Convert zero-field structs to unit struct syntax

chapter-07-damage/src/components.rs

@@ -18,7 +18,7 @@ pub struct Renderable {
 }
 
 #[derive(Component, Debug)]
-pub struct Player {}
+pub struct Player;
 
 #[derive(Component)]
 pub struct Viewshed {
@@ -28,7 +28,7 @@ pub struct Viewshed {
 }
 
 #[derive(Component, Debug)]
-pub struct Monster {}
+pub struct Monster;
 
 #[derive(Component, Debug)]
 pub struct Name {
@@ -36,7 +36,7 @@ pub struct Name {
 }
 
 #[derive(Component, Debug)]
-pub struct BlocksTile {}
+pub struct BlocksTile;
 
 #[derive(Component, Debug)]
 pub struct CombatStats {

chapter-07-damage/src/damage_system.rs

@@ -3,7 +3,7 @@ use super::{CombatStats, Player, SufferDamage};
 use rltk::console;
 use specs::prelude::*;
 
-pub struct DamageSystem {}
+pub struct DamageSystem;
 
 impl<'a> System<'a> for DamageSystem {
     type SystemData = (

chapter-07-damage/src/main.rs

@@ -39,16 +39,11 @@ pub struct State {
 
 impl State {
     fn run_systems(&mut self) {
-        let mut mapindex = MapIndexingSystem {};
-        mapindex.run_now(&self.ecs);
-        let mut vis = VisibilitySystem {};
-        vis.run_now(&self.ecs);
-        let mut mob = MonsterAI {};
-        mob.run_now(&self.ecs);
-        let mut melee = MeleeCombatSystem {};
-        melee.run_now(&self.ecs);
-        let mut damage = DamageSystem {};
-        damage.run_now(&self.ecs);
+        MapIndexingSystem.run_now(&self.ecs);
+        VisibilitySystem.run_now(&self.ecs);
+        MonsterAI.run_now(&self.ecs);
+        MeleeCombatSystem.run_now(&self.ecs);
+        DamageSystem.run_now(&self.ecs);
         self.ecs.maintain();
     }
 }
@@ -130,7 +125,7 @@ fn main() {
             fg: RGB::named(rltk::YELLOW),
             bg: RGB::named(rltk::BLACK),
         })
-        .with(Player {})
+        .with(Player)
         .with(Viewshed {
             visible_tiles: Vec::new(),
             range: 8,
@@ -178,11 +173,11 @@ fn main() {
                 range: 8,
                 dirty: true,
             })
-            .with(Monster {})
+            .with(Monster)
             .with(Name {
                 name: format!("{} #{}", &name, i),
             })
-            .with(BlocksTile {})
+            .with(BlocksTile)
             .with(CombatStats {
                 max_hp: 16,
                 hp: 16,

chapter-07-damage/src/map_indexing_system.rs

@@ -2,7 +2,7 @@ extern crate specs;
 use super::{BlocksTile, Map, Position};
 use specs::prelude::*;
 
-pub struct MapIndexingSystem {}
+pub struct MapIndexingSystem;
 
 impl<'a> System<'a> for MapIndexingSystem {
     type SystemData = (

chapter-07-damage/src/melee_combat_system.rs

@@ -3,7 +3,7 @@ use super::{CombatStats, Name, SufferDamage, WantsToMelee};
 use rltk::console;
 use specs::prelude::*;
 
-pub struct MeleeCombatSystem {}
+pub struct MeleeCombatSystem;
 
 impl<'a> System<'a> for MeleeCombatSystem {
     type SystemData = (

chapter-07-damage/src/monster_ai_system.rs

@@ -4,7 +4,7 @@ use specs::prelude::*;
 extern crate rltk;
 use rltk::Point;
 
-pub struct MonsterAI {}
+pub struct MonsterAI;
 
 impl<'a> System<'a> for MonsterAI {
     #[allow(clippy::type_complexity)]

chapter-07-damage/src/visibility_system.rs

@@ -4,7 +4,7 @@ use specs::prelude::*;
 extern crate rltk;
 use rltk::{field_of_view, Point};
 
-pub struct VisibilitySystem {}
+pub struct VisibilitySystem;
 
 impl<'a> System<'a> for VisibilitySystem {
     type SystemData = (