Config generation now uses Nullable annotations

BSIPA.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 16
-VisualStudioVersion = 16.0.28729.10
+# Visual Studio Version 17
+VisualStudioVersion = 17.1.31911.260
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "IPA", "IPA\IPA.csproj", "{14092533-98BB-40A4-9AFC-27BB75672A70}"
 	ProjectSection(ProjectDependencies) = postProject
@@ -24,7 +24,6 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		.github\workflows\docs.yml = .github\workflows\docs.yml
 		README.md = README.md
 		.github\release_draft.yml = .github\release_draft.yml
-		System.Diagnostics.CodeAnalysis.cs = System.Diagnostics.CodeAnalysis.cs
 		.github\workflows\tag_docs.yml = .github\workflows\tag_docs.yml
 	EndProjectSection
 EndProject

Common.props

@@ -14,6 +14,14 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.2" />
+    <PackageReference Include="Nullable" Version="1.3.0">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+    <PackageReference Include="IsExternalInit" Version="1.0.2">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
+    </PackageReference>
   </ItemGroup>
   
 </Project>

Common.targets

@@ -1,8 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project>
-
-  <ItemGroup>
-    <Compile Include="$(MSBuildThisFileDirectory)\System.Diagnostics.CodeAnalysis.cs"/>
-  </ItemGroup>
   
 </Project>

IPA.Loader/Config/Data/List.cs

@@ -1,4 +1,5 @@
-using IPA.Utilities;
+#nullable enable
+using IPA.Utilities;
 using System;
 using System.Collections;
 using System.Collections.Generic;
@@ -10,9 +11,9 @@ namespace IPA.Config.Data
     /// A list of <see cref="Value"/>s for serialization by an <see cref="IConfigProvider"/>.
     /// Use <see cref="Value.List"/> or <see cref="Value.From(IEnumerable{Value})"/> to create.
     /// </summary>
-    public sealed class List : Value, IList<Value>
+    public sealed class List : Value, IList<Value?>
     {
-        private readonly List<Value> values = new List<Value>();
+        private readonly List<Value?> values = new();
 
         internal List() { }
 
@@ -22,7 +23,7 @@ namespace IPA.Config.Data
         /// <param name="index">the index to retrieve the <see cref="Value"/> at</param>
         /// <returns>the <see cref="Value"/> at <paramref name="index"/></returns>
         /// <seealso cref="IList{T}.this[int]"/>
-        public Value this[int index] { get => values[index]; set => values[index] = value; }
+        public Value? this[int index] { get => values[index]; set => values[index] = value; }
 
         /// <summary>
         /// Gets the number of elements in the <see cref="List"/>.
@@ -30,21 +31,22 @@ namespace IPA.Config.Data
         /// <seealso cref="ICollection{T}.Count"/>
         public int Count => values.Count;
 
-        bool ICollection<Value>.IsReadOnly => ((IList<Value>)values).IsReadOnly;
+        bool ICollection<Value?>.IsReadOnly => ((IList<Value?>)values).IsReadOnly;
 
         /// <summary>
         /// Adds a <see cref="Value"/> to the end of this <see cref="List"/>.
         /// </summary>
         /// <param name="item">the <see cref="Value"/> to add</param>
         /// <seealso cref="ICollection{T}.Add(T)"/>
-        public void Add(Value item) => values.Add(item);
+        public void Add(Value? item) => values.Add(item);
 
         /// <summary>
         /// Adds a range of <see cref="Value"/>s to the end of this <see cref="List"/>.
         /// </summary>
         /// <param name="vals">the range of <see cref="Value"/>s to add</param>
-        public void AddRange(IEnumerable<Value> vals)
+        public void AddRange(IEnumerable<Value?> vals)
         {
+            if (vals is null) throw new ArgumentNullException(nameof(vals));
             foreach (var val in vals) Add(val);
         }
 
@@ -60,7 +62,7 @@ namespace IPA.Config.Data
         /// <param name="item">the <see cref="Value"/> to check for</param>
         /// <returns><see langword="true"/> if the item was founc, otherwise <see langword="false"/></returns>
         /// <seealso cref="ICollection{T}.Contains(T)"/>
-        public bool Contains(Value item) => values.Contains(item);
+        public bool Contains(Value? item) => values.Contains(item);
 
         /// <summary>
         /// Copies the <see cref="Value"/>s in the <see cref="List"/> to the <see cref="Array"/> in <paramref name="array"/>.
@@ -68,14 +70,14 @@ namespace IPA.Config.Data
         /// <param name="array">the <see cref="Array"/> to copy to</param>
         /// <param name="arrayIndex">the starting index to copy to</param>
         /// <seealso cref="ICollection{T}.CopyTo(T[], int)"/>
-        public void CopyTo(Value[] array, int arrayIndex) => values.CopyTo(array, arrayIndex);
+        public void CopyTo(Value?[] array, int arrayIndex) => values.CopyTo(array, arrayIndex);
 
         /// <summary>
         /// Gets an enumerator to enumerate the <see cref="List"/>.
         /// </summary>
         /// <returns>an <see cref="IEnumerator{T}"/> for this <see cref="List"/></returns>
         /// <seealso cref="IEnumerable{T}.GetEnumerator"/>
-        public IEnumerator<Value> GetEnumerator() => ((IList<Value>)values).GetEnumerator();
+        public IEnumerator<Value?> GetEnumerator() => ((IList<Value?>)values).GetEnumerator();
 
         /// <summary>
         /// Gets the index that a given <see cref="Value"/> is in the <see cref="List"/>.
@@ -83,7 +85,7 @@ namespace IPA.Config.Data
         /// <param name="item">the <see cref="Value"/> to search for</param>
         /// <returns>the index that the <paramref name="item"/> was at, or -1.</returns>
         /// <seealso cref="IList{T}.IndexOf(T)"/>
-        public int IndexOf(Value item) => values.IndexOf(item);
+        public int IndexOf(Value? item) => values.IndexOf(item);
 
