types/geo: add support for ScalarMarshaler and ScalarUnmarshaler (#20158)

Add support for the still pending encoding.ScalarMarshaler and
encoding.ScalarUnmarshaler interfaces, approved in golang/go#56235.

This patch deprecates geo.Point.MarshalUint64 in favour of
geo.Point.MarshalScalar and also adds an inline directive for go fix.
The same applies for the UnmarshalUint64 and UnmarshalScalar methods.

Updates #16583

Signed-off-by: Simon Law <sfllaw@tailscale.com>

types/geo/point.go

@@ -166,7 +166,7 @@ func (p Point) AppendBinary(b []byte) ([]byte, error) {
 	return b, nil
 }
 
-// MarshalBinary implements [encoding.BinaryMarshaller]. The output matches that
+// MarshalBinary implements [encoding.BinaryMarshaler]. The output matches that
 // of calling [Point.AppendBinary].
 func (p Point) MarshalBinary() ([]byte, error) {
 	var b [8]byte
@@ -223,25 +223,43 @@ func (p Point) AppendText(b []byte) ([]byte, error) {
 	return b, nil
 }
 
-// MarshalText implements [encoding.TextMarshaller]. The output matches that
+// MarshalText implements [encoding.TextMarshaler]. The output matches that
 // of calling [Point.AppendText].
 func (p Point) MarshalText() ([]byte, error) {
 	var b [8]byte
 	return p.AppendText(b[:0])
 }
 
-// MarshalUint64 produces the same output as MashalBinary, encoded in a uint64.
-func (p Point) MarshalUint64() (uint64, error) {
+// MarshalScalar implements [encoding.ScalarMarshaler].
+// It produces the same output as MashalBinary, encoded in a uint64.
+func (p Point) MarshalScalar() (uint64, error) {
 	b, err := p.MarshalBinary()
 	return binary.NativeEndian.Uint64(b), err
 }
 
-// UnmarshalUint64 expects input formatted by MarshalUint64.
-func (p *Point) UnmarshalUint64(v uint64) error {
+// UnmarshalScalar implements [encoding.ScalarUnmarshaler].
+// It expects input formatted by MarshalScalar.
+func (p *Point) UnmarshalScalar(v uint64) error {
 	b := binary.NativeEndian.AppendUint64(nil, v)
 	return p.UnmarshalBinary(b)
 }
 
+// MarshalUint64 produces the same output as MashalBinary, encoded in a uint64.
+// Deprecated: this function simply calls [Point.MarshalScalar].
+//
+//go:fix inline
+func (p Point) MarshalUint64() (uint64, error) {
+	return p.MarshalScalar()
+}
+
+// UnmarshalUint64 expects input formatted by MarshalUint64.
+// Deprecated: this function simply calls [Point.UnmarshalScalar].
+//
+//go:fix inline
+func (p *Point) UnmarshalUint64(v uint64) error {
+	return p.UnmarshalScalar(v)
+}
+
 // IsZero reports if p is the zero value.
 func (p Point) IsZero() bool {
 	return p == Point{}