util/mak: delete long-deprecated, unused, pre-generics NonNil func

Updates tailscale#5590 (which deprecated it, 2.5 years ago)

Change-Id: I137e82855ee33d91e5639b909f7ca64e237ed6ba
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

Author: bradfitz

util/mak/mak.go

@@ -5,11 +5,6 @@
 // things, notably to maps, but also slices.
 package mak
 
-import (
-	"fmt"
-	"reflect"
-)
-
 // Set populates an entry in a map, making the map if necessary.
 //
 // That is, it assigns (*m)[k] = v, making *m if it was nil.
@@ -20,35 +15,6 @@ func Set[K comparable, V any, T ~map[K]V](m *T, k K, v V) {
 	(*m)[k] = v
 }
 
-// NonNil takes a pointer to a Go data structure
-// (currently only a slice or a map) and makes sure it's non-nil for
-// JSON serialization. (In particular, JavaScript clients usually want
-// the field to be defined after they decode the JSON.)
-//
-// Deprecated: use NonNilSliceForJSON or NonNilMapForJSON instead.
-func NonNil(ptr any) {
-	if ptr == nil {
-		panic("nil interface")
-	}
-	rv := reflect.ValueOf(ptr)
-	if rv.Kind() != reflect.Ptr {
-		panic(fmt.Sprintf("kind %v, not Ptr", rv.Kind()))
-	}
-	if rv.Pointer() == 0 {
-		panic("nil pointer")
-	}
-	rv = rv.Elem()
-	if rv.Pointer() != 0 {
-		return
-	}
-	switch rv.Type().Kind() {
-	case reflect.Slice:
-		rv.Set(reflect.MakeSlice(rv.Type(), 0, 0))
-	case reflect.Map:
-		rv.Set(reflect.MakeMap(rv.Type()))
-	}
-}
-
 // NonNilSliceForJSON makes sure that *slicePtr is non-nil so it will
 // won't be omitted from JSON serialization and possibly confuse JavaScript
 // clients expecting it to be present.

util/mak/mak_test.go

@@ -40,35 +40,6 @@ func TestSet(t *testing.T) {
 	})
 }
 
-func TestNonNil(t *testing.T) {
-	var s []string
-	NonNil(&s)
-	if len(s) != 0 {
-		t.Errorf("slice len = %d; want 0", len(s))
-	}
-	if s == nil {
-		t.Error("slice still nil")
-	}
-
-	s = append(s, "foo")
-	NonNil(&s)
-	if len(s) != 1 {
-		t.Errorf("len = %d; want 1", len(s))
-	}
-	if s[0] != "foo" {
-		t.Errorf("value = %q; want foo", s)
-	}
-
-	var m map[string]string
-	NonNil(&m)
-	if len(m) != 0 {
-		t.Errorf("map len = %d; want 0", len(s))
-	}
-	if m == nil {
-		t.Error("map still nil")
-	}
-}
-
 func TestNonNilMapForJSON(t *testing.T) {
 	type M map[string]int
 	var m M