         /// <summary>
         /// Inserts a <see cref="Value"/> at an index.
@@ -91,7 +93,7 @@ namespace IPA.Config.Data
         /// <param name="index">the index to insert at</param>
         /// <param name="item">the <see cref="Value"/> to insert</param>
         /// <seealso cref="IList{T}.Insert(int, T)"/>
-        public void Insert(int index, Value item) => values.Insert(index, item);
+        public void Insert(int index, Value? item) => values.Insert(index, item);
 
         /// <summary>
         /// Removes a <see cref="Value"/> from the <see cref="List"/>.
@@ -99,7 +101,7 @@ namespace IPA.Config.Data
         /// <param name="item">the <see cref="Value"/> to remove</param>
         /// <returns><see langword="true"/> if the item was removed, <see langword="false"/> otherwise</returns>
         /// <seealso cref="ICollection{T}.Remove(T)"/>
-        public bool Remove(Value item) => values.Remove(item);
+        public bool Remove(Value? item) => values.Remove(item);
 
         /// <summary>
         /// Removes a <see cref="Value"/> at an index.
@@ -115,7 +117,7 @@ namespace IPA.Config.Data
         public override string ToString()
             => $"[{string.Join(",",this.Select(v => v?.ToString() ?? "null").StrJP())}]";
 
-        IEnumerator IEnumerable.GetEnumerator() => ((IList<Value>)values).GetEnumerator();
+        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
     }
 
 

IPA.Loader/Config/Data/Map.cs

@@ -1,4 +1,5 @@
-using IPA.Utilities;
+#nullable enable
+using IPA.Utilities;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
@@ -10,10 +11,10 @@ namespace IPA.Config.Data
     /// A ordered map of <see cref="string"/> to <see cref="Value"/> for serialization by an <see cref="IConfigProvider"/>.
     /// Use <see cref="Value.Map"/> or <see cref="Value.From(IDictionary{string, Value})"/> to create.
     /// </summary>
-    public sealed class Map : Value, IDictionary<string, Value>
+    public sealed class Map : Value, IDictionary<string, Value?>
     {
-        private readonly Dictionary<string, Value> values = new Dictionary<string, Value>();
-        private readonly List<string> keyOrder = new List<string>();
+        private readonly Dictionary<string, Value?> values = new();
+        private readonly List<string> keyOrder = new();
 
         internal Map() { }
 
@@ -23,7 +24,7 @@ namespace IPA.Config.Data
         /// <param name="key">the key to get the value associated with</param>
         /// <returns>the value associated with the <paramref name="key"/></returns>
         /// <seealso cref="IDictionary{TKey, TValue}.this[TKey]"/>
-        public Value this[string key] { get => values[key]; set => values[key] = value; }
+        public Value? this[string key] { get => values[key]; set => values[key] = value; }
 
         /// <summary>
         /// Gets a collection of the keys for the <see cref="Map"/>.
@@ -39,7 +40,7 @@ namespace IPA.Config.Data
         /// guarantee that order is maintained.
         /// </remarks>
         /// <seealso cref="IDictionary{TKey, TValue}.Values"/>
-        public ICollection<Value> Values => values.Values;
+        public ICollection<Value?> Values => values.Values;
 
         /// <summary>
         /// Gets the number of key-value pairs in this <see cref="Map"/>.
@@ -47,7 +48,7 @@ namespace IPA.Config.Data
         /// <seealso cref="ICollection{T}.Count"/>
         public int Count => values.Count;
 
-        bool ICollection<KeyValuePair<string, Value>>.IsReadOnly => ((IDictionary<string, Value>)values).IsReadOnly;
+        bool ICollection<KeyValuePair<string, Value?>>.IsReadOnly => ((IDictionary<string, Value?>)values).IsReadOnly;
 
         /// <summary>
         /// Adds a new <see cref="Value"/> with a given key.
@@ -55,13 +56,13 @@ namespace IPA.Config.Data
         /// <param name="key">the key to put the value at</param>
         /// <param name="value">the <see cref="Value"/> to add</param>
         /// <seealso cref="IDictionary{TKey, TValue}.Add(TKey, TValue)"/>
-        public void Add(string key, Value value)
+        public void Add(string key, Value? value)
         {
             values.Add(key, value);
             keyOrder.Add(key);
         }
 
-        void ICollection<KeyValuePair<string, Value>>.Add(KeyValuePair<string, Value> item) 
+        void ICollection<KeyValuePair<string, Value?>>.Add(KeyValuePair<string, Value?> item) 
             => Add(item.Key, item.Value);
 
         /// <summary>
@@ -74,8 +75,8 @@ namespace IPA.Config.Data
             keyOrder.Clear();
         }
 
-        bool ICollection<KeyValuePair<string, Value>>.Contains(KeyValuePair<string, Value> item) 
-            => ((IDictionary<string, Value>)values).Contains(item);
+        bool ICollection<KeyValuePair<string, Value?>>.Contains(KeyValuePair<string, Value?> item) 
+            => ((IDictionary<string, Value?>)values).Contains(item);
 
         /// <summary>
         /// Checks if the <see cref="Map"/> contains a given <paramref name="key"/>.
@@ -85,18 +86,18 @@ namespace IPA.Config.Data
         /// <seealso cref="IDictionary{TKey, TValue}.ContainsKey(TKey)"/>
         public bool ContainsKey(string key) => values.ContainsKey(key);
 
-        void ICollection<KeyValuePair<string, Value>>.CopyTo(KeyValuePair<string, Value>[] array, int arrayIndex)
-            => ((IDictionary<string, Value>)values).CopyTo(array, arrayIndex);
+        void ICollection<KeyValuePair<string, Value?>>.CopyTo(KeyValuePair<string, Value?>[] array, int arrayIndex)
+            => ((IDictionary<string, Value?>)values).CopyTo(array, arrayIndex);
 
