[kjksf]

Because nil is a special thing in Go.

nil is not a value, it's a predeclared identifier.

it represents zero value for pointers, interfaces, maps, slices, channels and function types, representing an uninitialized value

len(nil) feels like it should work if you think of nil as the same as "value of empty array"

but what should be:

  var p *Struct
  len(p) 
  ???

There's no "length of zero-valued pointer".