Some panics to unreachable!, better error msging

src/map_builders/area_starting_points.rs

@@ -75,7 +75,7 @@ impl AreaStartingPosition {
             }
         }
         if available_floors.is_empty() {
-            panic!("No valid floors to start on");
+            unreachable!("No valid floors to start on.");
         }
 
         available_floors.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap());

src/map_builders/forest.rs

@@ -76,7 +76,7 @@ impl RoadExit {
             }
         }
         if available_floors.is_empty() {
-            panic!("No valid floors to start on.");
+            unreachable!("No valid floors to start on.");
         }
         available_floors.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap());
         let end_x = (available_floors[0].0 as i32) % build_data.map.width;

src/map_builders/mod.rs

@@ -137,7 +137,7 @@ impl BuilderChain {
             None => {
                 self.starter = Some(starter);
             }
-            Some(_) => panic!("You can only have one starting builder."),
+            Some(_) => unreachable!("You can only have one starting builder."),
         };
     }
 
@@ -147,7 +147,7 @@ impl BuilderChain {
 
     pub fn build_map(&mut self, rng: &mut RandomNumberGenerator) {
         match &mut self.starter {
-            None => panic!("Cannot run a map builder chain without a starting build system"),
+            None => unreachable!("Cannot run a map builder chain without a starting build system"),
             Some(starter) => {
                 // Build the starting map
                 starter.build_map(rng, &mut self.build_data);

src/map_builders/room_based_spawner.rs

@@ -27,7 +27,7 @@ impl RoomBasedSpawner {
                 );
             }
         } else {
-            panic!("RoomBasedSpawner only works after rooms have been created");
+            unreachable!("RoomBasedSpawner tried to run without any rooms.");
         }
     }
 }

src/map_builders/room_based_stairs.rs

@@ -22,7 +22,7 @@ impl RoomBasedStairs {
             build_data.map.tiles[stairs_idx] = TileType::DownStair;
             build_data.take_snapshot();
         } else {
-            panic!("RoomBasedStairs only works after rooms have been created");
+            unreachable!("RoomBasedStairs tried to run without any rooms.");
         }
     }
 }

src/map_builders/room_based_starting_position.rs

@@ -20,7 +20,7 @@ impl RoomBasedStartingPosition {
             let start_pos = rooms[0].center();
             build_data.starting_position = Some(Position { x: start_pos.x, y: start_pos.y });
         } else {
-            panic!("RoomBasedStartingPosition only works after rooms have been created");
+            unreachable!("RoomBasedStartingPosition tried to run without any rooms.");
         }
     }
 }

src/map_builders/room_corner_rounding.rs

@@ -42,7 +42,7 @@ impl RoomCornerRounder {
         if let Some(rooms_builder) = &build_data.rooms {
             rooms = rooms_builder.clone();
         } else {
-            panic!("RoomCornerRounding requires a builder with rooms.");
+            unreachable!("RoomCornerRounding tried to run without any rooms.");
         }
 
         for room in rooms.iter() {

src/map_builders/room_draw.rs

@@ -50,7 +50,7 @@ impl RoomDrawer {
         if let Some(rooms_builder) = &build_data.rooms {
             rooms = rooms_builder.clone();
         } else {
-            panic!("RoomDrawer require a builder with rooms");
+            unreachable!("RoomDrawer tried to run without any rooms.");
         }
 
         for room in rooms.iter() {

src/map_builders/room_exploder.rs

@@ -20,7 +20,7 @@ impl RoomExploder {
         if let Some(rooms_builder) = &build_data.rooms {
             rooms = rooms_builder.clone();
         } else {
-            panic!("RoomExploder requires a builder with rooms.");
+            unreachable!("RoomExploder tried to run without any rooms.");
         }
         for room in rooms.iter() {
             let start = room.center();

src/map_builders/room_themer.rs

@@ -141,7 +141,7 @@ impl ThemeRooms {
         if let Some(rooms_builder) = &build_data.rooms {
             rooms = rooms_builder.clone();
         } else {
-            panic!("RoomCornerRounding requires a builder with rooms.");
+            unreachable!("RoomCornerRounding tried to run without any rooms.");
         }
 
         let count = roll_until_fail(rng, self.percent);

src/map_builders/rooms_corridors_bresenham.rs

@@ -22,7 +22,7 @@ impl BresenhamCorridors {
         if let Some(rooms_builder) = &build_data.rooms {
             rooms = rooms_builder.clone();
         } else {
-            panic!("BresenhamCorridors require a builder with room structures");
+            unreachable!("BresenhamCorridors tried to run without any rooms.");
         }
 
         let mut connected: HashSet<usize> = HashSet::new();

src/map_builders/rooms_corridors_bsp.rs

@@ -21,7 +21,7 @@ impl BspCorridors {
         if let Some(rooms_builder) = &build_data.rooms {
             rooms = rooms_builder.clone();
         } else {
-            panic!("BSP Corridors require a builder with room structures");
+            unreachable!("BSP Corridors tried to run without any rooms.");
         }
 
         let mut corridors: Vec<Vec<usize>> = Vec::new();

src/map_builders/rooms_corridors_dogleg.rs

@@ -21,7 +21,7 @@ impl DoglegCorridors {
         if let Some(rooms_builder) = &build_data.rooms {
             rooms = rooms_builder.clone();
         } else {
-            panic!("DoglegCorridors require a builder with rooms.");
+            unreachable!("DoglegCorridors tried to run without any rooms.");
         }
 
         let mut corridors: Vec<Vec<usize>> = Vec::new();

src/map_builders/rooms_corridors_nearest.rs

@@ -22,7 +22,7 @@ impl NearestCorridors {
         if let Some(rooms_builder) = &build_data.rooms {
             rooms = rooms_builder.clone();
         } else {
-            panic!("NearestCorridors requires a builder with rooms");
+            unreachable!("NearestCorridors tried to run without any rooms.");
         }
 
         let mut connected: HashSet<usize> = HashSet::new();

src/map_builders/rooms_corridors_spawner.rs

@@ -27,7 +27,7 @@ impl CorridorSpawner {
                 );
             }
         } else {
-            panic!("CorridorSpawner only works after corridors have been created");
+            unreachable!("CorridorSpawner tried to run without any corridors.");
         }
     }
 }

src/raws/rawmaster.rs

@@ -759,7 +759,7 @@ pub fn table_by_name(raws: &RawMaster, key: &str, optional_difficulty: Option<i3
 
 fn find_slot_for_equippable_item(tag: &str, raws: &RawMaster) -> EquipmentSlot {
     if !raws.item_index.contains_key(tag) {
-        panic!("Trying to equip an unknown item: {}", tag);
+        unreachable!("Tried to equip an unknown item: {}", tag);
     }
     let item_index = raws.item_index[tag];
     let item = &raws.raws.items[item_index];
@@ -794,7 +794,7 @@ fn find_slot_for_equippable_item(tag: &str, raws: &RawMaster) -> EquipmentSlot {
             }
         }
     }
-    panic!("Trying to equip {}, but it has no slot tag.", tag);
+    unreachable!("Tried to equip {}, but it has no slot tag.", tag);
 }
 
 pub fn roll_on_loot_table(
@@ -1067,7 +1067,7 @@ fn parse_damage_string(n: &str) -> (DamageType, DiceType) {
             "fire" => DamageType::Fire,
             "cold" => DamageType::Cold,
             "poison" => DamageType::Poison,
-            _ => panic!("Unrecognised damage type in raws: {}", tokens[1]),
+            _ => unreachable!("Unrecognised damage type in raws: {}", tokens[1]),
         }
     } else {
         DamageType::Physical