diff --git a/.emmyrc.json b/.emmyrc.json
index 62b2e74a..c103023e 100644
--- a/.emmyrc.json
+++ b/.emmyrc.json
@@ -18,7 +18,6 @@
     },
     "$comment-disable": "Carried over from the luals config, which had these as editor only rather than checked in ci",
     "$comment-unnecessary-if": "Disabled by the config fmtk generates for itself, the api union types make it unreliable",
-    "$comment-need-check-nil": "To be enabled once the backlog is cleared, a third of it is MapPosition and BoundingBox being aliased as struct|[double, double]",
     "diagnostics": {
         "globals": [ "__DebugAdapter", "__Profiler" ],
         "disable": [
@@ -27,7 +26,6 @@
             "invert-if",
             "missing-parameter",
             "missing-return-value",
-            "need-check-nil",
             "param-type-mismatch",
             "preferred-local-alias",
             "redefined-local",
diff --git a/exp_legacy/module/expcore/roles.lua b/exp_legacy/module/expcore/roles.lua
index 529752d2..540c42ea 100644
--- a/exp_legacy/module/expcore/roles.lua
+++ b/exp_legacy/module/expcore/roles.lua
@@ -719,7 +719,7 @@ local role = Roles.new_role('Moderator', 'Mod')
 ]]
 function Roles.new_role(name, short_hand)
     ExpUtil.assert_not_runtime()
-    if Roles.config.roles[name] then return error("Role name is non unique") end
+    if Roles.config.roles[name] then error("Role name is non unique") end
     local role = setmetatable({
         name = name,
         short_hand = short_hand or name,
@@ -896,8 +896,7 @@ function Roles._prototype:set_permission_group(name, use_factorio_api)
     if use_factorio_api then
         self.permission_group = { true, name } --[[@as [boolean, string] ]]
     else
-        local group = Groups.get_group_by_name(name)
-        if not group then return end
+        assert(Groups.get_group_by_name(name), "Permission group not found: " .. name)
         self.permission_group = name
     end
     return self
diff --git a/exp_scenario/module/control/mine_depletion.lua b/exp_scenario/module/control/mine_depletion.lua
index 894c3dfb..996a6019 100644
--- a/exp_scenario/module/control/mine_depletion.lua
+++ b/exp_scenario/module/control/mine_depletion.lua
@@ -68,12 +68,13 @@ local function try_deconstruct_output_chest(entity)
     end
 
     -- Get all adjacent mining drills and inserters
+    local target_position = target.position --[[@as MapPosition.struct]]
     local entities = target.surface.find_entities_filtered{
         type = { "mining-drill", "inserter" },
         to_be_deconstructed = false,
         area = {
-            { target.position.x - 1, target.position.y - 1 },
-            { target.position.x + 1, target.position.y + 1 }
+            { target_position.x - 1, target_position.y - 1 },
+            { target_position.x + 1, target_position.y + 1 }
         },
     }
 
@@ -159,14 +160,14 @@ local function try_deconstruct_miner(entity)
     end
 
     -- Build pipes if the miner used fluid
-    local position = entity.position
+    local position = entity.position --[[@as MapPosition.struct]]
     local create_entity_position = { x = position.x, y = position.y }
     local create_entity_param = { name = "entity-ghost", inner_name = "pipe", force = entity.force, position = create_entity_position }
     local create_entity = surface.create_entity
     create_entity(create_entity_param)
 
     -- Find all the entities to connect to
-    local bounding_box = entity.bounding_box
+    local bounding_box = entity.bounding_box --[[@as ExpUtil_AABB.Box]]
     local search_area = {
         { bounding_box.left_top.x - 1, bounding_box.left_top.y - 1 },
         { bounding_box.right_bottom.x + 1, bounding_box.right_bottom.y + 1 },
@@ -246,7 +247,7 @@ local function on_resource_depleted(event)
     end
 
     -- Find all mining drills within the area
-    local position = resource.position
+    local position = resource.position --[[@as MapPosition.struct]]
     local drills = resource.surface.find_entities_filtered{
         type = "mining-drill",
         area = {
@@ -258,8 +259,9 @@ local function on_resource_depleted(event)
     -- Check which could have reached this resource
     for _, drill in pairs(drills) do
         local radius = drill.prototype.mining_drill_radius
-        local dx = math.abs(drill.position.x - position.x)
-        local dy = math.abs(drill.position.y - position.y)
+        local drill_position = drill.position --[[@as MapPosition.struct]]
+        local dx = math.abs(drill_position.x - position.x)
+        local dy = math.abs(drill_position.y - position.y)
         if dx <= radius and dy <= radius then
             try_deconstruct_miner(drill)
         end