         /// <summary>
         /// Enumerates the <see cref="Map"/>'s key-value pairs.
         /// </summary>
         /// <returns>an <see cref="IEnumerator{T}"/> of key-value pairs in this <see cref="Map"/></returns>
         /// <seealso cref="IEnumerable{T}.GetEnumerator()"/>
-        public IEnumerator<KeyValuePair<string, Value>> GetEnumerator()
+        public IEnumerator<KeyValuePair<string, Value?>> GetEnumerator()
         {
             foreach (var key in keyOrder)
-                yield return new KeyValuePair<string, Value>(key, this[key]);
+                yield return new KeyValuePair<string, Value?>(key, this[key]);
         }
 
         /// <summary>
@@ -107,8 +108,8 @@ namespace IPA.Config.Data
         /// <seealso cref="IDictionary{TKey, TValue}.Remove(TKey)"/>
         public bool Remove(string key) => values.Remove(key) && keyOrder.Remove(key);
 
-        bool ICollection<KeyValuePair<string, Value>>.Remove(KeyValuePair<string, Value> item) 
-            => ((IDictionary<string, Value>)values).Remove(item) && (keyOrder.Remove(item.Key) || true);
+        bool ICollection<KeyValuePair<string, Value?>>.Remove(KeyValuePair<string, Value?> item) 
+            => ((IDictionary<string, Value?>)values).Remove(item) && (keyOrder.Remove(item.Key) || true);
 
         /// <summary>
         /// Gets the value associated with the specified key.
@@ -117,7 +118,7 @@ namespace IPA.Config.Data
         /// <param name="value">the target location of the retrieved object</param>
         /// <returns><see langword="true"/> if the key was found and <paramref name="value"/> set, <see langword="false"/> otherwise</returns>
         /// <seealso cref="IDictionary{TKey, TValue}.TryGetValue(TKey, out TValue)"/>
-        public bool TryGetValue(string key, out Value value) => values.TryGetValue(key, out value);
+        public bool TryGetValue(string key, out Value? value) => values.TryGetValue(key, out value);
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
 

IPA.Loader/Config/Data/Primitives.cs

@@ -1,4 +1,5 @@
-using System;
+#nullable enable
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -12,10 +13,28 @@ namespace IPA.Config.Data
     /// </summary>
     public sealed class Text : Value
     {
+        /// <summary>
+        /// Constructs an empty <see cref="Text"/> object.
+        /// </summary>
+        [Obsolete("Use the String constructor.")]
+        public Text()
+        {
+            Value = null!;
+        }
+
+        /// <summary>
+        /// Constructs a <see cref="Text"/> object containing the provided value.
+        /// </summary>
+        /// <param name="value">The value to construct with.</param>
+        public Text(string value)
+        {
+            Value = value;
+        }
+
         /// <summary>
         /// The actual value of this <see cref="Text"/> object.
         /// </summary>
-        public string Value { get; set; }
+        public string Value { get; init; }
 
         /// <summary>
         /// Converts this <see cref="Data.Value"/> into a human-readable format.
@@ -30,6 +49,24 @@ namespace IPA.Config.Data
     /// </summary>
     public sealed class Integer : Value
     {
+        /// <summary>
+        /// Constructs an empty <see cref="Integer"/> object.
+        /// </summary>
+        [Obsolete("Use the long constructor.")]
+        public Integer()
+        {
+            Value = 0;
+        }
+
+        /// <summary>
+        /// Constructs a <see cref="Integer"/> object containing the provided value.
+        /// </summary>
+        /// <param name="value">The value to construct with.</param>
+        public Integer(long value)
+        {
+            Value = value;
+        }
+
         /// <summary>
         /// The actual value of the <see cref="Integer"/> object.
         /// </summary>
@@ -50,10 +87,28 @@ namespace IPA.Config.Data
 
     /// <summary>
     /// A <see cref="Value"/> representing a floating point value. This may hold a 
-    /// <see cref="decimal"/>'s  worth of data.
+    /// <see cref="decimal"/>'s worth of data.
     /// </summary>
     public sealed class FloatingPoint : Value
     {
+        /// <summary>
+        /// Constructs an empty <see cref="FloatingPoint"/> object.
+        /// </summary>
+        [Obsolete("Use the long constructor.")]
+        public FloatingPoint()
+        {
+            Value = 0;
+        }
+
+        /// <summary>
+        /// Constructs a <see cref="FloatingPoint"/> object containing the provided value.
+        /// </summary>
+        /// <param name="value">The value to construct with.</param>
+        public FloatingPoint(decimal value)
+        {
+            Value = value;
+        }
+
         /// <summary>
         /// The actual value fo this <see cref="FloatingPoint"/> object.
         /// </summary>
@@ -76,16 +131,37 @@ namespace IPA.Config.Data
     /// A <see cref="Value"/> representing a boolean value.
     /// </summary>
     public sealed class Boolean : Value
-    {
+    {
+        /// <summary>
+        /// Constructs an empty <see cref="Boolean"/> object.
+        /// </summary>
+        [Obsolete("Use the long constructor.")]
+        public Boolean()
+        {
+            Value = false;
+        }
+
+        /// <summary>
+        /// Constructs a <see cref="Boolean"/> object containing the provided value.
+        /// </summary>
+        /// <param name="value">The value to construct with.</param>
+        public Boolean(bool value)
+        {
+            Value = value;
+        }
+
         /// <summary>
         /// The actual value fo this <see cref="Boolean"/> object.
         /// </summary>
-        public bool Value { get; set; }
-
+        public bool Value { get; set; }
+
+
         /// <summary>
         /// Converts this <see cref="Data.Value"/> into a human-readable format.
         /// </summary>
         /// <returns>the result of <c>Value.ToString().ToLower()</c></returns>
-        public override string ToString() => Value.ToString().ToLower();
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Globalization", "CA1308:Normalize strings to uppercase",
+            Justification = "ToLower is the desired display value.")]
+        public override string ToString() => Value.ToString().ToLower(System.Globalization.CultureInfo.InvariantCulture);
     }
 }

