entity: [[nodiscard]] (close #501)

src/entt/entity/actor.hpp

@@ -129,7 +129,7 @@ struct basic_actor {
      * @return True if the actor has all the components, false otherwise.
      */
     template<typename... Component>
-    bool has() const {
+    [[nodiscard]] bool has() const {
         return reg->template has<Component...>(entt);
     }
 
@@ -139,13 +139,13 @@ struct basic_actor {
      * @return References to the components owned by the actor.
      */
     template<typename... Component>
-    decltype(auto) get() const {
+    [[nodiscard]] decltype(auto) get() const {
         return std::as_const(*reg).template get<Component...>(entt);
     }
 
     /*! @copydoc get */
     template<typename... Component>
-    decltype(auto) get() {
+    [[nodiscard]] decltype(auto) get() {
         return reg->template get<Component...>(entt);
     }
 
@@ -155,13 +155,13 @@ struct basic_actor {
      * @return Pointers to the components owned by the actor.
      */
     template<typename... Component>
-    auto try_get() const {
+    [[nodiscard]] auto try_get() const {
         return std::as_const(*reg).template try_get<Component...>(entt);
     }
 
     /*! @copydoc try_get */
     template<typename... Component>
-    auto try_get() {
+    [[nodiscard]] auto try_get() {
         return reg->template try_get<Component...>(entt);
     }
 
@@ -169,12 +169,12 @@ struct basic_actor {
      * @brief Returns a reference to the underlying registry.
      * @return A reference to the underlying registry.
      */
-    const registry_type & backend() const ENTT_NOEXCEPT {
+    [[nodiscard]] const registry_type & backend() const ENTT_NOEXCEPT {
         return *reg;
     }
 
     /*! @copydoc backend */
-    registry_type & backend() ENTT_NOEXCEPT {
+    [[nodiscard]] registry_type & backend() ENTT_NOEXCEPT {
         return const_cast<registry_type &>(std::as_const(*this).backend());
     }
 
@@ -182,7 +182,7 @@ struct basic_actor {
      * @brief Returns the entity associated with an actor.
      * @return The entity associated with the actor.
      */
-    entity_type entity() const ENTT_NOEXCEPT {
+    [[nodiscard]] entity_type entity() const ENTT_NOEXCEPT {
         return entt;
     }
 
@@ -190,7 +190,7 @@ struct basic_actor {
      * @brief Checks if an actor refers to a valid entity or not.
      * @return True if the actor refers to a valid entity, false otherwise.
      */
-    explicit operator bool() const {
+    [[nodiscard]] explicit operator bool() const {
         return reg && reg->valid(entt);
     }
 

src/entt/entity/entity.hpp

@@ -115,38 +115,38 @@ class null {
 
 public:
     template<typename Entity>
-    constexpr operator Entity() const ENTT_NOEXCEPT {
+    [[nodiscard]] constexpr operator Entity() const ENTT_NOEXCEPT {
         return Entity{traits_type<Entity>::entity_mask};
     }
 
-    constexpr bool operator==(null) const ENTT_NOEXCEPT {
+    [[nodiscard]] constexpr bool operator==(null) const ENTT_NOEXCEPT {
         return true;
     }
 
-    constexpr bool operator!=(null) const ENTT_NOEXCEPT {
+    [[nodiscard]] constexpr bool operator!=(null) const ENTT_NOEXCEPT {
         return false;
     }
 
     template<typename Entity>
-    constexpr bool operator==(const Entity entity) const ENTT_NOEXCEPT {
+    [[nodiscard]] constexpr bool operator==(const Entity entity) const ENTT_NOEXCEPT {
         return (to_integral(entity) & traits_type<Entity>::entity_mask) == to_integral(static_cast<Entity>(*this));
     }
 
     template<typename Entity>
-    constexpr bool operator!=(const Entity entity) const ENTT_NOEXCEPT {
+    [[nodiscard]] constexpr bool operator!=(const Entity entity) const ENTT_NOEXCEPT {
         return !(entity == *this);
     }
 };
 
 
 template<typename Entity>
-constexpr bool operator==(const Entity entity, null other) ENTT_NOEXCEPT {
+[[nodiscard]] constexpr bool operator==(const Entity entity, null other) ENTT_NOEXCEPT {
     return other.operator==(entity);
 }
 
 
 template<typename Entity>
-constexpr bool operator!=(const Entity entity, null other) ENTT_NOEXCEPT {
+[[nodiscard]] constexpr bool operator!=(const Entity entity, null other) ENTT_NOEXCEPT {
     return !(other == entity);
 }
 

src/entt/entity/group.hpp

@@ -110,7 +110,7 @@ public:
      * @return Number of existing components of the given type.
      */
     template<typename Component>
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return std::get<pool_type<Component> *>(pools)->size();
     }
 
@@ -118,7 +118,7 @@ public:
      * @brief Returns the number of entities that have the given components.
      * @return Number of entities that have the given components.
      */
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return handler->size();
     }
 
@@ -127,7 +127,7 @@ public:
      * allocated space for.
      * @return Capacity of the group.
      */
-    size_type capacity() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type capacity() const ENTT_NOEXCEPT {
         return handler->capacity();
     }
 
@@ -142,7 +142,7 @@ public:
      * @return True if the group or the pools are empty, false otherwise.
      */
     template<typename... Component>
-    bool empty() const ENTT_NOEXCEPT {
+    [[nodiscard]] bool empty() const ENTT_NOEXCEPT {
         if constexpr(sizeof...(Component) == 0) {
             return handler->empty();
         } else {
@@ -165,7 +165,7 @@ public:
      * @return A pointer to the array of components.
      */
     template<typename Component>
-    Component * raw() const ENTT_NOEXCEPT {
+    [[nodiscard]] Component * raw() const ENTT_NOEXCEPT {
         return std::get<pool_type<Component> *>(pools)->raw();
     }
 
@@ -184,7 +184,7 @@ public:
      * @return A pointer to the array of entities.
      */
     template<typename Component>
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return std::get<pool_type<Component> *>(pools)->data();
     }
 
@@ -200,7 +200,7 @@ public:
      *
      * @return A pointer to the array of entities.
      */
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return handler->data();
     }
 
@@ -218,7 +218,7 @@ public:
      *
      * @return An iterator to the first entity that has the given components.
      */
-    iterator begin() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
         return handler->begin();
     }
 
@@ -237,7 +237,7 @@ public:
      * @return An iterator to the entity following the last entity that has the
      * given components.
      */
-    iterator end() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator end() const ENTT_NOEXCEPT {
         return handler->end();
     }
 
@@ -246,7 +246,7 @@ public:
      * @return The first entity that has the given components if one exists, the
      * null entity otherwise.
      */
-    entity_type front() const {
+    [[nodiscard]] entity_type front() const {
         const auto it = begin();
         return it != end() ? *it : null;
     }
@@ -256,7 +256,7 @@ public:
      * @return The last entity that has the given components if one exists, the
      * null entity otherwise.
      */
-    entity_type back() const {
+    [[nodiscard]] entity_type back() const {
         const auto it = std::make_reverse_iterator(end());
         return it != std::make_reverse_iterator(begin()) ? *it : null;
     }
@@ -267,7 +267,7 @@ public:
      * @return An iterator to the given entity if it's found, past the end
      * iterator otherwise.
      */
-    iterator find(const entity_type entt) const {
+    [[nodiscard]] iterator find(const entity_type entt) const {
         const auto it = handler->find(entt);
         return it != end() && *it == entt ? it : end();
     }
@@ -277,7 +277,7 @@ public:
      * @param pos Position of the element to return.
      * @return The identifier that occupies the given position.
      */
-    entity_type operator[](const size_type pos) const {
+    [[nodiscard]] entity_type operator[](const size_type pos) const {
         return begin()[pos];
     }
 
@@ -286,7 +286,7 @@ public:
      * @param entt A valid entity identifier.
      * @return True if the group contains the given entity, false otherwise.
      */
-    bool contains(const entity_type entt) const {
+    [[nodiscard]] bool contains(const entity_type entt) const {
         return handler->contains(entt);
     }
 
