This partial specialization of enable_if, for when the (template parameter) t_COND is false, guarantees that no typedef type is supplied. Note that this class definition is intentionally empty.
enable_if
t_COND
false
typedef
type
Declared in <bslmf_enableif.h>
<bslmf_enableif.h>
template<class t_TYPE> struct enable_if<false, t_TYPE>;