IPA.Loader/Config/Data/Value.cs

@@ -1,6 +1,8 @@
-using System;
+#nullable enable
+using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
@@ -25,21 +27,21 @@ namespace IPA.Config.Data
         /// Creates a Null <see cref="Value"/>.
         /// </summary>
         /// <returns><see langword="null"/></returns>
-        public static Value Null() => null;
+        public static Value? Null() => null;
 
         /// <summary>
         /// Creates an empty <see cref="List"/>.
         /// </summary>
         /// <returns>an empty <see cref="List"/></returns>
         /// <seealso cref="From(IEnumerable{Value})"/>
-        public static List List() => new List();
+        public static List List() => new();
         /// <summary>
         /// Creates an empty <see cref="Map"/>.
         /// </summary>
         /// <returns>an empty <see cref="Map"/></returns>
         /// <seealso cref="From(IDictionary{string, Value})"/>
         /// <seealso cref="From(IEnumerable{KeyValuePair{string, Value}})"/>
-        public static Map Map() => new Map();
+        public static Map Map() => new();
 
         /// <summary>
         /// Creates a new <see cref="Value"/> representing a <see cref="string"/>.
@@ -47,14 +49,16 @@ namespace IPA.Config.Data
         /// <param name="val">the value to wrap</param>
         /// <returns>a <see cref="Data.Text"/> wrapping <paramref name="val"/></returns>
         /// <seealso cref="Text(string)"/>
-        public static Text From(string val) => Text(val);
+        [return: NotNullIfNotNull("val")]
+        public static Text? From(string? val) => Text(val);
         /// <summary>
         /// Creates a new <see cref="Data.Text"/> object wrapping a <see cref="string"/>.
         /// </summary>
         /// <param name="val">the value to wrap</param>
         /// <returns>a <see cref="Data.Text"/> wrapping <paramref name="val"/></returns>
         /// <seealso cref="From(string)"/>
-        public static Text Text(string val) => val == null ? null : new Text { Value = val };
+        [return: NotNullIfNotNull("val")]
+        public static Text? Text(string? val) => val == null ? null : new(val);
 
         /// <summary>
         /// Creates a new <see cref="Value"/> wrapping a <see cref="long"/>.
@@ -69,7 +73,7 @@ namespace IPA.Config.Data
         /// <param name="val">the value to wrap</param>
         /// <returns>a <see cref="Data.Integer"/> wrapping <paramref name="val"/></returns>
         /// <seealso cref="From(long)"/>
-        public static Integer Integer(long val) => new Integer { Value = val };
+        public static Integer Integer(long val) => new(val);
 
         /// <summary>
         /// Creates a new <see cref="Value"/> wrapping a <see cref="double"/>.
@@ -84,7 +88,7 @@ namespace IPA.Config.Data
         /// <param name="val">the value to wrap</param>
         /// <returns>a <see cref="FloatingPoint"/> wrapping <paramref name="val"/></returns>
         /// <seealso cref="From(decimal)"/>
-        public static FloatingPoint Float(decimal val) => new FloatingPoint { Value = val };
+        public static FloatingPoint Float(decimal val) => new(val);
 
         /// <summary>
         /// Creates a new <see cref="Value"/> wrapping a <see cref="bool"/>.
@@ -99,7 +103,7 @@ namespace IPA.Config.Data
         /// <param name="val">the value to wrap</param>
         /// <returns>a <see cref="Boolean"/> wrapping <paramref name="val"/></returns>
         /// <seealso cref="From(bool)"/>
-        public static Boolean Bool(bool val) => new Boolean { Value = val };
+        public static Boolean Bool(bool val) => new(val);
 
         /// <summary>
         /// Creates a new <see cref="Data.List"/> holding the content of an <see cref="IEnumerable{T}"/>
@@ -108,9 +112,10 @@ namespace IPA.Config.Data
         /// <param name="vals">the <see cref="Value"/>s to initialize the <see cref="Data.List"/> with</param>
         /// <returns>a <see cref="Data.List"/> containing the content of <paramref name="vals"/></returns>
         /// <seealso cref="List"/>
-        public static List From(IEnumerable<Value> vals)
+        [return: NotNullIfNotNull("vals")]
+        public static List? From(IEnumerable<Value?>? vals)
         {
-            if (vals == null) return null;
+            if (vals is null) return null;
             var l = List();
             l.AddRange(vals);
             return l;
@@ -124,7 +129,7 @@ namespace IPA.Config.Data
         /// <returns>a <see cref="Data.Map"/> containing the content of <paramref name="vals"/></returns>
         /// <seealso cref="Map"/>
         /// <seealso cref="From(IEnumerable{KeyValuePair{string, Value}})"/>
-        public static Map From(IDictionary<string, Value> vals) => From(vals as IEnumerable<KeyValuePair<string, Value>>);
+        public static Map From(IDictionary<string, Value?> vals) => From(vals as IEnumerable<KeyValuePair<string, Value?>>);
 
         /// <summary>
         /// Creates a new <see cref="Data.Map"/> holding the content of an <see cref="IEnumerable{T}"/>
@@ -134,9 +139,10 @@ namespace IPA.Config.Data
         /// <returns>a <see cref="Data.Map"/> containing the content of <paramref name="vals"/></returns>
         /// <seealso cref="Map"/>
         /// <seealso cref="From(IDictionary{string, Value})"/>
-        public static Map From(IEnumerable<KeyValuePair<string, Value>> vals)
+        [return: NotNullIfNotNull("vals")]
+        public static Map? From(IEnumerable<KeyValuePair<string, Value?>>? vals)
         {
-            if (vals == null) return null;
+            if (vals is null) return null;
             var m = Map();
             foreach (var v in vals) m.Add(v.Key, v.Value);
             return m;

IPA.Loader/Config/SelfConfig.cs

@@ -175,7 +175,7 @@ namespace IPA.Config
                                      &&   CommandLineValues.YeetMods;
 