@@ -308,7 +308,7 @@ public:
      * @return The components assigned to the entity.
      */
     template<typename... Component>
-    decltype(auto) get([[maybe_unused]] const entity_type entt) const {
+    [[nodiscard]] decltype(auto) get([[maybe_unused]] const entity_type entt) const {
         ENTT_ASSERT(contains(entt));
 
         if constexpr(sizeof...(Component) == 1) {
@@ -531,7 +531,7 @@ public:
      * @return Number of existing components of the given type.
      */
     template<typename Component>
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return std::get<pool_type<Component> *>(pools)->size();
     }
 
@@ -539,7 +539,7 @@ public:
      * @brief Returns the number of entities that have the given components.
      * @return Number of entities that have the given components.
      */
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return *length;
     }
 
@@ -549,7 +549,7 @@ public:
      * @return True if the group or the pools are empty, false otherwise.
      */
     template<typename... Component>
-    bool empty() const ENTT_NOEXCEPT {
+    [[nodiscard]] bool empty() const ENTT_NOEXCEPT {
         if constexpr(sizeof...(Component) == 0) {
             return !*length;
         } else {
@@ -575,7 +575,7 @@ public:
      * @return A pointer to the array of components.
      */
     template<typename Component>
-    Component * raw() const ENTT_NOEXCEPT {
+    [[nodiscard]] Component * raw() const ENTT_NOEXCEPT {
         return std::get<pool_type<Component> *>(pools)->raw();
     }
 
@@ -597,7 +597,7 @@ public:
      * @return A pointer to the array of entities.
      */
     template<typename Component>
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return std::get<pool_type<Component> *>(pools)->data();
     }
 
@@ -613,7 +613,7 @@ public:
      *
      * @return A pointer to the array of entities.
      */
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return std::get<0>(pools)->data();
     }
 
@@ -631,7 +631,7 @@ public:
      *
      * @return An iterator to the first entity that has the given components.
      */
-    iterator begin() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
         return std::get<0>(pools)->sparse_set<entity_type>::end() - *length;
     }
 
@@ -650,7 +650,7 @@ public:
      * @return An iterator to the entity following the last entity that has the
      * given components.
      */
-    iterator end() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator end() const ENTT_NOEXCEPT {
         return std::get<0>(pools)->sparse_set<entity_type>::end();
     }
 
@@ -659,7 +659,7 @@ public:
      * @return The first entity that has the given components if one exists, the
      * null entity otherwise.
      */
-    entity_type front() const {
+    [[nodiscard]] entity_type front() const {
         const auto it = begin();
         return it != end() ? *it : null;
     }
@@ -669,7 +669,7 @@ public:
      * @return The last entity that has the given components if one exists, the
      * null entity otherwise.
      */
-    entity_type back() const {
+    [[nodiscard]] entity_type back() const {
         const auto it = std::make_reverse_iterator(end());
         return it != std::make_reverse_iterator(begin()) ? *it : null;
     }
@@ -680,7 +680,7 @@ public:
      * @return An iterator to the given entity if it's found, past the end
      * iterator otherwise.
      */
-    iterator find(const entity_type entt) const {
+    [[nodiscard]] iterator find(const entity_type entt) const {
         const auto it = std::get<0>(pools)->find(entt);
         return it != end() && it >= begin() && *it == entt ? it : end();
     }
@@ -690,7 +690,7 @@ public:
      * @param pos Position of the element to return.
      * @return The identifier that occupies the given position.
      */
-    entity_type operator[](const size_type pos) const {
+    [[nodiscard]] entity_type operator[](const size_type pos) const {
         return begin()[pos];
     }
 
@@ -699,7 +699,7 @@ public:
      * @param entt A valid entity identifier.
      * @return True if the group contains the given entity, false otherwise.
      */
-    bool contains(const entity_type entt) const {
+    [[nodiscard]] bool contains(const entity_type entt) const {
         return std::get<0>(pools)->contains(entt) && (std::get<0>(pools)->index(entt) < (*length));
     }
 
@@ -721,7 +721,7 @@ public:
      * @return The components assigned to the entity.
      */
     template<typename... Component>
-    decltype(auto) get([[maybe_unused]] const entity_type entt) const {
+    [[nodiscard]] decltype(auto) get([[maybe_unused]] const entity_type entt) const {
         ENTT_ASSERT(contains(entt));
 
         if constexpr(sizeof...(Component) == 1) {
@@ -764,7 +764,7 @@ public:
      * @brief Checks whether the group can be sorted.
      * @return True if the group can be sorted, false otherwise.
      */
-    bool sortable() const ENTT_NOEXCEPT {
+    [[nodiscard]] bool sortable() const ENTT_NOEXCEPT {
         constexpr auto size = sizeof...(Owned) + sizeof...(Get) + sizeof...(Exclude);
         return *super == size;
     }

src/entt/entity/helper.hpp

@@ -36,7 +36,7 @@ struct as_view {
      * @return A newly created view.
      */
     template<typename Exclude, typename... Component>
-    operator entt::basic_view<Entity, Exclude, Component...>() const {
+    [[nodiscard]] operator entt::basic_view<Entity, Exclude, Component...>() const {
         return reg.template view<Component...>(Exclude{});
     }
 
@@ -86,7 +86,7 @@ struct as_group {
      * @return A newly created group.
      */
     template<typename Exclude, typename Get, typename... Owned>
-    operator entt::basic_group<Entity, Exclude, Get, Owned...>() const {
+    [[nodiscard]] operator entt::basic_group<Entity, Exclude, Get, Owned...>() const {
         return reg.template group<Owned...>(Get{}, Exclude{});
     }
 

src/entt/entity/observer.hpp

@@ -334,7 +334,7 @@ public:
      * @brief Returns the number of elements in an observer.
      * @return Number of elements.
      */
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return view.size();
     }
 
@@ -342,7 +342,7 @@ public:
      * @brief Checks whether an observer is empty.
      * @return True if the observer is empty, false otherwise.
      */
-    bool empty() const ENTT_NOEXCEPT {
+    [[nodiscard]] bool empty() const ENTT_NOEXCEPT {
         return view.empty();
     }
 
@@ -358,7 +358,7 @@ public:
      *
      * @return A pointer to the array of entities.
      */
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return view.data();
     }
 
@@ -370,7 +370,7 @@ public:
      *
      * @return An iterator to the first entity of the observer.
      */
-    iterator begin() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
         return view.sparse_set<entity_type>::begin();
     }
 
@@ -384,7 +384,7 @@ public:
      * @return An iterator to the entity following the last entity of the
      * observer.
      */
-    iterator end() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator end() const ENTT_NOEXCEPT {
         return view.sparse_set<entity_type>::end();
     }
 

src/entt/entity/registry.hpp

@@ -48,15 +48,15 @@ class basic_registry {
         static_assert(std::is_same_v<Component, std::decay_t<Component>>, "Invalid component type");
         std::size_t super{};
 
-        auto on_construct() ENTT_NOEXCEPT {
+        [[nodiscard]] auto on_construct() ENTT_NOEXCEPT {
             return sink{construction};
         }
 
-        auto on_update() ENTT_NOEXCEPT {
+        [[nodiscard]] auto on_update() ENTT_NOEXCEPT {
             return sink{update};
         }
 
-        auto on_destroy() ENTT_NOEXCEPT {
+        [[nodiscard]] auto on_destroy() ENTT_NOEXCEPT {
             return sink{destruction};
         }
 
@@ -180,7 +180,7 @@ class basic_registry {
     };
 
     template<typename Component>
-    const pool_handler<Component> & assure() const {
+    [[nodiscard]] const pool_handler<Component> & assure() const {
         const sparse_set<entity_type> *cpool;
 
         if constexpr(ENTT_FAST_PATH(has_type_index_v<Component>)) {
@@ -217,7 +217,7 @@ class basic_registry {
     }
 
     template<typename Component>
-    pool_handler<Component> & assure() {
+    [[nodiscard]] pool_handler<Component> & assure() {
         return const_cast<pool_handler<Component> &>(std::as_const(*this).template assure<Component>());
     }
 
@@ -244,7 +244,8 @@ public:
      */
     template<typename Component>
     void prepare() {
-        assure<Component>();
+        // suppress the warning due to the [[nodiscard]] attribute
+        static_cast<void>(assure<Component>());
     }
 
     /**
@@ -253,7 +254,7 @@ public:
      * @return Number of existing components of the given type.
      */
     template<typename Component>
-    size_type size() const {
+    [[nodiscard]] size_type size() const {
         return assure<Component>().size();
     }
 
