fix

errors.go

@@ -1,9 +1,27 @@
 package copier
 
-import "errors"
+import (
+	"errors"
+	"fmt"
+	"reflect"
+)
 
 var (
 	ErrInvalidCopyDestination = errors.New("copy destination must be non-nil and addressable")
 	ErrInvalidCopyFrom        = errors.New("copy from must be non-nil and addressable")
-	ErrNotSupported           = errors.New("not supported")
+	ErrCircularReference      = errors.New("circular reference detected")
+	ErrMaxDepthExceeded       = errors.New("max depth exceeded")
 )
+
+type NotSupportedError struct {
+	SrcType reflect.Type
+	DstType reflect.Type
+}
+
+func (e *NotSupportedError) Error() string {
+	return fmt.Sprintf("unsupported type conversion from %s to %s", e.SrcType, e.DstType)
+}
+
+func ErrNotSupported(srcType, dstType reflect.Type) error {
+	return &NotSupportedError{SrcType: srcType, DstType: dstType}
+}