Small improvements and updates:

- Add final to classes which should not be overridden.
- Better error loggin when dependency is missing
- Tweaks to comments

Sources/WhoopDIKit/DependencyDefinition.swift

@@ -15,7 +15,7 @@ fileprivate extension DependencyDefinition {
 }
 
 /// Provides the definition of an object factory. A fresh version of this dependency will be provide each time one is requested.
-class FactoryDefinition: DependencyDefinition {
+final class FactoryDefinition: DependencyDefinition {
     private let factory: (Any?) throws -> Any
     let serviceKey: ServiceKey
 
@@ -30,7 +30,7 @@ class FactoryDefinition: DependencyDefinition {
 }
 
 /// Provides the definition of a singleton object (i.e an object we will only create once per graph).
-class SingletonDefinition: DependencyDefinition {
+final class SingletonDefinition: DependencyDefinition {
     private let factory: (Any?) throws -> Any
     private let lock = NSLock()
     let serviceKey: ServiceKey

Sources/WhoopDIKit/ModuleList.swift

@@ -2,6 +2,6 @@ public protocol ModuleList {
     var modules: [DependencyModule] { get }
 }
 
-public class EmptyModuleList: ModuleList {
+public final class EmptyModuleList: ModuleList {
     public var modules: [DependencyModule] { [] }
 }

Sources/WhoopDIKit/ServiceDictionary.swift

@@ -1,4 +1,4 @@
-public class ServiceDictionary<Value> {
+public final class ServiceDictionary<Value> {
     private var valuesByType: [AnyHashable: Value]
 
     convenience public init() {

Sources/WhoopDIKit/WhoopDI.swift

@@ -1,4 +1,5 @@
-public class WhoopDI: DependencyRegister {
+import Foundation
+public final class WhoopDI: DependencyRegister {
     private static let serviceDict = ServiceDictionary<DependencyDefinition>()
     private static var localServiceDict: ServiceDictionary<DependencyDefinition>? = nil
 
@@ -19,6 +20,8 @@ public class WhoopDI: DependencyRegister {
         do {
             return try get(name, params)
         } catch {
+            print("Inject failed with stack trace:")
+            Thread.callStackSymbols.forEach { print($0) }
             fatalError("WhoopDI inject failed with error: \(error)")
         }
     }
@@ -52,7 +55,8 @@ public class WhoopDI: DependencyRegister {
             fatalError("Nesting WhoopDI.inject with local definitions is not currently supported")
         }
         // We need to maintain a reference to the local service dictionary because transient dependencies may also
-        // need to references dependencies from it.
+        // need to reference dependencies from it.
+        // ----
         // This is a little dangerous since we are mutating a static variable but it should be fine as long as you
         // don't use `inject { }` within the scope of another `inject { }`.
         let serviceDict = ServiceDictionary<DependencyDefinition>()

Sources/WhoopDIKit/WhoopDIValidator.swift

@@ -1,5 +1,5 @@
 /// Provides verification that the object graph is complete. This is intended to be called from within a test.
-public class WhoopDIValidator {
+public final class WhoopDIValidator {
     private let paramsDict = ServiceDictionary<Any>()
 
     public init() { }