@@ -261,7 +262,7 @@ public:
      * @brief Returns the number of entities created so far.
      * @return Number of entities created so far.
      */
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return entities.size();
     }
 
@@ -269,7 +270,7 @@ public:
      * @brief Returns the number of entities still in use.
      * @return Number of entities still in use.
      */
-    size_type alive() const {
+    [[nodiscard]] size_type alive() const {
         auto sz = entities.size();
         auto curr = destroyed;
 
@@ -308,7 +309,7 @@ public:
      * @return Capacity of the pool of the given component.
      */
     template<typename Component>
-    size_type capacity() const {
+    [[nodiscard]] size_type capacity() const {
         return assure<Component>().capacity();
     }
 
@@ -317,7 +318,7 @@ public:
      * allocated space for.
      * @return Capacity of the registry.
      */
-    size_type capacity() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type capacity() const ENTT_NOEXCEPT {
         return entities.capacity();
     }
 
@@ -343,7 +344,7 @@ public:
      * empty, false otherwise.
      */
     template<typename... Component>
-    bool empty() const {
+    [[nodiscard]] bool empty() const {
         if constexpr(sizeof...(Component) == 0) {
             return !alive();
         } else {
@@ -369,13 +370,13 @@ public:
      * @return A pointer to the array of components of the given type.
      */
     template<typename Component>
-    const Component * raw() const {
+    [[nodiscard]] const Component * raw() const {
         return assure<Component>().raw();
     }
 
     /*! @copydoc raw */
     template<typename Component>
-    Component * raw() {
+    [[nodiscard]] Component * raw() {
         return const_cast<Component *>(std::as_const(*this).template raw<Component>());
     }
 
@@ -393,7 +394,7 @@ public:
      * @return A pointer to the array of entities.
      */
     template<typename Component>
-    const entity_type * data() const {
+    [[nodiscard]] const entity_type * data() const {
         return assure<Component>().data();
     }
 
@@ -409,7 +410,7 @@ public:
      *
      * @return A pointer to the array of entities.
      */
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return entities.data();
     }
 
@@ -418,7 +419,7 @@ public:
      * @param entity An entity identifier, either valid or not.
      * @return True if the identifier is valid, false otherwise.
      */
-    bool valid(const entity_type entity) const {
+    [[nodiscard]] bool valid(const entity_type entity) const {
         const auto pos = size_type(to_integral(entity) & traits_type::entity_mask);
         return (pos < entities.size() && entities[pos] == entity);
     }
@@ -428,7 +429,7 @@ public:
      * @param entity An entity identifier, either valid or not.
      * @return The entity identifier without the version.
      */
-    static entity_type entity(const entity_type entity) ENTT_NOEXCEPT {
+    [[nodiscard]] static entity_type entity(const entity_type entity) ENTT_NOEXCEPT {
         return entity_type{to_integral(entity) & traits_type::entity_mask};
     }
 
@@ -437,7 +438,7 @@ public:
      * @param entity An entity identifier, either valid or not.
      * @return The version stored along with the given entity identifier.
      */
-    static version_type version(const entity_type entity) ENTT_NOEXCEPT {
+    [[nodiscard]] static version_type version(const entity_type entity) ENTT_NOEXCEPT {
         return version_type(to_integral(entity) >> traits_type::entity_shift);
     }
 
@@ -454,7 +455,7 @@ public:
      * @param entity A valid entity identifier.
      * @return Actual version for the given entity identifier.
      */
-    version_type current(const entity_type entity) const {
+    [[nodiscard]] version_type current(const entity_type entity) const {
         const auto pos = size_type(to_integral(entity) & traits_type::entity_mask);
         ENTT_ASSERT(pos < entities.size());
         return version_type(to_integral(entities[pos]) >> traits_type::entity_shift);
@@ -498,7 +499,7 @@ public:
      * @param hint A desired entity identifier.
      * @return A valid entity identifier.
      */
-    entity_type create(const entity_type hint) {
+    [[nodiscard]] entity_type create(const entity_type hint) {
         ENTT_ASSERT(hint != null);
         entity_type entt;
 
@@ -871,7 +872,7 @@ public:
      * @return True if the entity has all the components, false otherwise.
      */
     template<typename... Component>
-    bool has(const entity_type entity) const {
+    [[nodiscard]] bool has(const entity_type entity) const {
         ENTT_ASSERT(valid(entity));
         return (assure<Component>().contains(entity) && ...);
     }
@@ -890,7 +891,7 @@ public:
      * false otherwise.
      */
     template<typename... Component>
-    bool any(const entity_type entity) const {
+    [[nodiscard]] bool any(const entity_type entity) const {
         ENTT_ASSERT(valid(entity));
         return (assure<Component>().contains(entity) || ...);
     }
@@ -910,7 +911,7 @@ public:
      * @return References to the components owned by the entity.
      */
     template<typename... Component>
-    decltype(auto) get([[maybe_unused]] const entity_type entity) const {
+    [[nodiscard]] decltype(auto) get([[maybe_unused]] const entity_type entity) const {
         ENTT_ASSERT(valid(entity));
 
         if constexpr(sizeof...(Component) == 1) {
@@ -922,7 +923,7 @@ public:
 
     /*! @copydoc get */
     template<typename... Component>
-    decltype(auto) get([[maybe_unused]] const entity_type entity) {
+    [[nodiscard]] decltype(auto) get([[maybe_unused]] const entity_type entity) {
         ENTT_ASSERT(valid(entity));
 
         if constexpr(sizeof...(Component) == 1) {
@@ -957,7 +958,7 @@ public:
      * @return Reference to the component owned by the entity.
      */
     template<typename Component, typename... Args>
-    decltype(auto) get_or_emplace(const entity_type entity, Args &&... args) {
+    [[nodiscard]] decltype(auto) get_or_emplace(const entity_type entity, Args &&... args) {
         ENTT_ASSERT(valid(entity));
         auto &cpool = assure<Component>();
         return cpool.contains(entity) ? cpool.get(entity) : cpool.emplace(*this, entity, std::forward<Args>(args)...);
@@ -976,7 +977,7 @@ public:
      * @return Pointers to the components owned by the entity.
      */
     template<typename... Component>
-    auto try_get([[maybe_unused]] const entity_type entity) const {
+    [[nodiscard]] auto try_get([[maybe_unused]] const entity_type entity) const {
         ENTT_ASSERT(valid(entity));
 
         if constexpr(sizeof...(Component) == 1) {
@@ -988,7 +989,7 @@ public:
 
     /*! @copydoc try_get */
     template<typename... Component>
-    auto try_get([[maybe_unused]] const entity_type entity) {
+    [[nodiscard]] auto try_get([[maybe_unused]] const entity_type entity) {
         ENTT_ASSERT(valid(entity));
 
         if constexpr(sizeof...(Component) == 1) {
@@ -1051,7 +1052,7 @@ public:
      * @param entity A valid entity identifier.
      * @return True if the entity has no components assigned, false otherwise.
      */
-    bool orphan(const entity_type entity) const {
+    [[nodiscard]] bool orphan(const entity_type entity) const {
         ENTT_ASSERT(valid(entity));
         return std::none_of(pools.cbegin(), pools.cend(), [entity](auto &&pdata) { return pdata.pool && pdata.pool->contains(entity); });
     }
@@ -1104,7 +1105,7 @@ public:
      * @return A temporary sink object.
      */
     template<typename Component>
-    auto on_construct() {
+    [[nodiscard]] auto on_construct() {
         return assure<Component>().on_construct();
     }
 
@@ -1129,7 +1130,7 @@ public:
      * @return A temporary sink object.
      */
     template<typename Component>
-    auto on_update() {
+    [[nodiscard]] auto on_update() {
         return assure<Component>().on_update();
     }
 
@@ -1156,7 +1157,7 @@ public:
      * @return A temporary sink object.
      */
     template<typename Component>
-    auto on_destroy() {
+    [[nodiscard]] auto on_destroy() {
         return assure<Component>().on_destroy();
     }
 
@@ -1289,14 +1290,14 @@ public:
      * @return A newly created view.
      */
     template<typename... Component, typename... Exclude>
-    entt::basic_view<Entity, exclude_t<Exclude...>, Component...> view(exclude_t<Exclude...> = {}) const {
+    [[nodiscard]] entt::basic_view<Entity, exclude_t<Exclude...>, Component...> view(exclude_t<Exclude...> = {}) const {
         static_assert(sizeof...(Component) > 0, "Exclusion-only views are not supported");
         return { assure<std::decay_t<Component>>()..., assure<Exclude>()... };
     }
 