         // LINE: ignore
-        [NonNullable, UseConverter(typeof(CollectionConverter<string, HashSet<string>>))]
+        [NonNullable, UseConverter(typeof(CollectionConverter<string, HashSet<string?>>))]
         public virtual HashSet<string> GameAssemblies { get; set; } = new HashSet<string>
             {
             // LINE: ignore 5

IPA.Loader/Config/Stores/Attributes.cs

@@ -1,6 +1,8 @@
-using IPA.Config.Stores.Converters;
+#nullable enable
+using IPA.Config.Stores.Converters;
 using System;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 
 namespace IPA.Config.Stores.Attributes
@@ -37,23 +39,25 @@ namespace IPA.Config.Stores.Attributes
         /// <summary>
         /// Gets whether or not to use the default converter for the member type instead of the specified type.
         /// </summary>
+        [MemberNotNullWhen(false, nameof(ConverterType))]
         public bool UseDefaultConverterForType { get; }
 
         /// <summary>
         /// Gets the type of the converter to use.
         /// </summary>
-        public Type ConverterType { get; }
+        public Type? ConverterType { get; }
 
         /// <summary>
         /// Gets the target type of the converter if it is avaliable at instantiation time, otherwise
         /// <see langword="null"/>.
         /// </summary>
-        public Type ConverterTargetType { get; }
+        public Type? ConverterTargetType { get; }
 
         /// <summary>
         /// Gets whether or not this converter is a generic <see cref="ValueConverter{T}"/>.
         /// </summary>
-        public bool IsGenericConverter => ConverterTargetType != null;
+        [MemberNotNullWhen(true, nameof(ConverterTargetType))]
+        public bool IsGenericConverter => ConverterTargetType is not null;
 
         /// <summary>
         /// Creates a new <see cref="UseConverterAttribute"/> specifying to use the default converter type for the target member.
@@ -67,11 +71,17 @@ namespace IPA.Config.Stores.Attributes
         /// <param name="converterType">the type to assign to <see cref="ConverterType"/></param>
         public UseConverterAttribute(Type converterType)
         {
+            if (converterType is null)
+                throw new ArgumentNullException(nameof(converterType));
+
             UseDefaultConverterForType = false;
             ConverterType = converterType;
 
+            if (converterType.IsValueType)
+                throw new ArgumentException("Type is not a value converter!");
+
             var baseT = ConverterType.BaseType;
-            while (baseT != null && baseT != typeof(object) &&
+            while (baseT != typeof(object) &&
                 (!baseT.IsGenericType || baseT.GetGenericTypeDefinition() != typeof(ValueConverter<>)))
                 baseT = baseT.BaseType;
             if (baseT == typeof(object)) ConverterTargetType = null;

IPA.Loader/Config/Stores/CollectionConverter.cs

@@ -1,4 +1,5 @@
-using System;
+#nullable enable
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -14,7 +15,7 @@ namespace IPA.Config.Stores.Converters
     /// <typeparam name="T">the type of the items in the collection</typeparam>
     /// <typeparam name="TCollection">the instantiated type of collection</typeparam>
     public class CollectionConverter<T, TCollection> : ValueConverter<TCollection>
-        where TCollection : ICollection<T>
+        where TCollection : ICollection<T?>
     {
         /// <summary>
         /// Creates a <see cref="CollectionConverter{T, TCollection}"/> using the default converter for the
@@ -54,7 +55,7 @@ namespace IPA.Config.Stores.Converters
         /// <seealso cref="ValueConverter{T}.FromValue(Value, object)"/>
         protected void PopulateFromValue(TCollection col, List list, object parent)
         {
-            //Logger.log.Debug($"CollectionConverter<{typeof(T)}, {typeof(TCollection)}>({BaseConverter.GetType()}).PopulateFromValue([object], {list}, {parent.GetType()})");
+            if (list is null) throw new ArgumentNullException(nameof(list));
             foreach (var it in list)
                 col.Add(BaseConverter.FromValue(it, parent));
         }
@@ -66,9 +67,9 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the object that will own the resulting <typeparamref name="TCollection"/></param>
         /// <returns>a new <typeparamref name="TCollection"/> holding the deserialized content of <paramref name="value"/></returns>
         /// <seealso cref="ValueConverter{T}.FromValue(Value, object)"/>
-        public override TCollection FromValue(Value value, object parent)
+        public override TCollection FromValue(Value? value, object parent)
         {
-            if (!(value is List list)) throw new ArgumentException("Argument not a List", nameof(value));
+            if (value is not List list) throw new ArgumentException("Argument not a List", nameof(value));
 
