Remove use of IUO for Encoder/Decoder State

Sources/PotentASN1/ASN1Decoder.swift

@@ -97,23 +97,22 @@ public struct ASN1DecoderTransform: InternalDecoderTransform, InternalValueDeser
 
   static func decode(_ value: ASN1, decoder: IVD) throws -> Any? {
 
-    if decoder.state == nil {
-      decoder.state = try SchemaState(initial: decoder.options.schema)
-    }
+    let state = try decoder.state ?? SchemaState(initial: decoder.options.schema)
+    decoder.state = state
 
-    let keep = zip(decoder.state.keyStack, decoder.codingPath).prefix { $0.0.stringValue == $0.1.stringValue }.count
+    let keep = zip(state.keyStack, decoder.codingPath).prefix { $0.0.stringValue == $0.1.stringValue }.count
 
-    let drop = decoder.state.count - keep
-    decoder.state.removeLast(count: drop)
+    let drop = state.count - keep
+    state.removeLast(count: drop)
 
-    for key in decoder.codingPath[decoder.state.count...] {
-      guard let container = decoder.state.container(forCodingPath: decoder.state.keyStack) else {
+    for key in decoder.codingPath[state.count...] {
+      guard let container = state.container(forCodingPath: state.keyStack) else {
         fatalError("container should already be cached")
       }
-      try decoder.state.step(into: container, key: key)
+      try state.step(into: container, key: key)
     }
 
-    return try decoder.state.decode(value)
+    return try state.decode(value)
   }
 
   public static func intercepts(_ type: Decodable.Type) -> Bool {
@@ -600,7 +599,7 @@ public struct ASN1DecoderTransform: InternalDecoderTransform, InternalValueDeser
       return nil
     }
 
-    decoder.state.save(container: UnkeyedContainer(backing: collection), forCodingPath: decoder.codingPath)
+    decoder.state?.save(container: UnkeyedContainer(backing: collection), forCodingPath: decoder.codingPath)
 
     return collection
   }
@@ -613,7 +612,7 @@ public struct ASN1DecoderTransform: InternalDecoderTransform, InternalValueDeser
       return nil
     }
 
-    decoder.state.save(container: KeyedContainer(backing: structure), forCodingPath: decoder.codingPath)
+    decoder.state?.save(container: KeyedContainer(backing: structure), forCodingPath: decoder.codingPath)
 
     return structure
   }
@@ -643,7 +642,7 @@ extension SchemaState {
     case badValue(Any, SchemaError.Context)
   }
 
-  mutating func decode(_ value: ASN1) throws -> Any? {
+  func decode(_ value: ASN1) throws -> Any? {
 
     for possibleState in currentPossibleStates {
 

Sources/PotentASN1/ASN1Encoder.swift

@@ -94,20 +94,19 @@ public struct ASN1EncoderTransform: InternalEncoderTransform, InternalValueSeria
 
   static func encode(_ value: Any?, encoder: IVE) throws -> ASN1 {
 
-    if encoder.state == nil {
-      encoder.state = try SchemaState(initial: encoder.options.schema)
-    }
+    let state = try encoder.state ?? SchemaState(initial: encoder.options.schema)
+    encoder.state = state
 
-    let keep = zip(encoder.state.keyStack, encoder.codingPath).prefix { $0.0.stringValue == $0.1.stringValue }.count
+    let keep = zip(state.keyStack, encoder.codingPath).prefix { $0.0.stringValue == $0.1.stringValue }.count
 
-    let drop = encoder.state.count - keep
-    encoder.state.removeLast(count: drop)
+    let drop = state.count - keep
+    state.removeLast(count: drop)
 
-    for key in encoder.codingPath[encoder.state.count...] {
-      try encoder.state.step(into: encoder.container(depth: encoder.state.count), key: key)
+    for key in encoder.codingPath[state.count...] {
+      try state.step(into: encoder.container(depth: state.count), key: key)
     }
 
-    return try encoder.state.encode(value)
+    return try state.encode(value)
   }
 
   public static func intercepts(_ type: Encodable.Type) -> Bool {
@@ -230,7 +229,7 @@ extension SchemaState {
     case badValue(Any, SchemaError.Context)
   }
 
-  mutating func encode(_ value: Any?) throws -> ASN1 {
+  func encode(_ value: Any?) throws -> ASN1 {
 
     guard let encoded = try tryEncode(value) else {
       let stateOptions = currentPossibleStates.map { $0.description }.joined(separator: " or ")
@@ -240,7 +239,7 @@ extension SchemaState {
     return encoded
   }
 