     /*! @copydoc view */
     template<typename... Component, typename... Exclude>
-    entt::basic_view<Entity, exclude_t<Exclude...>, Component...> view(exclude_t<Exclude...> = {}) {
+    [[nodiscard]] entt::basic_view<Entity, exclude_t<Exclude...>, Component...> view(exclude_t<Exclude...> = {}) {
         static_assert(sizeof...(Component) > 0, "Exclusion-only views are not supported");
         return { assure<std::decay_t<Component>>()..., assure<Exclude>()... };
     }
@@ -1308,7 +1309,7 @@ public:
      * otherwise.
      */
     template<typename... Component>
-    bool sortable() const {
+    [[nodiscard]] bool sortable() const {
         return !(assure<Component>().super || ...);
     }
 
@@ -1340,7 +1341,7 @@ public:
      * @return A newly created group.
      */
     template<typename... Owned, typename... Get, typename... Exclude>
-    entt::basic_group<Entity, exclude_t<Exclude...>, get_t<Get...>, Owned...> group(get_t<Get...>, exclude_t<Exclude...> = {}) {
+    [[nodiscard]] entt::basic_group<Entity, exclude_t<Exclude...>, get_t<Get...>, Owned...> group(get_t<Get...>, exclude_t<Exclude...> = {}) {
         static_assert(sizeof...(Owned) + sizeof...(Get) > 0, "Exclusion-only views are not supported");
         static_assert(sizeof...(Owned) + sizeof...(Get) + sizeof...(Exclude) > 1, "Single component groups are not allowed");
 
@@ -1436,7 +1437,7 @@ public:
      * @return A newly created group.
      */
     template<typename... Owned, typename... Get, typename... Exclude>
-    entt::basic_group<Entity, exclude_t<Exclude...>, get_t<Get...>, Owned...> group(get_t<Get...>, exclude_t<Exclude...> = {}) const {
+    [[nodiscard]] entt::basic_group<Entity, exclude_t<Exclude...>, get_t<Get...>, Owned...> group(get_t<Get...>, exclude_t<Exclude...> = {}) const {
         static_assert(std::conjunction_v<std::is_const<Owned>..., std::is_const<Get>...>, "Invalid non-const type");
         return const_cast<basic_registry *>(this)->group<Owned...>(entt::get<Get...>, exclude<Exclude...>);
     }
@@ -1451,7 +1452,7 @@ public:
      * @return A newly created group.
      */
     template<typename... Owned, typename... Exclude>
-    entt::basic_group<Entity, exclude_t<Exclude...>, get_t<>, Owned...> group(exclude_t<Exclude...> = {}) {
+    [[nodiscard]] entt::basic_group<Entity, exclude_t<Exclude...>, get_t<>, Owned...> group(exclude_t<Exclude...> = {}) {
         return group<Owned...>(entt::get<>, exclude<Exclude...>);
     }
 
@@ -1465,7 +1466,7 @@ public:
      * @return A newly created group.
      */
     template<typename... Owned, typename... Exclude>
-    entt::basic_group<Entity, exclude_t<Exclude...>, get_t<>, Owned...> group(exclude_t<Exclude...> = {}) const {
+    [[nodiscard]] entt::basic_group<Entity, exclude_t<Exclude...>, get_t<>, Owned...> group(exclude_t<Exclude...> = {}) const {
         static_assert(std::conjunction_v<std::is_const<Owned>...>, "Invalid non-const type");
         return const_cast<basic_registry *>(this)->group<Owned...>(exclude<Exclude...>);
     }
@@ -1491,7 +1492,7 @@ public:
      * @return A newly created runtime view.
      */
     template<typename It>
-    entt::basic_runtime_view<Entity> runtime_view(It first, It last) const {
+    [[nodiscard]] entt::basic_runtime_view<Entity> runtime_view(It first, It last) const {
         std::vector<const sparse_set<Entity> *> selected(std::distance(first, last));
 
         std::transform(first, last, selected.begin(), [this](const auto ctype) {
@@ -1602,7 +1603,7 @@ public:
      * @return A reference to the object in the context of the registry.
      */
     template<typename Type, typename... Args>
-    Type & ctx_or_set(Args &&... args) {
+    [[nodiscard]] Type & ctx_or_set(Args &&... args) {
         auto *value = try_ctx<Type>();
         return value ? *value : set<Type>(std::forward<Args>(args)...);
     }
@@ -1614,14 +1615,14 @@ public:
      * registry, a null pointer otherwise.
      */
     template<typename Type>
-    const Type * try_ctx() const {
+    [[nodiscard]] const Type * try_ctx() const {
         auto it = std::find_if(vars.cbegin(), vars.cend(), [](auto &&var) { return var.type_id == type_info<Type>::id(); });
         return it == vars.cend() ? nullptr : static_cast<const Type *>(it->value.get());
     }
 
     /*! @copydoc try_ctx */
     template<typename Type>
-    Type * try_ctx() {
+    [[nodiscard]] Type * try_ctx() {
         return const_cast<Type *>(std::as_const(*this).template try_ctx<Type>());
     }
 
@@ -1638,7 +1639,7 @@ public:
      * @return A valid reference to the object in the context of the registry.
      */
     template<typename Type>
-    const Type & ctx() const {
+    [[nodiscard]] const Type & ctx() const {
         const auto *instance = try_ctx<Type>();
         ENTT_ASSERT(instance);
         return *instance;
@@ -1646,7 +1647,7 @@ public:
 
     /*! @copydoc ctx */
     template<typename Type>
-    Type & ctx() {
+    [[nodiscard]] Type & ctx() {
         return const_cast<Type &>(std::as_const(*this).template ctx<Type>());
     }
 

src/entt/entity/runtime_view.hpp

@@ -74,7 +74,7 @@ class basic_runtime_view {
             }
         }
 
-        bool valid() const {
+        [[nodiscard]] bool valid() const {
             return std::all_of(pools->begin()++, pools->end(), [entt = *it](const auto *curr) {
                 return curr->contains(entt);
             });
@@ -109,19 +109,19 @@ class basic_runtime_view {
             return operator--(), orig;
         }
 
-        bool operator==(const view_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator==(const view_iterator &other) const ENTT_NOEXCEPT {
             return other.it == it;
         }
 
-        bool operator!=(const view_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator!=(const view_iterator &other) const ENTT_NOEXCEPT {
             return !(*this == other);
         }
 
-        pointer operator->() const {
+        [[nodiscard]] pointer operator->() const {
             return it.operator->();
         }
 
-        reference operator*() const {
+        [[nodiscard]] reference operator*() const {
             return *operator->();
         }
 
@@ -141,7 +141,7 @@ class basic_runtime_view {
         std::rotate(pools.begin(), it, pools.end());
     }
 
-    bool valid() const {
+    [[nodiscard]] bool valid() const {
         return !pools.empty() && pools.front();
     }
 
@@ -157,7 +157,7 @@ public:
      * @brief Estimates the number of entities that have the given components.
      * @return Estimated number of entities that have the given components.
      */
-    size_type size() const {
+    [[nodiscard]] size_type size() const {
         return valid() ? pools.front()->size() : size_type{};
     }
 
@@ -165,7 +165,7 @@ public:
      * @brief Checks if the view is definitely empty.
      * @return True if the view is definitely empty, false otherwise.
      */
-    bool empty() const {
+    [[nodiscard]] bool empty() const {
         return !valid() || pools.front()->empty();
     }
 
@@ -183,7 +183,7 @@ public:
      *
      * @return An iterator to the first entity that has the given components.
      */
-    iterator begin() const {
+    [[nodiscard]] iterator begin() const {
         iterator it{};
 
         if(valid()) {
@@ -208,7 +208,7 @@ public:
      * @return An iterator to the entity following the last entity that has the
      * given components.
      */
-    iterator end() const {
+    [[nodiscard]] iterator end() const {
         iterator it{};
 
         if(valid()) {
@@ -223,7 +223,7 @@ public:
      * @param entt A valid entity identifier.
      * @return True if the view contains the given entity, false otherwise.
      */
-    bool contains(const entity_type entt) const {
+    [[nodiscard]] bool contains(const entity_type entt) const {
         return valid() && std::all_of(pools.cbegin(), pools.cend(), [entt](const auto *view) {
             return view->find(entt) != view->end();
         });

src/entt/entity/snapshot.hpp

@@ -533,7 +533,7 @@ public:
      * @param entt An entity identifier.
      * @return True if `entity` is managed by the loader, false otherwise.
      */
-    bool contains(entity_type entt) const ENTT_NOEXCEPT {
+    [[nodiscard]] bool contains(entity_type entt) const ENTT_NOEXCEPT {
         return (remloc.find(entt) != remloc.cend());
     }
 