             var col = Create(list.Count, parent);
             PopulateFromValue(col, list, parent);
@@ -81,7 +82,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the object owning <paramref name="obj"/></param>
         /// <returns>the <see cref="List"/> that <paramref name="obj"/> was serialized into</returns>
         /// <seealso cref="ValueConverter{T}.ToValue(T, object)"/>
-        public override Value ToValue(TCollection obj, object parent)
+        public override Value? ToValue(TCollection? obj, object parent)
             => Value.From(obj.Select(t => BaseConverter.ToValue(t, parent)));
     }
     /// <summary>
@@ -92,7 +93,7 @@ namespace IPA.Config.Stores.Converters
     /// <typeparam name="TConverter">the type of the converter to use for <typeparamref name="T"/></typeparam>
     /// <seealso cref="CollectionConverter{T, TCollection}"/>
     public sealed class CollectionConverter<T, TCollection, TConverter> : CollectionConverter<T, TCollection>
-        where TCollection : ICollection<T>
+        where TCollection : ICollection<T?>
         where TConverter : ValueConverter<T>, new()
     {
         /// <summary>
@@ -110,7 +111,7 @@ namespace IPA.Config.Stores.Converters
     /// </summary>
     /// <typeparam name="T">the element type of the <see cref="ISet{T}"/></typeparam>
     /// <seealso cref="CollectionConverter{T, TCollection}"/>
-    public class ISetConverter<T> : CollectionConverter<T, ISet<T>>
+    public class ISetConverter<T> : CollectionConverter<T, ISet<T?>>
     {
         /// <summary>
         /// Creates an <see cref="ISetConverter{T}"/> using the default converter for <typeparamref name="T"/>.
@@ -128,8 +129,8 @@ namespace IPA.Config.Stores.Converters
         /// <param name="size">the size to initialize it to</param>
         /// <param name="parent">the object that will own the new object</param>
         /// <returns>the new <see cref="ISet{T}"/></returns>
-        protected override ISet<T> Create(int size, object parent)
-            => new HashSet<T>();
+        protected override ISet<T?> Create(int size, object parent)
+            => new HashSet<T?>();
     }
     /// <summary>
     /// An <see cref="ISetConverter{T}"/> which default constructs a converter for use as the value converter.
@@ -155,7 +156,7 @@ namespace IPA.Config.Stores.Converters
     /// </summary>
     /// <typeparam name="T">the element type of the <see cref="List{T}"/></typeparam>
     /// <seealso cref="CollectionConverter{T, TCollection}"/>
-    public class ListConverter<T> : CollectionConverter<T, List<T>>
+    public class ListConverter<T> : CollectionConverter<T, List<T?>>
     {
         /// <summary>
         /// Creates an <see cref="ListConverter{T}"/> using the default converter for <typeparamref name="T"/>.
@@ -173,8 +174,8 @@ namespace IPA.Config.Stores.Converters
         /// <param name="size">the size to initialize it to</param>
         /// <param name="parent">the object that will own the new object</param>
         /// <returns>the new <see cref="List{T}"/></returns>
-        protected override List<T> Create(int size, object parent)
-            => new List<T>(size);
+        protected override List<T?> Create(int size, object parent)
+            => new(size);
     }
     /// <summary>
     /// A <see cref="ListConverter{T}"/> which default constructs a converter for use as the value converter.
@@ -199,7 +200,7 @@ namespace IPA.Config.Stores.Converters
     /// </summary>
     /// <typeparam name="T">the element type of the <see cref="IList{T}"/></typeparam>
     /// <seealso cref="CollectionConverter{T, TCollection}"/>
-    public class IListConverter<T> : CollectionConverter<T, IList<T>>
+    public class IListConverter<T> : CollectionConverter<T, IList<T?>>
     {
         /// <summary>
         /// Creates an <see cref="IListConverter{T}"/> using the default converter for <typeparamref name="T"/>.
@@ -217,8 +218,8 @@ namespace IPA.Config.Stores.Converters
         /// <param name="size">the size to initialize it to</param>
         /// <param name="parent">the object that will own the new object</param>
         /// <returns>the new <see cref="IList{T}"/></returns>
-        protected override IList<T> Create(int size, object parent)
-            => new List<T>(size);
+        protected override IList<T?> Create(int size, object parent)
+            => new List<T?>(size);
     }
     /// <summary>
     /// An <see cref="IListConverter{T}"/> which default constructs a converter for use as the value converter.

IPA.Loader/Config/Stores/Converters.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using IPA.Config.Stores.Attributes;
 using IPA.Logging;
 using System;
@@ -22,7 +23,7 @@ namespace IPA.Config.Stores.Converters
         /// </summary>
         /// <param name="val">the <see cref="Value"/> to get the integral value of</param>
         /// <returns>the integral value of <paramref name="val"/>, or <see langword="null"/></returns>
-        public static long? IntValue(Value val)
+        public static long? IntValue(Value? val)
             => val is Integer inte ? inte.Value :
                val is FloatingPoint fp ? fp.AsInteger()?.Value :
                null;
@@ -32,7 +33,7 @@ namespace IPA.Config.Stores.Converters
         /// </summary>
         /// <param name="val">the <see cref="Value"/> to get the floaing point value of</param>
         /// <returns>the floaing point value of <paramref name="val"/>, or <see langword="null"/></returns>
-        public static decimal? FloatValue(Value val)
+        public static decimal? FloatValue(Value? val)
             => val is FloatingPoint fp ? fp.Value :
                val is Integer inte ? inte.AsFloat()?.Value :
                null;
@@ -83,7 +84,7 @@ namespace IPA.Config.Stores.Converters
                 }
 
                 //Logger.log.Debug($"gives converter for value type {t}");
-                var valConv = Activator.CreateInstance(typeof(ValConv<>).MakeGenericType(t)) as IValConv;
+                var valConv = (IValConv)Activator.CreateInstance(typeof(ValConv<>).MakeGenericType(t));
                 return valConv.Get();
             }
 
@@ -117,7 +118,7 @@ namespace IPA.Config.Stores.Converters
             IValConv<DateTime>, IValConv<DateTimeOffset>,
             IValConv<TimeSpan>
         {
-            internal static readonly ValConvImpls Impl = new ValConvImpls();
+            internal static readonly ValConvImpls Impl = new();
             Type IValConv<char>.Get() => typeof(CharConverter);
             Type IValConv<long>.Get() => typeof(LongConverter);
             Type IValConv<ulong>.Get() => typeof(ULongConverter);
@@ -145,7 +146,7 @@ namespace IPA.Config.Stores.Converters
     /// <typeparam name="T">the type of the <see cref="ValueConverter{T}"/> that this works on</typeparam>
     public static class Converter<T>
     {
-        private static ValueConverter<T> defaultConverter = null;
+        private static ValueConverter<T>? defaultConverter;
         /// <summary>
         /// Gets the default <see cref="ValueConverter{T}"/> for the current type.
         /// </summary>
@@ -158,7 +159,7 @@ namespace IPA.Config.Stores.Converters
             //Logger.log.Debug($"Converter<{t}>.MakeDefault()");
 
             static ValueConverter<T> MakeInstOf(Type ty)
-                => Activator.CreateInstance(ty) as ValueConverter<T>;
+                => (ValueConverter<T>)Activator.CreateInstance(ty);
 
