chore: add type guard

Author: trim21

marshal.go

@@ -4,6 +4,10 @@ import (
 	"github.com/trim21/go-phpserialize/internal/encoder"
 )
 
+// make sure they are equal
+var _ Marshaler = encoder.Marshaler(nil)
+var _ encoder.Marshaler = Marshaler(nil)
+
 // Marshaler allow users to implement its own encoder.
 // **it's return value will not be validated**, please make sure you return valid encoded bytes.
 type Marshaler interface {

unmarshal.go

@@ -10,6 +10,10 @@ import (
 	"github.com/trim21/go-phpserialize/internal/errors"
 )
 
+// make sure they are equal
+var _ Unmarshaler = decoder.Unmarshaler(nil)
+var _ decoder.Unmarshaler = Unmarshaler(nil)
+
 type Unmarshaler interface {
 	UnmarshalPHP([]byte) error
 }