@@ -542,7 +542,7 @@ public:
      * @param entt An entity identifier.
      * @return The local identifier if any, the null entity otherwise.
      */
-    entity_type map(entity_type entt) const ENTT_NOEXCEPT {
+    [[nodiscard]] entity_type map(entity_type entt) const ENTT_NOEXCEPT {
         const auto it = remloc.find(entt);
         entity_type other = null;
 

src/entt/entity/sparse_set.hpp

@@ -106,41 +106,41 @@ class sparse_set {
             return other.index - index;
         }
 
-        reference operator[](const difference_type value) const {
+        [[nodiscard]] reference operator[](const difference_type value) const {
             const auto pos = size_type(index-value-1);
             return (*packed)[pos];
         }
 
-        bool operator==(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator==(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
             return other.index == index;
         }
 
-        bool operator!=(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator!=(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
             return !(*this == other);
         }
 
-        bool operator<(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator<(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
             return index > other.index;
         }
 
-        bool operator>(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator>(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
             return index < other.index;
         }
 
-        bool operator<=(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator<=(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
             return !(*this > other);
         }
 
-        bool operator>=(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator>=(const sparse_set_iterator &other) const ENTT_NOEXCEPT {
             return !(*this < other);
         }
 
-        pointer operator->() const {
+        [[nodiscard]] pointer operator->() const {
             const auto pos = size_type(index-1);
             return &(*packed)[pos];
         }
 
-        reference operator*() const {
+        [[nodiscard]] reference operator*() const {
             return *operator->();
         }
 
@@ -149,15 +149,15 @@ class sparse_set {
         index_type index;
     };
 
-    auto page(const Entity entt) const ENTT_NOEXCEPT {
+    [[nodiscard]] auto page(const Entity entt) const ENTT_NOEXCEPT {
         return std::size_t{(to_integral(entt) & traits_type::entity_mask) / entt_per_page};
     }
 
-    auto offset(const Entity entt) const ENTT_NOEXCEPT {
+    [[nodiscard]] auto offset(const Entity entt) const ENTT_NOEXCEPT {
         return std::size_t{to_integral(entt) & (entt_per_page - 1)};
     }
 
-    page_type & assure(const std::size_t pos) {
+    [[nodiscard]] page_type & assure(const std::size_t pos) {
         if(!(pos < sparse.size())) {
             sparse.resize(pos+1);
         }
@@ -210,7 +210,7 @@ public:
      * allocated space for.
      * @return Capacity of the sparse set.
      */
-    size_type capacity() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type capacity() const ENTT_NOEXCEPT {
         return packed.capacity();
     }
 
@@ -235,7 +235,7 @@ public:
      *
      * @return Extent of the sparse set.
      */
-    size_type extent() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type extent() const ENTT_NOEXCEPT {
         return sparse.size() * entt_per_page;
     }
 
@@ -249,7 +249,7 @@ public:
      *
      * @return Number of elements.
      */
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return packed.size();
     }
 
@@ -257,7 +257,7 @@ public:
      * @brief Checks whether a sparse set is empty.
      * @return True if the sparse set is empty, false otherwise.
      */
-    bool empty() const ENTT_NOEXCEPT {
+    [[nodiscard]] bool empty() const ENTT_NOEXCEPT {
         return packed.empty();
     }
 
@@ -273,7 +273,7 @@ public:
      *
      * @return A pointer to the internal packed array.
      */
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return packed.data();
     }
 
@@ -290,7 +290,7 @@ public:
      *
      * @return An iterator to the first entity of the internal packed array.
      */
-    iterator begin() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
         const typename traits_type::difference_type pos = packed.size();
         return iterator{packed, pos};
     }
@@ -309,7 +309,7 @@ public:
      * @return An iterator to the element following the last entity of the
      * internal packed array.
      */
-    iterator end() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator end() const ENTT_NOEXCEPT {
         return iterator{packed, {}};
     }
 
@@ -319,7 +319,7 @@ public:
      * @return An iterator to the given entity if it's found, past the end
      * iterator otherwise.
      */
-    iterator find(const entity_type entt) const {
+    [[nodiscard]] iterator find(const entity_type entt) const {
         return contains(entt) ? --(end() - index(entt)) : end();
     }
 
@@ -328,7 +328,7 @@ public:
      * @param entt A valid entity identifier.
      * @return True if the sparse set contains the entity, false otherwise.
      */
-    bool contains(const entity_type entt) const {
+    [[nodiscard]] bool contains(const entity_type entt) const {
         const auto curr = page(entt);
         // testing against null permits to avoid accessing the packed array
         return (curr < sparse.size() && sparse[curr] && sparse[curr][offset(entt)] != null);
@@ -346,7 +346,7 @@ public:
      * @param entt A valid entity identifier.
      * @return The position of the entity in the sparse set.
      */
-    size_type index(const entity_type entt) const {
+    [[nodiscard]] size_type index(const entity_type entt) const {
         ENTT_ASSERT(contains(entt));
         return size_type(sparse[page(entt)][offset(entt)]);
     }

src/entt/entity/storage.hpp

@@ -111,41 +111,41 @@ class storage: public sparse_set<Entity> {
             return other.index - index;
         }
 
-        reference operator[](const difference_type value) const ENTT_NOEXCEPT {
+        [[nodiscard]] reference operator[](const difference_type value) const ENTT_NOEXCEPT {
             const auto pos = size_type(index-value-1);
             return (*instances)[pos];
         }
 
-        bool operator==(const storage_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator==(const storage_iterator &other) const ENTT_NOEXCEPT {
             return other.index == index;
         }
 
-        bool operator!=(const storage_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator!=(const storage_iterator &other) const ENTT_NOEXCEPT {
             return !(*this == other);
         }
 
-        bool operator<(const storage_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator<(const storage_iterator &other) const ENTT_NOEXCEPT {
             return index > other.index;
         }
 
-        bool operator>(const storage_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator>(const storage_iterator &other) const ENTT_NOEXCEPT {
             return index < other.index;
         }
 
-        bool operator<=(const storage_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator<=(const storage_iterator &other) const ENTT_NOEXCEPT {
             return !(*this > other);
         }
 
-        bool operator>=(const storage_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator>=(const storage_iterator &other) const ENTT_NOEXCEPT {
             return !(*this < other);
         }
 
-        pointer operator->() const ENTT_NOEXCEPT {
+        [[nodiscard]] pointer operator->() const ENTT_NOEXCEPT {
             const auto pos = size_type(index-1);
             return &(*instances)[pos];
         }
 
-        reference operator*() const ENTT_NOEXCEPT {
+        [[nodiscard]] reference operator*() const ENTT_NOEXCEPT {
             return *operator->();
         }
 
@@ -197,12 +197,12 @@ public:
      *
      * @return A pointer to the array of objects.
      */
-    const object_type * raw() const ENTT_NOEXCEPT {
+    [[nodiscard]] const object_type * raw() const ENTT_NOEXCEPT {
         return instances.data();
     }
 
     /*! @copydoc raw */
-    object_type * raw() ENTT_NOEXCEPT {
+    [[nodiscard]] object_type * raw() ENTT_NOEXCEPT {
         return const_cast<object_type *>(std::as_const(*this).raw());
     }
 
@@ -218,18 +218,18 @@ public:
      *
      * @return An iterator to the first instance of the given type.
      */
-    const_iterator cbegin() const ENTT_NOEXCEPT {
+    [[nodiscard]] const_iterator cbegin() const ENTT_NOEXCEPT {
         const typename traits_type::difference_type pos = underlying_type::size();
         return const_iterator{instances, pos};
     }
 
     /*! @copydoc cbegin */
-    const_iterator begin() const ENTT_NOEXCEPT {
+    [[nodiscard]] const_iterator begin() const ENTT_NOEXCEPT {
         return cbegin();
     }
 
