This behavior can be controlled by the
[`httpmuxgo121` setting](/pkg/net/http/#ServeMux).

Go 1.22 added the [Alias type](/pkg/go/types#Alias) to [go/types](/pkg/go/types)
for the explicit representation of [type aliases](/ref/spec#Type_declarations).
Whether the type checker produces `Alias` types or not is controlled by the
[`gotypesalias` setting](/pkg/go/types#Alias).
For Go 1.22 it defaults to `gotypesalias=0`.