Why do we have uncommented and undocumented symbols in std.traits?

[Andrei Alexandrescu]

BooleanTypeOf
IntegralTypeOf
FloatingPointTypeOf
NumericTypeOf
UnsignedTypeOf
SignedTypeOf
CharTypeOf
StaticArrayTypeOf
DynamicArrayTypeOf
ArrayTypeOf
AssocArrayTypeOf
BuiltinTypeOf

Looking at their subtly repetitive definitions, they are specious to 
start with, but they have absolutely no comments so who knows what 
they're useful for.

People ask "what would do phobos better?" and it's ironic because 
literally whatever file I open there are dozens of immediate and urgent 
improvements to be done that scream at you.