     /*! @copydoc begin */
-    iterator begin() ENTT_NOEXCEPT {
+    [[nodiscard]] iterator begin() ENTT_NOEXCEPT {
         const typename traits_type::difference_type pos = underlying_type::size();
         return iterator{instances, pos};
     }
@@ -248,17 +248,17 @@ public:
      * @return An iterator to the element following the last instance of the
      * given type.
      */
-    const_iterator cend() const ENTT_NOEXCEPT {
+    [[nodiscard]] const_iterator cend() const ENTT_NOEXCEPT {
         return const_iterator{instances, {}};
     }
 
     /*! @copydoc cend */
-    const_iterator end() const ENTT_NOEXCEPT {
+    [[nodiscard]] const_iterator end() const ENTT_NOEXCEPT {
         return cend();
     }
 
     /*! @copydoc end */
-    iterator end() ENTT_NOEXCEPT {
+    [[nodiscard]] iterator end() ENTT_NOEXCEPT {
         return iterator{instances, {}};
     }
 
@@ -274,12 +274,12 @@ public:
      * @param entt A valid entity identifier.
      * @return The object associated with the entity.
      */
-    const object_type & get(const entity_type entt) const {
+    [[nodiscard]] const object_type & get(const entity_type entt) const {
         return instances[underlying_type::index(entt)];
     }
 
     /*! @copydoc get */
-    object_type & get(const entity_type entt) {
+    [[nodiscard]] object_type & get(const entity_type entt) {
         return const_cast<object_type &>(std::as_const(*this).get(entt));
     }
 
@@ -288,12 +288,12 @@ public:
      * @param entt A valid entity identifier.
      * @return The object associated with the entity, if any.
      */
-    const object_type * try_get(const entity_type entt) const {
+    [[nodiscard]] const object_type * try_get(const entity_type entt) const {
         return underlying_type::contains(entt) ? (instances.data() + underlying_type::index(entt)) : nullptr;
     }
 
     /*! @copydoc try_get */
-    object_type * try_get(const entity_type entt) {
+    [[nodiscard]] object_type * try_get(const entity_type entt) {
         return const_cast<object_type *>(std::as_const(*this).try_get(entt));
     }
 

src/entt/entity/view.hpp

@@ -101,7 +101,7 @@ class basic_view<Entity, exclude_t<Exclude...>, Component...> {
             }
         }
 
-        bool valid() const {
+        [[nodiscard]] bool valid() const {
             return std::all_of(unchecked.cbegin(), unchecked.cend(), [entt = *it](const sparse_set<Entity> *curr) { return curr->contains(entt); })
                     && std::none_of(filter.cbegin(), filter.cend(), [entt = *it](const sparse_set<Entity> *curr) { return curr->contains(entt); });
         }
@@ -135,19 +135,19 @@ class basic_view<Entity, exclude_t<Exclude...>, Component...> {
             return operator--(), orig;
         }
 
-        bool operator==(const view_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator==(const view_iterator &other) const ENTT_NOEXCEPT {
             return other.it == it;
         }
 
-        bool operator!=(const view_iterator &other) const ENTT_NOEXCEPT {
+        [[nodiscard]] bool operator!=(const view_iterator &other) const ENTT_NOEXCEPT {
             return !(*this == other);
         }
 
-        pointer operator->() const {
+        [[nodiscard]] pointer operator->() const {
             return it.operator->();
         }
 
-        reference operator*() const {
+        [[nodiscard]] reference operator*() const {
             return *operator->();
         }
 
@@ -162,13 +162,13 @@ class basic_view<Entity, exclude_t<Exclude...>, Component...> {
         : pools{&component..., &epool...}
     {}
 
-    const sparse_set<Entity> & candidate() const ENTT_NOEXCEPT {
+    [[nodiscard]] const sparse_set<Entity> & candidate() const ENTT_NOEXCEPT {
         return *std::min({ static_cast<const sparse_set<Entity> *>(std::get<pool_type<Component> *>(pools))... }, [](const auto *lhs, const auto *rhs) {
             return lhs->size() < rhs->size();
         });
     }
 
-    unchecked_type unchecked(const sparse_set<Entity> &view) const {
+    [[nodiscard]] unchecked_type unchecked(const sparse_set<Entity> &view) const {
         std::size_t pos{};
         unchecked_type other{};
         ((std::get<pool_type<Component> *>(pools) == &view ? nullptr : (other[pos++] = std::get<pool_type<Component> *>(pools))), ...);
@@ -176,7 +176,7 @@ class basic_view<Entity, exclude_t<Exclude...>, Component...> {
     }
 
     template<typename Comp, typename Other>
-    decltype(auto) get([[maybe_unused]] component_iterator<Comp> it, [[maybe_unused]] pool_type<Other> *cpool, [[maybe_unused]] const Entity entt) const {
+    [[nodiscard]] decltype(auto) get([[maybe_unused]] component_iterator<Comp> it, [[maybe_unused]] pool_type<Other> *cpool, [[maybe_unused]] const Entity entt) const {
         if constexpr(std::is_same_v<Comp, Other>) {
             return *it;
         } else {
@@ -230,7 +230,7 @@ public:
      * @return Number of existing components of the given type.
      */
     template<typename Comp>
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return std::get<pool_type<Comp> *>(pools)->size();
     }
 
@@ -238,7 +238,7 @@ public:
      * @brief Estimates the number of entities iterated by the view.
      * @return Estimated number of entities iterated by the view.
      */
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return std::min({ std::get<pool_type<Component> *>(pools)->size()... });
     }
 
@@ -253,7 +253,7 @@ public:
      * @return True if the view or the pools are empty, false otherwise.
      */
     template<typename... Comp>
-    bool empty() const ENTT_NOEXCEPT {
+    [[nodiscard]] bool empty() const ENTT_NOEXCEPT {
         if constexpr(sizeof...(Comp) == 0) {
             return (std::get<pool_type<Component> *>(pools)->empty() || ...);
         } else {
@@ -276,7 +276,7 @@ public:
      * @return A pointer to the array of components.
      */
     template<typename Comp>
-    Comp * raw() const ENTT_NOEXCEPT {
+    [[nodiscard]] Comp * raw() const ENTT_NOEXCEPT {
         return std::get<pool_type<Comp> *>(pools)->raw();
     }
 
@@ -295,7 +295,7 @@ public:
      * @return A pointer to the array of entities.
      */
     template<typename Comp>
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return std::get<pool_type<Comp> *>(pools)->data();
     }
 
@@ -313,7 +313,7 @@ public:
      *
      * @return An iterator to the first entity that has the given components.
      */
-    iterator begin() const {
+    [[nodiscard]] iterator begin() const {
         const auto &view = candidate();
         const filter_type ignore{std::get<pool_type<Exclude> *>(pools)...};
         return iterator{view, unchecked(view), ignore, view.begin()};
@@ -334,7 +334,7 @@ public:
      * @return An iterator to the entity following the last entity that has the
      * given components.
      */
-    iterator end() const {
+    [[nodiscard]] iterator end() const {
         const auto &view = candidate();
         const filter_type ignore{std::get<pool_type<Exclude> *>(pools)...};
         return iterator{view, unchecked(view), ignore, view.end()};
@@ -345,7 +345,7 @@ public:
      * @return The first entity that has the given components if one exists, the
      * null entity otherwise.
      */
-    entity_type front() const {
+    [[nodiscard]] entity_type front() const {
         const auto it = begin();
         return it != end() ? *it : null;
     }
@@ -355,7 +355,7 @@ public:
      * @return The last entity that has the given components if one exists, the
      * null entity otherwise.
      */
-    entity_type back() const {
+    [[nodiscard]] entity_type back() const {
         const auto it = std::make_reverse_iterator(end());
         return it != std::make_reverse_iterator(begin()) ? *it : null;
     }
@@ -366,7 +366,7 @@ public:
      * @return An iterator to the given entity if it's found, past the end
      * iterator otherwise.
      */
-    iterator find(const entity_type entt) const {
+    [[nodiscard]] iterator find(const entity_type entt) const {
         const auto &view = candidate();
         const filter_type ignore{std::get<pool_type<Exclude> *>(pools)...};
         iterator it{view, unchecked(view), ignore, view.find(entt)};
@@ -378,7 +378,7 @@ public:
      * @param entt A valid entity identifier.
      * @return True if the view contains the given entity, false otherwise.
      */
-    bool contains(const entity_type entt) const {
+    [[nodiscard]] bool contains(const entity_type entt) const {
         return (std::get<pool_type<Component> *>(pools)->contains(entt) && ...)
                 && (!std::get<pool_type<Exclude> *>(pools)->contains(entt) && ...);
     }
@@ -401,7 +401,7 @@ public:
      * @return The components assigned to the entity.
      */
     template<typename... Comp>
-    decltype(auto) get([[maybe_unused]] const entity_type entt) const {
+    [[nodiscard]] decltype(auto) get([[maybe_unused]] const entity_type entt) const {
         ENTT_ASSERT(contains(entt));
 
         if constexpr(sizeof...(Comp) == 0) {
@@ -525,7 +525,7 @@ public:
      * @brief Returns the number of entities that have the given component.
      * @return Number of entities that have the given component.
      */
-    size_type size() const ENTT_NOEXCEPT {
+    [[nodiscard]] size_type size() const ENTT_NOEXCEPT {
         return pool->size();
     }
 
