Remove appbase as an external dependency.

lib/appbase/common/Outcome.hpp

@@ -0,0 +1,51 @@
+#pragma once
+
+namespace chatterino {
+
+struct SuccessTag {
+};
+
+struct FailureTag {
+};
+
+const SuccessTag Success{};
+const FailureTag Failure{};
+
+class Outcome
+{
+public:
+    Outcome(SuccessTag)
+        : success_(true)
+    {
+    }
+
+    Outcome(FailureTag)
+        : success_(false)
+    {
+    }
+
+    explicit operator bool() const
+    {
+        return this->success_;
+    }
+
+    bool operator!() const
+    {
+        return !this->success_;
+    }
+
+    bool operator==(const Outcome &other) const
+    {
+        return this->success_ == other.success_;
+    }
+
+    bool operator!=(const Outcome &other) const
+    {
+        return !this->operator==(other);
+    }
+
+private:
+    bool success_;
+};
+
+}  // namespace chatterino