partial bitcoin#25218: introduce generic 'Result' class and connect it to CreateTransaction and GetNewDestination

includes:
- 7a45c33

Author: kwvg

src/Makefile.am

@@ -367,6 +367,7 @@ BITCOIN_CORE_H = \
   util/overloaded.h \
   util/ranges.h \
   util/readwritefile.h \
+  util/result.h \
   util/underlying.h \
   util/serfloat.h \
   util/settings.h \

src/util/result.h

@@ -0,0 +1,43 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or https://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_RESULT_H
+#define BITCOIN_UTIL_RESULT_H
+
+#include <util/translation.h>
+#include <variant>
+
+/*
+ * 'BResult' is a generic class useful for wrapping a return object
+ * (in case of success) or propagating the error cause.
+*/
+template<class T>
+class BResult {
+private:
+    std::variant<bilingual_str, T> m_variant;
+
+public:
+    BResult() : m_variant(Untranslated("")) {}
+    BResult(const T& _obj) : m_variant(_obj) {}
+    BResult(const bilingual_str& error) : m_variant(error) {}
+
+    /* Whether the function succeeded or not */
+    bool HasRes() const { return std::holds_alternative<T>(m_variant); }
+
+    /* In case of success, the result object */
+    const T& GetObj() const {
+        assert(HasRes());
+        return std::get<T>(m_variant);
+    }
+
+    /* In case of failure, the error cause */
+    const bilingual_str& GetError() const {
+        assert(!HasRes());
+        return std::get<bilingual_str>(m_variant);
+    }
+
+    explicit operator bool() const { return HasRes(); }
+};
+
+#endif // BITCOIN_UTIL_RESULT_H