change item_location return from an int to item_location

src/armor_layers.cpp

@@ -774,7 +774,7 @@ void player::sort_armor()
             if( loc ) {
                 // wear the item
                 cata::optional<std::list<item>::iterator> new_equip_it =
-                    wear( this->i_at( loc.obtain( *this ) ) );
+                    wear( *loc.obtain( *this ) );
                 if( new_equip_it ) {
                     body_part bp = static_cast<body_part>( tabindex );
                     if( tabindex == num_bp || ( **new_equip_it ).covers( bp ) ) {
@@ -802,7 +802,7 @@ void player::sort_armor()
             if( loc ) {
                 // wear the item
                 if( cata::optional<std::list<item>::iterator> new_equip_it =
-                        wear( this->i_at( loc.obtain( *this ) ) ) ) {
+                        wear( *loc.obtain( *this ) ) ) {
                     // save iterator to cursor's position
                     std::list<item>::iterator cursor_it = tmp_worn[leftListIndex];
                     // reorder `worn` vector to place new item at cursor

src/avatar_action.cpp

@@ -1252,12 +1252,11 @@ void avatar_action::use_item( avatar &you, item_location &loc )
             use_in_place = true;
         } else {
             const int obtain_cost = loc.obtain_cost( you );
-            item &target = you.i_at( loc.obtain( you ) );
-            if( target.is_null() ) {
+            loc = loc.obtain( you );
+            if( !loc ) {
                 debugmsg( "Failed to obtain target item" );
                 return;
             }
-            loc = item_location( you, &target );
 
             // TODO: the following comment is inaccurate and this mechanic needs to be rexamined
             // This method only handles items in the inventory, so refund the obtain cost.
@@ -1295,7 +1294,7 @@ void avatar_action::unload( avatar &you )
 
     item *it = loc.get_item();
     if( loc.where() != item_location::type::character ) {
-        it = &you.i_at( loc.obtain( you ) );
+        it = loc.obtain( you ).get_item();
     }
     if( you.unload( *it ) ) {
         if( it->has_flag( "MAG_DESTROY" ) && it->ammo_remaining() == 0 ) {

src/game.cpp

@@ -8379,7 +8379,7 @@ void game::reload( item_location &loc, bool prompt, bool empty )
 
     bool use_loc = true;
     if( !it->has_flag( "ALLOWS_REMOTE_USE" ) ) {
-        it = &u.i_at( loc.obtain( u ) );
+        it = loc.obtain( u ).get_item();
         use_loc = false;
     }
 

src/handle_action.cpp

@@ -1206,7 +1206,7 @@ static void wear()
     item_location loc = game_menus::inv::wear( u );
 
     if( loc ) {
-        u.wear( u.i_at( loc.obtain( u ) ) );
+        u.wear( *loc.obtain( u ) );
     } else {
         add_msg( _( "Never mind." ) );
     }
@@ -1218,7 +1218,7 @@ static void takeoff()
     item_location loc = game_menus::inv::take_off( u );
 
     if( loc ) {
-        u.takeoff( u.i_at( loc.obtain( u ) ) );
+        u.takeoff( *loc.obtain( u ) );
     } else {
         add_msg( _( "Never mind." ) );
     }
@@ -1235,9 +1235,7 @@ static void read()
             item spell_book = *loc.get_item();
             spell_book.get_use( "learn_spell" )->call( u, spell_book, spell_book.active, u.pos() );
         } else {
-            // calling obtain() invalidates the item pointer
-            // TODO: find a way to do this without an int index
-            u.read( u.i_at( loc.obtain( u ) ) );
+            u.read( *loc.obtain( u ) );
         }
     } else {
         add_msg( _( "Never mind." ) );

src/item_location.cpp

@@ -74,7 +74,7 @@ class item_location::impl
         virtual type where() const = 0;
         virtual tripoint position() const = 0;
         virtual std::string describe( const Character * ) const = 0;
-        virtual int obtain( Character &, int ) = 0;
+        virtual item_location obtain( Character &, int ) = 0;
         virtual int obtain_cost( const Character &, int ) const = 0;
         virtual void remove_item() = 0;
         virtual void serialize( JsonOut &js ) const = 0;
@@ -127,9 +127,9 @@ class item_location::impl::nowhere : public item_location::impl
             return "";
         }
 
-        int obtain( Character &, int ) override {
+        item_location obtain( Character &, int ) override {
             debugmsg( "invalid use of nowhere item_location" );
-            return INT_MIN;
+            return item_location();
         }
 
         int obtain_cost( const Character &, int ) const override {
@@ -189,16 +189,16 @@ class item_location::impl::item_on_map : public item_location::impl
             return res;
         }
 
