slog: remove reference to Attr "having a value"

Remove the HasValue method and references to an Attr having a value.

Attrs always have values, and one of those values is nil.

Change-Id: I410f85fb78c1722119e71b7c4e0b30278318083d
Reviewed-on: https://go-review.googlesource.com/c/exp/+/429839
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Jonathan Amsterdam <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: jba

slog/attr.go

@@ -150,7 +150,6 @@ func Any(key string, value any) Attr {
 func (a Attr) Key() string { return a.key }
 
 // Value returns the Attr's value as an any.
-// If the Attr does not have a value, it returns nil.
 func (a Attr) Value() any {
 	switch a.Kind() {
 	case AnyKind:
@@ -174,9 +173,6 @@ func (a Attr) Value() any {
 	}
 }
 
-// HasValue reports whether the Attr has a non-nil value.
-func (a Attr) HasValue() bool { return a.any != nil }
-
 // Int64 returns the Attr's value as an int64. It panics
 // if the value is not a signed integer.
 func (a Attr) Int64() int64 {

slog/attr_test.go

@@ -40,9 +40,6 @@ func TestNilAttr(t *testing.T) {
 	if g := n.Value(); g != nil {
 		t.Errorf("got %#v, want nil", g)
 	}
-	if n.HasValue() {
-		t.Error("n has value, wanted not")
-	}
 }
 
 func panics(f func()) (b bool) {