LSP: Fix MarkedString fromJson

fromJsonValue<T>(...) (with T = MarkedString) always tried to convert
the json value toObject() first. Which is wrong since it can be an
object or a string.

Fixes the broken hover text for the json language server.

Change-Id: Id69b4270238bea7068936a7d2142f4f94918f96b
Reviewed-by: David Schulz <david.schulz@qt.io>

src/libs/languageserverprotocol/languagefeatures.cpp

@@ -261,6 +261,12 @@ DocumentHighlightsResult::DocumentHighlightsResult(const QJsonValue &value)
     }
 }
 
+template<>
+MarkedString fromJsonValue<MarkedString>(const QJsonValue &value)
+{
+    return MarkedString(value);
+}
+
 MarkedString::MarkedString(const QJsonValue &value)
 {
     if (value.isObject())

src/libs/languageserverprotocol/languagefeatures.h

@@ -52,6 +52,9 @@ public:
     operator QJsonValue() const;
 };
 
+template<>
+LANGUAGESERVERPROTOCOL_EXPORT MarkedString fromJsonValue<MarkedString>(const QJsonValue &value);
+
 class LANGUAGESERVERPROTOCOL_EXPORT HoverContent
     : public std::variant<MarkedString, QList<MarkedString>, MarkupContent>
 {

src/libs/languageserverprotocol/lsputils.h

@@ -68,7 +68,7 @@ public:
         if (value.isArray()) {
             QList<T> values;
             values.reserve(value.toArray().count());
-            for (auto arrayValue : value.toArray())
+            for (const auto &arrayValue : value.toArray())
                 values << fromJsonValue<T>(arrayValue);
             *this = values;
         } else {