Merge or-suggestions.hh into suggestions.hh

No real need for keeping a separate header for such a simple class.

This requires changing a bit `OrSuggestions<T>::operator*` to not throw
an `Error` to prevent a cyclic dependency. But since this error is only
thrown on programmer error, we can replace the whole method by a direct
call to `std::get` which will raise its own assertion if needs be.

src/libexpr/eval-cache.hh

@@ -3,7 +3,6 @@
 #include "sync.hh"
 #include "hash.hh"
 #include "eval.hh"
-#include "or-suggestions.hh"
 
 #include <functional>
 #include <variant>

src/libutil/or-suggestions.hh

@@ -1,64 +0,0 @@
-#include "suggestions.hh"
-#include "error.hh"
-
-namespace nix {
-
-// Either a value of type `T`, or some suggestions
-template<typename T>
-class OrSuggestions {
-public:
-    using Raw = std::variant<T, Suggestions>;
-
-    Raw raw;
-
-    T* operator ->()
-    {
-        return &**this;
-    }
-
-    T& operator *()
-    {
-        if (auto elt = std::get_if<T>(&raw))
-            return *elt;
-        throw Error("Invalid access to a failed value");
-    }
-
-    operator bool() const noexcept
-    {
-        return std::holds_alternative<T>(raw);
-    }
-
-    OrSuggestions(T t)
-        : raw(t)
-    {
-    }
-
-    OrSuggestions()
-        : raw(Suggestions{})
-    {
-    }
-
-    static OrSuggestions<T> failed(const Suggestions & s)
-    {
-        auto res = OrSuggestions<T>();
-        res.raw = s;
-        return res;
-    }
-
-    static OrSuggestions<T> failed()
-    {
-        return OrSuggestions<T>::failed(Suggestions{});
-    }
-
-    const Suggestions & getSuggestions()
-    {
-        static Suggestions noSuggestions;
-        if (const auto & suggestions = std::get_if<Suggestions>(&raw))
-            return *suggestions;
-        else
-            return noSuggestions;
-    }
-
-};
-
-}

src/libutil/suggestions.hh

@@ -42,4 +42,61 @@ public:
 
 std::ostream & operator<<(std::ostream & str, const Suggestion &);
 std::ostream & operator<<(std::ostream & str, const Suggestions &);
+
+// Either a value of type `T`, or some suggestions
+template<typename T>
+class OrSuggestions {
+public:
+    using Raw = std::variant<T, Suggestions>;
+
+    Raw raw;
+
+    T* operator ->()
+    {
+        return &**this;
+    }
+
+    T& operator *()
+    {
+        return std::get<T>(raw);
+    }
+
+    operator bool() const noexcept
+    {
+        return std::holds_alternative<T>(raw);
+    }
+
+    OrSuggestions(T t)
+        : raw(t)
+    {
+    }
+
+    OrSuggestions()
+        : raw(Suggestions{})
+    {
+    }
+
+    static OrSuggestions<T> failed(const Suggestions & s)
+    {
+        auto res = OrSuggestions<T>();
+        res.raw = s;
+        return res;
+    }
+
+    static OrSuggestions<T> failed()
+    {
+        return OrSuggestions<T>::failed(Suggestions{});
+    }
+
+    const Suggestions & getSuggestions()
+    {
+        static Suggestions noSuggestions;
+        if (const auto & suggestions = std::get_if<Suggestions>(&raw))
+            return *suggestions;
+        else
+            return noSuggestions;
+    }
+
+};
+
 }