             return MakeInstOf(Converter.GetDefaultConverterType(t));
         }
@@ -193,16 +194,16 @@ namespace IPA.Config.Stores.Converters
         /// <param name="value">the <see cref="Value"/> tree to convert</param>
         /// <param name="parent">the object which will own the created object</param>
         /// <returns>the object represented by <paramref name="value"/></returns>
-        public override T? FromValue(Value value, object parent)
-            => value == null ? null : new T?(baseConverter.FromValue(value, parent));
+        public override T? FromValue(Value? value, object parent)
+            => value is null ? null : new T?(baseConverter.FromValue(value, parent));
         /// <summary>
         /// Converts a nullable <typeparamref name="T"/> to a <see cref="Value"/> tree.
         /// </summary>
         /// <param name="obj">the value to serialize</param>
         /// <param name="parent">the object which owns <paramref name="obj"/></param>
         /// <returns>a <see cref="Value"/> tree representing <paramref name="obj"/>.</returns>
-        public override Value ToValue(T? obj, object parent)
-            => obj == null ? null : baseConverter.ToValue(obj.Value, parent);
+        public override Value? ToValue(T? obj, object parent)
+            => obj is null ? null : baseConverter.ToValue(obj.Value, parent);
     }
 
     /// <summary>
@@ -237,7 +238,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the object which will own the created object</param>
         /// <returns>the deserialized enum value</returns>
         /// <exception cref="ArgumentException">if <paramref name="value"/> is not a <see cref="Text"/> node</exception>
-        public override T FromValue(Value value, object parent)
+        public override T FromValue(Value? value, object parent)
             => value is Text t
                 ? (T)Enum.Parse(typeof(T), t.Value)
                 : throw new ArgumentException("Value not a string", nameof(value));
@@ -248,8 +249,8 @@ namespace IPA.Config.Stores.Converters
         /// <param name="obj">the value to serialize</param>
         /// <param name="parent">the object which owns <paramref name="obj"/></param>
         /// <returns>a <see cref="Text"/> node representing <paramref name="obj"/></returns>
-        public override Value ToValue(T obj, object parent)
-            => Value.Text(obj.ToString());
+        public override Value? ToValue(T? obj, object parent)
+            => Value.Text(obj?.ToString());
     }
 
     /// <summary>
@@ -267,7 +268,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the object which will own the created object</param>
         /// <returns>the deserialized enum value</returns>
         /// <exception cref="ArgumentException">if <paramref name="value"/> is not a <see cref="Text"/> node</exception>
-        public override T FromValue(Value value, object parent)
+        public override T FromValue(Value? value, object parent)
             => value is Text t
                 ? (T)Enum.Parse(typeof(T), t.Value, true)
                 : throw new ArgumentException("Value not a string", nameof(value));
@@ -278,8 +279,8 @@ namespace IPA.Config.Stores.Converters
         /// <param name="obj">the value to serialize</param>
         /// <param name="parent">the object which owns <paramref name="obj"/></param>
         /// <returns>a <see cref="Text"/> node representing <paramref name="obj"/></returns>
-        public override Value ToValue(T obj, object parent)
-            => Value.Text(obj.ToString());
+        public override Value? ToValue(T? obj, object parent)
+            => Value.Text(obj?.ToString());
     }
 
     /// <summary>
@@ -296,7 +297,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the object which will own the created object</param>
         /// <returns>the deserialized enum value</returns>
         /// <exception cref="ArgumentException">if <paramref name="value"/> is not a numeric node</exception>
-        public override T FromValue(Value value, object parent)
+        public override T FromValue(Value? value, object parent)
             => (T)Enum.ToObject(typeof(T), Converter.IntValue(value)
                     ?? throw new ArgumentException("Value not a numeric node", nameof(value)));
 
@@ -306,7 +307,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="obj">the value to serialize</param>
         /// <param name="parent">the object which owns <paramref name="obj"/></param>
         /// <returns>an <see cref="Integer"/> node representing <paramref name="obj"/></returns>
-        public override Value ToValue(T obj, object parent)
+        public override Value ToValue(T? obj, object parent)
             => Value.Integer(Convert.ToInt64(obj));
     }
 
@@ -314,7 +315,7 @@ namespace IPA.Config.Stores.Converters
     /// A converter for instances of <see cref="IDictionary{TKey, TValue}"/>.
     /// </summary>
     /// <typeparam name="TValue">the value type of the dictionary</typeparam>
-    public class IDictionaryConverter<TValue> : ValueConverter<IDictionary<string, TValue>>
+    public class IDictionaryConverter<TValue> : ValueConverter<IDictionary<string, TValue?>>
     {
         /// <summary>
         /// Gets the converter for the dictionary's value type.
@@ -338,9 +339,9 @@ namespace IPA.Config.Stores.Converters
         /// <param name="value">the <see cref="Map"/> to convert</param>
         /// <param name="parent">the parent that will own the resulting object</param>
         /// <returns>the deserialized dictionary</returns>
-        public override IDictionary<string, TValue> FromValue(Value value, object parent)
-            => (value as Map)?.Select(kvp => (kvp.Key, val: BaseConverter.FromValue(kvp.Value, parent)))
-                    ?.ToDictionary(p => p.Key, p => p.val)
+        public override IDictionary<string, TValue?> FromValue(Value? value, object parent)
+            => ((value as Map)?.Select(kvp => (kvp.Key, val: BaseConverter.FromValue(kvp.Value, parent)))
+                    ?.ToDictionary(p => p.Key, p => p.val))
                 ?? throw new ArgumentException("Value not a map", nameof(value));
 
