Other: Safer user types

internal/safe/value_test.go

@@ -0,0 +1,37 @@
+package safe
+
+import "testing"
+
+func TestValue(t *testing.T) {
+	v := NewValue("foo")
+
+	v.Load(func(data string) {
+		if data != "foo" {
+			t.Error("expected foo")
+		}
+	})
+
+	v.Save("bar")
+
+	v.Load(func(data string) {
+		if data != "bar" {
+			t.Error("expected bar")
+		}
+	})
+
+	v.Mod(func(data *string) {
+		*data = "baz"
+	})
+
+	v.Load(func(data string) {
+		if data != "baz" {
+			t.Error("expected baz")
+		}
+	})
+
+	if LoadRet(v, func(data string) string {
+		return data
+	}) != "baz" {
+		t.Error("expected baz")
+	}
+}