General: Make operator bool() instances explicit

Prevents error-prone implicit conversions to bool.

include/amuse/AudioGroup.hpp

@@ -26,7 +26,7 @@ protected:
 
 public:
   SystemString getSampleBasePath(SampleId sfxId) const;
-  operator bool() const { return m_valid; }
+  explicit operator bool() const { return m_valid; }
   AudioGroup() = default;
   explicit AudioGroup(const AudioGroupData& data) { assign(data); }
   explicit AudioGroup(SystemStringView groupPath) { assign(groupPath); }

include/amuse/AudioGroupData.hpp

@@ -89,7 +89,9 @@ public:
   size_t getSdirSize() const { return m_sdirSz; }
   size_t getSampSize() const { return m_sampSz; }
 
-  operator bool() const { return m_proj != nullptr && m_pool != nullptr && m_sdir != nullptr && m_samp != nullptr; }
+  explicit operator bool() const {
+    return m_proj != nullptr && m_pool != nullptr && m_sdir != nullptr && m_samp != nullptr;
+  }
 
   DataFormat getDataFormat() const { return m_fmt; }
   bool getAbsoluteProjOffsets() const { return m_absOffs; }

include/amuse/Common.hpp

@@ -216,7 +216,7 @@ public:
   bool operator!=(const ObjTokenBase& other) const noexcept { return !operator==(other); }
   bool operator<(const ObjTokenBase& other) const noexcept { return m_obj < other.m_obj; }
   bool operator>(const ObjTokenBase& other) const noexcept { return m_obj > other.m_obj; }
-  operator bool() const noexcept { return m_obj != nullptr; }
+  explicit operator bool() const noexcept { return m_obj != nullptr; }
   void reset() noexcept {
     if (m_obj) {
       m_obj->decrement();

include/amuse/DirectoryEnumerator.hpp

@@ -48,7 +48,7 @@ public:
   DirectoryEnumerator(SystemStringView path, Mode mode = Mode::DirsThenFilesSorted, bool sizeSort = false,
                       bool reverse = false, bool noHidden = false);
 
-  operator bool() const { return m_entries.size() != 0; }
+  explicit operator bool() const { return m_entries.size() != 0; }
   size_t size() const { return m_entries.size(); }
   std::vector<Entry>::const_iterator begin() const { return m_entries.cbegin(); }
   std::vector<Entry>::const_iterator end() const { return m_entries.cend(); }

include/amuse/Sequencer.hpp

@@ -51,7 +51,7 @@ class Sequencer : public Entity {
     ~ChannelState();
     ChannelState() = default;
     ChannelState(Sequencer& parent, uint8_t chanId);
-    operator bool() const { return m_parent != nullptr; }
+    explicit operator bool() const { return m_parent != nullptr; }
 
     /** Voices corresponding to currently-pressed keys in channel */
     std::unordered_map<uint8_t, ObjToken<Voice>> m_chanVoxs;

include/amuse/SongState.hpp

@@ -94,7 +94,7 @@ class SongState {
 
     Track() = default;
     Track(SongState& parent, uint8_t midiChan, uint32_t loopStart, const TrackRegion* regions, uint32_t tempo);
-    operator bool() const { return m_parent != nullptr; }
+    explicit operator bool() const { return m_parent != nullptr; }
     void setRegion(const TrackRegion* region);
     void advanceRegion();
     bool advance(Sequencer& seq, double dt);

include/amuse/SoundMacroState.hpp

@@ -78,7 +78,7 @@ struct SoundMacroState {
     float evaluate(double time, const Voice& vox, const SoundMacroState& st) const;
 
     /** Determine if able to use */
-    operator bool() const { return m_comps.size() != 0; }
+    explicit operator bool() const { return m_comps.size() != 0; }
   };
 
   Evaluator m_volumeSel;