@@ -533,7 +533,7 @@ public:
      * @brief Checks whether a view is empty.
      * @return True if the view is empty, false otherwise.
      */
-    bool empty() const ENTT_NOEXCEPT {
+    [[nodiscard]] bool empty() const ENTT_NOEXCEPT {
         return pool->empty();
     }
 
@@ -549,7 +549,7 @@ public:
      *
      * @return A pointer to the array of components.
      */
-    raw_type * raw() const ENTT_NOEXCEPT {
+    [[nodiscard]] raw_type * raw() const ENTT_NOEXCEPT {
         return pool->raw();
     }
 
@@ -565,7 +565,7 @@ public:
      *
      * @return A pointer to the array of entities.
      */
-    const entity_type * data() const ENTT_NOEXCEPT {
+    [[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
         return pool->data();
     }
 
@@ -583,7 +583,7 @@ public:
      *
      * @return An iterator to the first entity that has the given component.
      */
-    iterator begin() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
         return pool->sparse_set<Entity>::begin();
     }
 
@@ -602,7 +602,7 @@ public:
      * @return An iterator to the entity following the last entity that has the
      * given component.
      */
-    iterator end() const ENTT_NOEXCEPT {
+    [[nodiscard]] iterator end() const ENTT_NOEXCEPT {
         return pool->sparse_set<Entity>::end();
     }
 
@@ -611,7 +611,7 @@ public:
      * @return The first entity that has the given component if one exists, the
      * null entity otherwise.
      */
-    entity_type front() const {
+    [[nodiscard]] entity_type front() const {
         const auto it = begin();
         return it != end() ? *it : null;
     }
@@ -621,7 +621,7 @@ public:
      * @return The last entity that has the given component if one exists, the
      * null entity otherwise.
      */
-    entity_type back() const {
+    [[nodiscard]] entity_type back() const {
         const auto it = std::make_reverse_iterator(end());
         return it != std::make_reverse_iterator(begin()) ? *it : null;
     }
@@ -632,7 +632,7 @@ public:
      * @return An iterator to the given entity if it's found, past the end
      * iterator otherwise.
      */
-    iterator find(const entity_type entt) const {
+    [[nodiscard]] iterator find(const entity_type entt) const {
         const auto it = pool->find(entt);
         return it != end() && *it == entt ? it : end();
     }
@@ -642,7 +642,7 @@ public:
      * @param pos Position of the element to return.
      * @return The identifier that occupies the given position.
      */
-    entity_type operator[](const size_type pos) const {
+    [[nodiscard]] entity_type operator[](const size_type pos) const {
         return begin()[pos];
     }
 
@@ -651,7 +651,7 @@ public:
      * @param entt A valid entity identifier.
      * @return True if the view contains the given entity, false otherwise.
      */
-    bool contains(const entity_type entt) const {
+    [[nodiscard]] bool contains(const entity_type entt) const {
         return pool->contains(entt);
     }
 
@@ -671,7 +671,7 @@ public:
      * @return The component assigned to the entity.
      */
     template<typename Comp = Component>
-    decltype(auto) get(const entity_type entt) const {
+    [[nodiscard]] decltype(auto) get(const entity_type entt) const {
         static_assert(std::is_same_v<Comp, Component>, "Invalid component type");
         ENTT_ASSERT(contains(entt));
         return pool->get(entt);

test/benchmark/benchmark.cpp

@@ -148,7 +148,7 @@ TEST(Benchmark, IterateSingleComponent1M) {
         registry.emplace<position>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position>().each(func);
         timer.elapsed();
@@ -169,7 +169,7 @@ TEST(Benchmark, IterateSingleComponentRuntime1M) {
         registry.emplace<position>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = { entt::type_info<position>::id() };
 
         timer timer;
@@ -193,7 +193,7 @@ TEST(Benchmark, IterateTwoComponents1M) {
         registry.emplace<velocity>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity>().each(func);
         timer.elapsed();
@@ -218,7 +218,7 @@ TEST(Benchmark, IterateTwoComponents1MHalf) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity>().each(func);
         timer.elapsed();
@@ -243,7 +243,7 @@ TEST(Benchmark, IterateTwoComponents1MOne) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity>().each(func);
         timer.elapsed();
@@ -256,7 +256,7 @@ TEST(Benchmark, IterateTwoComponents1MOne) {
 
 TEST(Benchmark, IterateTwoComponentsNonOwningGroup1M) {
     entt::registry registry;
-    registry.group<>(entt::get<position, velocity>);
+    const auto group = registry.group<>(entt::get<position, velocity>);
 
     std::cout << "Iterating over 1000000 entities, two components, non owning group" << std::endl;
 
@@ -266,9 +266,9 @@ TEST(Benchmark, IterateTwoComponentsNonOwningGroup1M) {
         registry.emplace<velocity>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<>(entt::get<position, velocity>).each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -279,7 +279,7 @@ TEST(Benchmark, IterateTwoComponentsNonOwningGroup1M) {
 
 TEST(Benchmark, IterateTwoComponentsFullOwningGroup1M) {
     entt::registry registry;
-    registry.group<position, velocity>();
+    const auto group = registry.group<position, velocity>();
 
     std::cout << "Iterating over 1000000 entities, two components, full owning group" << std::endl;
 
@@ -289,9 +289,9 @@ TEST(Benchmark, IterateTwoComponentsFullOwningGroup1M) {
         registry.emplace<velocity>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<position, velocity>().each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -302,7 +302,7 @@ TEST(Benchmark, IterateTwoComponentsFullOwningGroup1M) {
 
 TEST(Benchmark, IterateTwoComponentsPartialOwningGroup1M) {
     entt::registry registry;
-    registry.group<position>(entt::get<velocity>);
+    const auto group = registry.group<position>(entt::get<velocity>);
 
     std::cout << "Iterating over 1000000 entities, two components, partial owning group" << std::endl;
 
@@ -312,9 +312,9 @@ TEST(Benchmark, IterateTwoComponentsPartialOwningGroup1M) {
         registry.emplace<velocity>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<position>(entt::get<velocity>).each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -334,7 +334,7 @@ TEST(Benchmark, IterateTwoComponentsRuntime1M) {
         registry.emplace<velocity>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id()
@@ -365,7 +365,7 @@ TEST(Benchmark, IterateTwoComponentsRuntime1MHalf) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id()
@@ -396,7 +396,7 @@ TEST(Benchmark, IterateTwoComponentsRuntime1MOne) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id()
@@ -425,7 +425,7 @@ TEST(Benchmark, IterateThreeComponents1M) {
         registry.emplace<comp<0>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity, comp<0>>().each(func);
         timer.elapsed();
@@ -451,7 +451,7 @@ TEST(Benchmark, IterateThreeComponents1MHalf) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity, comp<0>>().each(func);
         timer.elapsed();
@@ -477,7 +477,7 @@ TEST(Benchmark, IterateThreeComponents1MOne) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity, comp<0>>().each(func);
         timer.elapsed();
@@ -490,7 +490,7 @@ TEST(Benchmark, IterateThreeComponents1MOne) {
 
 TEST(Benchmark, IterateThreeComponentsNonOwningGroup1M) {
     entt::registry registry;
-    registry.group<>(entt::get<position, velocity, comp<0>>);
+    const auto group = registry.group<>(entt::get<position, velocity, comp<0>>);
 
     std::cout << "Iterating over 1000000 entities, three components, non owning group" << std::endl;
 
