Add and register full primitive constructor for XChaCha20-Poly1305

PiperOrigin-RevId: 699932175
Change-Id: I8bf50098682293e9149e0b1c2ad7a424e24253c5

aead/xchacha20poly1305/aead.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/tink-crypto/tink-go/v2/aead/subtle"
 	"github.com/tink-crypto/tink-go/v2/insecuresecretdataaccess"
+	"github.com/tink-crypto/tink-go/v2/key"
 	"github.com/tink-crypto/tink-go/v2/tink"
 )
 
@@ -68,3 +69,11 @@ func (ca *aead) Decrypt(ciphertext []byte, associatedData []byte) ([]byte, error
 	}
 	return plaintext, nil
 }
+
+func primitiveConstructor(key key.Key) (any, error) {
+	that, ok := key.(*Key)
+	if !ok {
+		return nil, fmt.Errorf("key is not a *xchacha20poly1305.Key")
+	}
+	return newAEAD(that)
+}

aead/xchacha20poly1305/xchacha20poly1305.go

@@ -22,6 +22,7 @@ import (
 	"github.com/tink-crypto/tink-go/v2/core/registry"
 	"github.com/tink-crypto/tink-go/v2/internal/internalregistry"
 	"github.com/tink-crypto/tink-go/v2/internal/protoserialization"
+	"github.com/tink-crypto/tink-go/v2/internal/registryconfig"
 )
 
 func init() {
@@ -40,4 +41,7 @@ func init() {
 	if err := protoserialization.RegisterParametersSerializer[*Parameters](&parametersSerializer{}); err != nil {
 		panic(fmt.Sprintf("xchacha20poly1305.init() failed: %v", err))
 	}
+	if err := registryconfig.RegisterPrimitiveConstructor[*Key](primitiveConstructor); err != nil {
+		panic(fmt.Sprintf("xchacha20poly1305.init() failed: %v", err))
+	}
 }