There has been some confusion over the meaning of named vs. unnamed types. I for one was
confused about "float64" being a named type, and upon learning that, was
confused about what unnamed types are. It's obvious that anything to which a programmer
gives a name is a named type, but I don't think it's obvious that the predefined types
are named types.

The only place I see in the spec that talks about it is the following line:

"Named instances of the boolean, numeric, and string types are predeclared.
Composite types—array, struct, pointer, function, interface, slice, map, and channel
types—may be constructed using type literals."

With careful reading, this does say that float64 is a named type, but I think it could
be improved by saying something like "All of the predeclared boolean, numeric and
string types are named types." There is no confusion if a "named
instance" is the same as a "named type", and has a side bonus of someone
doing a find for "named type" would now easily find this line.

Secondly, this definition says nothing explicit about what an unnamed type is. It would
be nice if this was changed to explicitly state what are unnamed types.

While on the one hand I can see the argument "clearly []string is not a named type,
no one gave it a name", at the same time no Go programmer gave float64 a name
either. To me at least, the fact that

type Myfloat float64

is not assignable to a float64, while 

type Myfloatslice []float64

is assignable to a []float64 is surprising, and I would appreciate further clarification
in the spec.