Add missing const + Q_REQUIRED_RESULT

src/folder/hierarchicalfoldermatcher.cpp

@@ -18,7 +18,7 @@ HierarchicalFolderMatcher::HierarchicalFolderMatcher()
 {
 }
 
-bool HierarchicalFolderMatcher::isNull()
+bool HierarchicalFolderMatcher::isNull() const
 {
     return filterRegExps.empty();
 }

src/folder/hierarchicalfoldermatcher_p.h

@@ -23,13 +23,13 @@ class HierarchicalFolderMatcher
 public:
     HierarchicalFolderMatcher();
 
-    bool isNull();
+    Q_REQUIRED_RESULT bool isNull() const;
 
     void setFilter(const QString &filter, Qt::CaseSensitivity caseSensitivity);
 
-    bool matches(const QAbstractItemModel *model, const QModelIndex &start, int role = Qt::DisplayRole);
+    Q_REQUIRED_RESULT bool matches(const QAbstractItemModel *model, const QModelIndex &start, int role = Qt::DisplayRole);
 
-    QModelIndex findFirstMatch(const QAbstractItemModel *model, const QModelIndex &start, int role = Qt::DisplayRole);
+    Q_REQUIRED_RESULT QModelIndex findFirstMatch(const QAbstractItemModel *model, const QModelIndex &start, int role = Qt::DisplayRole);
 
 private:
     std::vector<QRegularExpression> filterRegExps;