Change some explicit usage

src/core/database.h

@@ -129,7 +129,7 @@ class Database : public QObject {
 
 class MemoryDatabase : public Database {
  public:
-  MemoryDatabase(Application *app, QObject *parent = nullptr)
+  explicit MemoryDatabase(Application *app, QObject *parent = nullptr)
       : Database(app, parent, ":memory:") {}
   ~MemoryDatabase() override {
     // Make sure Qt doesn't reuse the same database

src/core/mimedata.h

@@ -31,7 +31,7 @@ class MimeData : public QMimeData {
   Q_OBJECT
 
  public:
-  MimeData(bool clear = false, bool play_now = false, bool enqueue = false, bool enqueue_next_now = false, bool open_in_new_playlist = false)
+  explicit MimeData(bool clear = false, bool play_now = false, bool enqueue = false, bool enqueue_next_now = false, bool open_in_new_playlist = false)
       : override_user_settings_(false),
         clear_first_(clear),
         play_now_(play_now),

src/core/qtsystemtrayicon.h

@@ -43,7 +43,7 @@ class QtSystemTrayIcon : public SystemTrayIcon {
   Q_OBJECT
 
  public:
-  QtSystemTrayIcon(QObject *parent = nullptr);
+  explicit QtSystemTrayIcon(QObject *parent = nullptr);
   ~QtSystemTrayIcon() override;
 
   void SetupMenu(QAction *previous, QAction *play, QAction *stop, QAction *stop_after, QAction *next, QAction *mute, QAction *love, QAction *quit) override;

src/core/scopedgobject.h

@@ -32,7 +32,7 @@ class ScopedGObject {
  public:
   ScopedGObject() : object_(nullptr) {}
 
-  explicit ScopedGObject(const ScopedGObject& other) : object_(nullptr) {
+  ScopedGObject(const ScopedGObject& other) : object_(nullptr) {
     reset(other.object_);
   }
 

src/core/urlhandler.h

@@ -57,7 +57,7 @@ class UrlHandler : public QObject {
       Error,
     };
 
-    LoadResult(const QUrl &original_url = QUrl(), const Type type = NoMoreTracks, const QUrl &stream_url = QUrl(), const Song::FileType filetype = Song::FileType_Stream, const int samplerate = -1, const int bit_depth = -1, const qint64 length_nanosec = -1, const QString error = QString());
+    explicit LoadResult(const QUrl &original_url = QUrl(), const Type type = NoMoreTracks, const QUrl &stream_url = QUrl(), const Song::FileType filetype = Song::FileType_Stream, const int samplerate = -1, const int bit_depth = -1, const qint64 length_nanosec = -1, const QString error = QString());
 
     // The url that the playlist item has in Url().
     // Might be something unplayable like lastfm://...

src/core/utilities.h

@@ -174,7 +174,7 @@ class ScopedWCharArray {
   QString ToString() const { return QString::fromWCharArray(data_.get()); }
 
   wchar_t *get() const { return data_.get(); }
-  operator wchar_t*() const { return get(); }
+  explicit operator wchar_t*() const { return get(); }
 
   int characters() const { return chars_; }
   int bytes() const { return (chars_ + 1)  *sizeof(wchar_t); }