diff --git a/src/base/bittorrent/torrenthandleimpl.cpp b/src/base/bittorrent/torrenthandleimpl.cpp
index 53f654d1d..431825a60 100644
--- a/src/base/bittorrent/torrenthandleimpl.cpp
+++ b/src/base/bittorrent/torrenthandleimpl.cpp
@@ -2133,9 +2133,9 @@ QVector<qreal> TorrentHandleImpl::availableFileFractions() const
         const TorrentInfo::PieceRange filePieces = info.filePieces(i);
 
         int availablePieces = 0;
-        for (int piece = filePieces.first(); piece <= filePieces.last(); ++piece) {
+        for (const int piece : filePieces)
             availablePieces += (piecesAvailability[piece] > 0) ? 1 : 0;
-        }
+
         res.push_back(static_cast<qreal>(availablePieces) / filePieces.size());
     }
     return res;
diff --git a/src/base/http/httperror.h b/src/base/http/httperror.h
index ab597ea64..853d6a7a9 100644
--- a/src/base/http/httperror.h
+++ b/src/base/http/httperror.h
@@ -39,8 +39,8 @@ public:
     QString statusText() const;
 
 private:
-    const int m_statusCode;
-    const QString m_statusText;
+    int m_statusCode;
+    QString m_statusText;
 };
 
 class BadRequestHTTPError : public HTTPError
diff --git a/src/base/indexrange.h b/src/base/indexrange.h
index a297d76ed..88719e5a0 100644
--- a/src/base/indexrange.h
+++ b/src/base/indexrange.h
@@ -38,7 +38,8 @@ class IndexInterval
 public:
     using IndexType = Index;
 
-    IndexInterval(IndexType first, IndexType last)  // add constexpr when using C++17
+    // TODO: add constexpr when using C++17
+    IndexInterval(const IndexType first, const IndexType last)
         : m_first {first}
         , m_last {last}
     {
@@ -56,12 +57,12 @@ public:
     }
 
 private:
-    const IndexType m_first;
-    const IndexType m_last;
+    IndexType m_first;
+    IndexType m_last;
 };
 
 template <typename T>
-constexpr IndexInterval<T> makeInterval(T first, T last)
+constexpr IndexInterval<T> makeInterval(const T first, const T last)
 {
     return {first, last};
 }
@@ -74,13 +75,55 @@ public:
     using IndexType = Index;
     using IndexDiffType = IndexDiff;
 
+    class Iterator
+    {
+    public:
+        explicit constexpr Iterator(const IndexType index)
+            : m_index {index}
+        {
+        }
+
+        constexpr Iterator(const Iterator &) = default;
+
+        constexpr IndexType operator*() const
+        {
+            return m_index;
+        }
+
+        constexpr Iterator &operator++()
+        {
+            ++m_index;
+            return *this;
+        }
+
+        constexpr Iterator operator++(int)
+        {
+            const Iterator iter {*this};
+            ++(*this);
+            return iter;
+        }
+
+        constexpr bool operator==(const Iterator &other) const
+        {
+            return (*(*this) == *other);
+        }
+
+        constexpr bool operator!=(const Iterator &other) const
+        {
+            return !(*this == other);
+        }
+
+    private:
+        IndexType m_index;
+    };
+
     constexpr IndexRange()
         : m_first {0}
         , m_size {0}
     {
     }
 
-    constexpr IndexRange(IndexType first, IndexDiffType size)
+    constexpr IndexRange(const IndexType first, const IndexDiffType size)
         : m_first {first}
         , m_size {size}
     {
@@ -92,14 +135,14 @@ public:
     {
     }
 
-    constexpr IndexType begin() const
+    constexpr Iterator begin() const
     {
-        return m_first;
+        return Iterator {m_first};
     }
 
-    constexpr IndexType end() const
+    constexpr Iterator end() const
     {
-        return (m_first + m_size);
+        return Iterator {m_first + m_size};
     }
 
     constexpr IndexDiffType size() const
diff --git a/src/gui/previewselectdialog.h b/src/gui/previewselectdialog.h
index 969a594e0..51d5a0213 100644
--- a/src/gui/previewselectdialog.h
+++ b/src/gui/previewselectdialog.h
@@ -48,6 +48,7 @@ class PreviewListDelegate;
 class PreviewSelectDialog final : public QDialog
 {
     Q_OBJECT
+    Q_DISABLE_COPY(PreviewSelectDialog)
 
 public:
     enum PreviewColumn
diff --git a/src/gui/rss/automatedrssdownloader.h b/src/gui/rss/automatedrssdownloader.h
index d158ecee2..0c2c3768a 100644
--- a/src/gui/rss/automatedrssdownloader.h
+++ b/src/gui/rss/automatedrssdownloader.h
@@ -53,6 +53,7 @@ namespace Ui
 class AutomatedRssDownloader : public QDialog
 {
     Q_OBJECT
+    Q_DISABLE_COPY(AutomatedRssDownloader)
 
 public:
     explicit AutomatedRssDownloader(QWidget *parent = nullptr);
diff --git a/src/webui/api/apierror.h b/src/webui/api/apierror.h
index e9181ca07..3879bd3af 100644
--- a/src/webui/api/apierror.h
+++ b/src/webui/api/apierror.h
@@ -47,5 +47,5 @@ public:
     APIErrorType type() const;
 
 private:
-    const APIErrorType m_type;
+    APIErrorType m_type;
 };