Consider the following snippet, with annotated type checking error.

type xer interface {
        x() string
}

func Print[T xer](s []T) {
        type Y T
        for _, v := range s {
                fmt.Println(v.x())
        }
        var y Y
        y.x() // <-- ERROR "y.x undefined (interface xer has no method x)"
}

This error is both inaccurate and (as a secondary concern) fails to mention the named type Y.

Update: per discussion below, let's disallow such declarations (as well as type Y = T) for now.

CC @griesemer