 0x000000000054a8db in Import::semantic(Scope*) () #4 0x00000000005648b6 in Module::semantic(Scope*) () #5 0x00000000005e37d0 in ddmd.mars.tryMain() () #6 0x00000000005e483f in D main () #7 0x0000000000732d80 in rt.dmain2._d_run_main() () #8 0x0000000000732ca8 in rt.dmain2._d_run_main() () #9 0x0000000000732d25 in rt.dmain2._d_run_main() () #10 0x0000000000732ca8 in rt.dmain2._d_run_main() () #11 0x0000000000732c14 in _d_run_main () #12 0x00000000005e4fe0 in main ()