-        int obtain( Character &ch, int qty ) override {
+        item_location obtain( Character &ch, int qty ) override {
             ch.moves -= obtain_cost( ch, qty );
 
             item obj = target()->split( qty );
             if( !obj.is_null() ) {
-                return ch.get_item_position( &ch.i_add( obj, should_stack ) );
+                return item_location( ch, &ch.i_add( obj, should_stack ) );
             } else {
-                int inv = ch.get_item_position( &ch.i_add( *target(), should_stack ) );
+                item *inv = &ch.i_add( *target(), should_stack );
                 remove_item();
-                return inv;
+                return item_location( ch, inv );
             }
         }
 
@@ -307,21 +307,21 @@ class item_location::impl::item_on_person : public item_location::impl
             }
         }
 
-        int obtain( Character &ch, int qty ) override {
+        item_location obtain( Character &ch, int qty ) override {
             ch.mod_moves( -obtain_cost( ch, qty ) );
 
             if( &ch.i_at( ch.get_item_position( target() ) ) == target() ) {
                 // item already in target characters inventory at base of stack
-                return ch.get_item_position( target() );
+                return item_location( ch, target() );
             }
 
             item obj = target()->split( qty );
             if( !obj.is_null() ) {
-                return ch.get_item_position( &ch.i_add( obj, should_stack ) );
+                return item_location( ch, &ch.i_add( obj, should_stack ) );
             } else {
-                int inv = ch.get_item_position( &ch.i_add( *target(), should_stack ) );
+                item *inv = &ch.i_add( *target(), should_stack );
                 remove_item();  // This also takes off the item from whoever wears it.
-                return inv;
+                return item_location( ch, inv );
             }
         }
 
@@ -434,16 +434,16 @@ class item_location::impl::item_on_vehicle : public item_location::impl
             return res;
         }
 
-        int obtain( Character &ch, int qty ) override {
+        item_location obtain( Character &ch, int qty ) override {
             ch.moves -= obtain_cost( ch, qty );
 
             item obj = target()->split( qty );
             if( !obj.is_null() ) {
-                return ch.get_item_position( &ch.i_add( obj, should_stack ) );
+                return item_location( ch, &ch.i_add( obj, should_stack ) );
             } else {
-                int inv = ch.get_item_position( &ch.i_add( *target(), should_stack ) );
+                item *inv = &ch.i_add( *target(), should_stack );
                 remove_item();
-                return inv;
+                return item_location( ch, inv );
             }
         }
 
@@ -581,11 +581,11 @@ std::string item_location::describe( const Character *ch ) const
     return ptr->describe( ch );
 }
 
-int item_location::obtain( Character &ch, int qty )
+item_location item_location::obtain( Character &ch, int qty )
 {
     if( !ptr->valid() ) {
         debugmsg( "item location does not point to valid item" );
-        return INT_MIN;
+        return item_location();
     }
     return ptr->obtain( ch, qty );
 }

src/item_location.h

@@ -68,8 +68,8 @@ class item_location
          *  @warning caller should restack inventory if item is to remain in it
          *  @warning all further operations using this class are invalid
          *  @warning it is unsafe to call this within unsequenced operations (see #15542)
-         *  @return inventory position for the item */
-        int obtain( Character &ch, int qty = -1 );
+         *  @return item_location for the item */
+        item_location obtain( Character &ch, int qty = -1 );
 
         /** Calculate (but do not deduct) number of moves required to obtain an item
          *  @see item_location::obtain */

src/iuse_actor.cpp

@@ -2716,7 +2716,7 @@ int holster_actor::use( player &p, item &it, bool, const tripoint & ) const
             return 0;
         }
 
-        store( p, it, p.i_at( loc.obtain( p ) ) );
+        store( p, it, *loc.obtain( p ) );
     }
 
     return 0;
@@ -4186,7 +4186,7 @@ int saw_barrel_actor::use( player &p, item &it, bool t, const tripoint & ) const
         return 0;
     }
 
-    item &obj = p.i_at( loc.obtain( p ) );
+    item &obj = *loc.obtain( p );
     p.add_msg_if_player( _( "You saw down the barrel of your %s." ), obj.tname() );
     obj.contents.emplace_back( "barrel_small", calendar::turn );
 

src/npc.cpp

@@ -1009,7 +1009,7 @@ void npc::do_npc_read()
         if( !ch ) {
             return;
         }
-        item &chosen = i_at( loc.obtain( *ch ) );
+        item &chosen = *loc.obtain( *ch );
         if( can_read( chosen, fail_reasons ) ) {
             if( g->u.sees( pos() ) ) {
                 add_msg( m_info, _( "%s starts reading." ), disp_name() );