struct S
{
   int t(A...)(A a) { return 0; }
   alias t this;
}

int main()
{
   S s;
   return s;
}

$ gdb --args dmd test.d

Program received signal SIGSEGV, Segmentation fault.
0x00000000004caee3 in TypeStruct::implicitConvTo(Type*) ()
(gdb) bt
#0  0x00000000004caee3 in TypeStruct::implicitConvTo(Type*) ()
#1  0x000000000040c527 in Expression::implicitConvTo(Type*) ()
#2  0x000000000040c2fd in Expression::implicitCastTo(Scope*, Type*) ()
#3  0x00000000004f3f0b in ReturnStatement::semantic(Scope*) ()
#4  0x00000000004ec6a2 in CompoundStatement::semantic(Scope*) ()
#5  0x000000000048defc in FuncDeclaration::semantic3(Scope*) ()
#6  0x00000000004ba294 in Module::semantic3() ()
#7  0x00000000004b83b2 in main ()