what am i even doing

merge/box.go

@@ -27,7 +27,7 @@ func strip[X any](f func(X) error) func(interface{}) error {
 	return func(v interface{}) error {
 		vv, ok := v.(X)
 		if !ok {
-			return fmt.Errorf("unable to merge value of type %T into value of type %T: %w", v, vv, typeMismatch)
+			return fmt.Errorf("unexpected %T value, expected %T instead: %w", v, vv, typeMismatch)
 		}
 		return f(vv)
 	}

ref/ref.go

@@ -0,0 +1,22 @@
+package ref
+
+import (
+	"fmt"
+)
+
+// New creates a reference for a given pointer
+func New[T any](v *T) Ref[T] {
+	if v == nil {
+		var zero T
+		return Ref[T]{ptr: &zero}
+	}
+	return Ref[T]{ptr: v}
+}
+
+// Ref is a read reference to some value T
+type Ref[T any] struct { ptr *T }
+
+// Val reads the value for this reference
+func (r Ref[T]) Val() T { return *r.ptr }
+
+func (r Ref[T]) String() string { return fmt.Sprintf("ref{%s}", *r.ptr) }