@@ -501,9 +501,9 @@ TEST(Benchmark, IterateThreeComponentsNonOwningGroup1M) {
         registry.emplace<comp<0>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<>(entt::get<position, velocity, comp<0>>).each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -514,7 +514,7 @@ TEST(Benchmark, IterateThreeComponentsNonOwningGroup1M) {
 
 TEST(Benchmark, IterateThreeComponentsFullOwningGroup1M) {
     entt::registry registry;
-    registry.group<position, velocity, comp<0>>();
+    const auto group = registry.group<position, velocity, comp<0>>();
 
     std::cout << "Iterating over 1000000 entities, three components, full owning group" << std::endl;
 
@@ -525,9 +525,9 @@ TEST(Benchmark, IterateThreeComponentsFullOwningGroup1M) {
         registry.emplace<comp<0>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<position, velocity, comp<0>>().each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -538,7 +538,7 @@ TEST(Benchmark, IterateThreeComponentsFullOwningGroup1M) {
 
 TEST(Benchmark, IterateThreeComponentsPartialOwningGroup1M) {
     entt::registry registry;
-    registry.group<position, velocity>(entt::get<comp<0>>);
+    const auto group = registry.group<position, velocity>(entt::get<comp<0>>);
 
     std::cout << "Iterating over 1000000 entities, three components, partial owning group" << std::endl;
 
@@ -549,9 +549,9 @@ TEST(Benchmark, IterateThreeComponentsPartialOwningGroup1M) {
         registry.emplace<comp<0>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<position, velocity>(entt::get<comp<0>>).each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -572,7 +572,7 @@ TEST(Benchmark, IterateThreeComponentsRuntime1M) {
         registry.emplace<comp<0>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id(),
@@ -606,7 +606,7 @@ TEST(Benchmark, IterateThreeComponentsRuntime1MHalf) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id(),
@@ -640,7 +640,7 @@ TEST(Benchmark, IterateThreeComponentsRuntime1MOne) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id(),
@@ -673,7 +673,7 @@ TEST(Benchmark, IterateFiveComponents1M) {
         registry.emplace<comp<2>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity, comp<0>, comp<1>, comp<2>>().each(func);
         timer.elapsed();
@@ -701,7 +701,7 @@ TEST(Benchmark, IterateFiveComponents1MHalf) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity, comp<0>, comp<1>, comp<2>>().each(func);
         timer.elapsed();
@@ -729,7 +729,7 @@ TEST(Benchmark, IterateFiveComponents1MOne) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
         registry.view<position, velocity, comp<0>, comp<1>, comp<2>>().each(func);
         timer.elapsed();
@@ -742,7 +742,7 @@ TEST(Benchmark, IterateFiveComponents1MOne) {
 
 TEST(Benchmark, IterateFiveComponentsNonOwningGroup1M) {
     entt::registry registry;
-    registry.group<>(entt::get<position, velocity, comp<0>, comp<1>, comp<2>>);
+    const auto group = registry.group<>(entt::get<position, velocity, comp<0>, comp<1>, comp<2>>);
 
     std::cout << "Iterating over 1000000 entities, five components, non owning group" << std::endl;
 
@@ -755,9 +755,9 @@ TEST(Benchmark, IterateFiveComponentsNonOwningGroup1M) {
         registry.emplace<comp<2>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<>(entt::get<position, velocity, comp<0>, comp<1>, comp<2>>).each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -768,7 +768,7 @@ TEST(Benchmark, IterateFiveComponentsNonOwningGroup1M) {
 
 TEST(Benchmark, IterateFiveComponentsFullOwningGroup1M) {
     entt::registry registry;
-    registry.group<position, velocity, comp<0>, comp<1>, comp<2>>();
+    const auto group = registry.group<position, velocity, comp<0>, comp<1>, comp<2>>();
 
     std::cout << "Iterating over 1000000 entities, five components, full owning group" << std::endl;
 
@@ -781,9 +781,9 @@ TEST(Benchmark, IterateFiveComponentsFullOwningGroup1M) {
         registry.emplace<comp<2>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<position, velocity, comp<0>, comp<1>, comp<2>>().each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -794,7 +794,7 @@ TEST(Benchmark, IterateFiveComponentsFullOwningGroup1M) {
 
 TEST(Benchmark, IterateFiveComponentsPartialFourOfFiveOwningGroup1M) {
     entt::registry registry;
-    registry.group<position, velocity, comp<0>, comp<1>>(entt::get<comp<2>>);
+    const auto group = registry.group<position, velocity, comp<0>, comp<1>>(entt::get<comp<2>>);
 
     std::cout << "Iterating over 1000000 entities, five components, partial (4 of 5) owning group" << std::endl;
 
@@ -807,9 +807,9 @@ TEST(Benchmark, IterateFiveComponentsPartialFourOfFiveOwningGroup1M) {
         registry.emplace<comp<2>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<position, velocity, comp<0>, comp<1>>(entt::get<comp<2>>).each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -820,7 +820,7 @@ TEST(Benchmark, IterateFiveComponentsPartialFourOfFiveOwningGroup1M) {
 
 TEST(Benchmark, IterateFiveComponentsPartialThreeOfFiveOwningGroup1M) {
     entt::registry registry;
-    registry.group<position, velocity, comp<0>>(entt::get<comp<1>, comp<2>>);
+    const auto group = registry.group<position, velocity, comp<0>>(entt::get<comp<1>, comp<2>>);
 
     std::cout << "Iterating over 1000000 entities, five components, partial (3 of 5) owning group" << std::endl;
 
@@ -833,9 +833,9 @@ TEST(Benchmark, IterateFiveComponentsPartialThreeOfFiveOwningGroup1M) {
         registry.emplace<comp<2>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         timer timer;
-        registry.group<position, velocity, comp<0>>(entt::get<comp<1>, comp<2>>).each(func);
+        group.each(func);
         timer.elapsed();
     };
 
@@ -858,7 +858,7 @@ TEST(Benchmark, IterateFiveComponentsRuntime1M) {
         registry.emplace<comp<2>>(entity);
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id(),
@@ -898,7 +898,7 @@ TEST(Benchmark, IterateFiveComponentsRuntime1MHalf) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id(),
@@ -938,7 +938,7 @@ TEST(Benchmark, IterateFiveComponentsRuntime1MOne) {
         }
     }
 
-    auto test = [&registry](auto func) {
+    auto test = [&](auto func) {
         ENTT_ID_TYPE types[] = {
             entt::type_info<position>::id(),
             entt::type_info<velocity>::id(),

test/entt/entity/group.cpp

@@ -511,12 +511,12 @@ TEST(NonOwningGroup, FrontBack) {
 TEST(NonOwningGroup, SignalRace) {
     entt::registry registry;
     registry.on_construct<double>().connect<&entt::registry::emplace_or_replace<int>>();
-    registry.group(entt::get<int, double>);
+    const auto group = registry.group(entt::get<int, double>);
 
     auto entity = registry.create();
     registry.emplace<double>(entity);
 
-    ASSERT_EQ(registry.group(entt::get<int, double>).size(), 1u);
+    ASSERT_EQ(group.size(), 1u);
 }
 
 TEST(OwningGroup, Functionalities) {
@@ -1106,12 +1106,12 @@ TEST(OwningGroup, FrontBack) {
 TEST(OwningGroup, SignalRace) {
     entt::registry registry;
     registry.on_construct<double>().connect<&entt::registry::emplace_or_replace<int>>();
-    registry.group<int>(entt::get<double>);
+    const auto group = registry.group<int>(entt::get<double>);
 
     auto entity = registry.create();
     registry.emplace<double>(entity);
 
-    ASSERT_EQ(registry.group<int>(entt::get<double>).size(), 1u);
+    ASSERT_EQ(group.size(), 1u);
 }
 
 TEST(OwningGroup, StableLateInitialization) {

test/entt/entity/registry.cpp

@@ -55,7 +55,8 @@ TEST(Registry, Context) {
 
     registry.set<char>();
     registry.set<int>();
-    registry.ctx_or_set<double>();
+    // suppress the warning due to the [[nodiscard]] attribute
+    static_cast<void>(registry.ctx_or_set<double>());
 
     ASSERT_NE(registry.try_ctx<char>(), nullptr);
     ASSERT_NE(registry.try_ctx<int>(), nullptr);