Not sure what you read or why bother commenting when you didn't but this sentence was in the article:
"But slices have mutable indexes. and many functions mutate the slices they're passed."
"But slices have mutable indexes. and many functions mutate the slices they're passed."
> It could allocate a new slice of interface values for you, and assign the concrete User values into corresponding indexes:
> [snipping example]
> Indeed, for getNames(users) this would actually work fine! But slices have mutable indexes. and many functions mutate the slices they're passed.
Again, this is not a real problem, and it could be pretty easily worked around. The real problem is that the slice type is neither covariant nor contravariant.