-  private mutating func tryEncode(_ value: Any?) throws -> ASN1? {
+  private func tryEncode(_ value: Any?) throws -> ASN1? {
 
     for possibleState in currentPossibleStates {
 
@@ -599,7 +598,7 @@ extension SchemaState {
 
 
       case .implicit(let tag, in: let tagClass, let implicitSchema):
-        var implicitSchemaState = try SchemaState(initial: implicitSchema)
+        let implicitSchemaState = try SchemaState(initial: implicitSchema)
         let encoded: ASN1
         if let taggedValue = value as? Tagged {
           guard taggedValue.tag == tag else {
@@ -620,7 +619,7 @@ extension SchemaState {
 
 
       case .explicit(let tag, in: let tagClass, let explicitSchema):
-        var explicitSchemaState = try SchemaState(initial: explicitSchema)
+        let explicitSchemaState = try SchemaState(initial: explicitSchema)
         let encoded: ASN1
         if let taggedValue = value as? Tagged {
           guard taggedValue.tag == tag else {

Sources/PotentASN1/Schema.swift

@@ -162,8 +162,7 @@ public indirect enum Schema: Equatable, Hashable {
     guard defaultValue != nil else {
       return nil
     }
-    var schemaState = try SchemaState(initial: unwrapDirectives)
-    return try schemaState.encode(nil)
+    return try SchemaState(initial: unwrapDirectives).encode(nil)
   }
 
   public var unwrapDirectives: Schema {

Sources/PotentASN1/SchemaState.swift

@@ -17,7 +17,7 @@ import PotentCodables
 ///
 /// - Note: For internal use only.
 ///
-public struct SchemaState {
+public class SchemaState {
 
   public enum SchemaError: Error {
 
@@ -77,7 +77,7 @@ public struct SchemaState {
   var currentKey: CodingKey { keyStack.last! }
   var currentPossibleStates: [State] { stateStack.last! }
 
-  mutating func removeLast(count: Int = 1) {
+  func removeLast(count: Int = 1) {
     stateStack.removeLast(count)
     keyStack.removeLast(count)
   }
@@ -86,7 +86,7 @@ public struct SchemaState {
     return containers[codingPath.map(\.stringValue)] ?? nil
   }
 
-  mutating func save(container: Any?, forCodingPath codingPath: [CodingKey]) {
+  func save(container: Any?, forCodingPath codingPath: [CodingKey]) {
     containers[codingPath.map(\.stringValue)] = container
   }
 
@@ -100,18 +100,18 @@ public struct SchemaState {
     return nil
   }
 
-  mutating func save(scope container: KeyedContainer, forCodingPath codingPath: [CodingKey]) {
+  func save(scope container: KeyedContainer, forCodingPath codingPath: [CodingKey]) {
     let path = codingPath.map(\.stringValue)
     guard !scopes.keys.contains(path) else { return }
 
     scopes[path] = Scope(container: container)
   }
 
-  mutating func removeScope(forCodingPath codingPath: [CodingKey]) {
+  func removeScope(forCodingPath codingPath: [CodingKey]) {
     scopes.removeValue(forKey: codingPath.map(\.stringValue))
   }
 
-  mutating func step(into container: Any?, key: CodingKey) throws {
+  func step(into container: Any?, key: CodingKey) throws {
     guard let currentPossibleStates = stateStack.last else { return }
 
     if let keyed = container as? KeyedContainer {

Sources/PotentCodables/ValueDecoder.swift

@@ -257,7 +257,7 @@ public class InternalValueDecoder<Value, Transform>: Decoder where Transform: In
 
   public let options: Transform.Options
 
-  public var state: Transform.State!
+  public var state: Transform.State?
 
   /// The path to the current point in encoding.
   public fileprivate(set) var codingPath: [CodingKey]

Sources/PotentCodables/ValueEncoder.swift

@@ -184,7 +184,7 @@ public class InternalValueEncoder<Value, Transform>: Encoder where Transform: In
   /// Options set on the top-level encoder.
   public let options: Transform.Options
 
-  public var state: Transform.State!
+  public var state: Transform.State?
 
   /// The path to the current point in encoding.
   public fileprivate(set) var codingPath: [CodingKey]