If there is only one element, this will not give the compiler problems.
--------------------
enum foo : type {
blah1,
blah2
}
--------------------
dmd -run test
test.d(1): identifier 'type' is not defined
test.d(1): type is used as a type
test.d(1): enum test.foo base type must be of integral type, not void
Assertion failure: '0' on line 160 in file 'enum.c'
abnormal program termination