         /// <summary>
@@ -349,8 +350,8 @@ namespace IPA.Config.Stores.Converters
         /// <param name="obj">the dictionary to serialize</param>
         /// <param name="parent">the object that owns the dictionary</param>
         /// <returns>the dictionary serialized as a <see cref="Map"/></returns>
-        public override Value ToValue(IDictionary<string, TValue> obj, object parent)
-            => Value.From(obj.Select(p => new KeyValuePair<string, Value>(p.Key, BaseConverter.ToValue(p.Value, parent))));
+        public override Value? ToValue(IDictionary<string, TValue?>? obj, object parent)
+            => Value.From(obj.Select(p => new KeyValuePair<string, Value?>(p.Key, BaseConverter.ToValue(p.Value, parent))));
     }
 
     /// <summary>
@@ -373,7 +374,7 @@ namespace IPA.Config.Stores.Converters
     /// A converter for instances of <see cref="Dictionary{TKey, TValue}"/>.
     /// </summary>
     /// <typeparam name="TValue">the value type of the dictionary</typeparam>
-    public class DictionaryConverter<TValue> : ValueConverter<Dictionary<string, TValue>>
+    public class DictionaryConverter<TValue> : ValueConverter<Dictionary<string, TValue?>>
     {
         /// <summary>
         /// Gets the converter for the dictionary's value type.
@@ -397,7 +398,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="value">the <see cref="Map"/> to convert</param>
         /// <param name="parent">the parent that will own the resulting object</param>
         /// <returns>the deserialized dictionary</returns>
-        public override Dictionary<string, TValue> FromValue(Value value, object parent)
+        public override Dictionary<string, TValue?> FromValue(Value? value, object parent)
             => (value as Map)?.Select(kvp => (kvp.Key, val: BaseConverter.FromValue(kvp.Value, parent)))
                     ?.ToDictionary(p => p.Key, p => p.val)
                 ?? throw new ArgumentException("Value not a map", nameof(value));
@@ -408,8 +409,8 @@ namespace IPA.Config.Stores.Converters
         /// <param name="obj">the dictionary to serialize</param>
         /// <param name="parent">the object that owns the dictionary</param>
         /// <returns>the dictionary serialized as a <see cref="Map"/></returns>
-        public override Value ToValue(Dictionary<string, TValue> obj, object parent)
-            => Value.From(obj.Select(p => new KeyValuePair<string, Value>(p.Key, BaseConverter.ToValue(p.Value, parent))));
+        public override Value? ToValue(Dictionary<string, TValue?>? obj, object parent)
+            => Value.From(obj?.Select(p => new KeyValuePair<string, Value?>(p.Key, BaseConverter.ToValue(p.Value, parent))));
     }
 
     /// <summary>
@@ -433,7 +434,7 @@ namespace IPA.Config.Stores.Converters
     /// A converter for instances of <see cref="IReadOnlyDictionary{TKey, TValue}"/>.
     /// </summary>
     /// <typeparam name="TValue">the value type of the dictionary</typeparam>
-    public class IReadOnlyDictionaryConverter<TValue> : ValueConverter<IReadOnlyDictionary<string, TValue>>
+    public class IReadOnlyDictionaryConverter<TValue> : ValueConverter<IReadOnlyDictionary<string, TValue?>>
     {
         /// <summary>
         /// Gets the converter for the dictionary's value type.
@@ -457,7 +458,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="value">the <see cref="Map"/> to convert</param>
         /// <param name="parent">the parent that will own the resulting object</param>
         /// <returns>the deserialized dictionary</returns>
-        public override IReadOnlyDictionary<string, TValue> FromValue(Value value, object parent)
+        public override IReadOnlyDictionary<string, TValue?> FromValue(Value? value, object parent)
             => (value as Map)?.Select(kvp => (kvp.Key, val: BaseConverter.FromValue(kvp.Value, parent)))
                     ?.ToDictionary(p => p.Key, p => p.val)
                 ?? throw new ArgumentException("Value not a map", nameof(value));
@@ -468,8 +469,8 @@ namespace IPA.Config.Stores.Converters
         /// <param name="obj">the dictionary to serialize</param>
         /// <param name="parent">the object that owns the dictionary</param>
         /// <returns>the dictionary serialized as a <see cref="Map"/></returns>
-        public override Value ToValue(IReadOnlyDictionary<string, TValue> obj, object parent)
-            => Value.From(obj.Select(p => new KeyValuePair<string, Value>(p.Key, BaseConverter.ToValue(p.Value, parent))));
+        public override Value? ToValue(IReadOnlyDictionary<string, TValue?>? obj, object parent)
+            => Value.From(obj?.Select(p => new KeyValuePair<string, Value?>(p.Key, BaseConverter.ToValue(p.Value, parent))));
     }
 
     /// <summary>
@@ -500,7 +501,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the object which will own the created object</param>
         /// <returns>the deserialized Color object</returns>
         /// <exception cref="ArgumentException">if <paramref name="value"/> is not a <see cref="Text"/> node or couldn't be parsed into a Color object</exception>
-        public override Color FromValue(Value value, object parent)
+        public override Color FromValue(Value? value, object parent)
         {
             if (value is Text t)
             {
@@ -526,146 +527,146 @@ namespace IPA.Config.Stores.Converters
 
     internal class StringConverter : ValueConverter<string>
     {
-        public override string FromValue(Value value, object parent)
+        public override string? FromValue(Value? value, object parent)
             => (value as Text)?.Value;
 
-        public override Value ToValue(string obj, object parent)
+        public override Value? ToValue(string? obj, object parent)
             => Value.From(obj);
     }
 
     internal class CharConverter : ValueConverter<char>
     {
-        public override char FromValue(Value value, object parent)
+        public override char FromValue(Value? value, object parent)
             => (value as Text)?.Value[0]
                 ?? throw new ArgumentException("Value not a text node", nameof(value)); // can throw nullptr
 
-        public override Value ToValue(char obj, object parent)
+        public override Value? ToValue(char obj, object parent)
             => Value.From(char.ToString(obj));
     }
 
     internal class LongConverter : ValueConverter<long>
     {
-        public override long FromValue(Value value, object parent)
+        public override long FromValue(Value? value, object parent)
             => Converter.IntValue(value)
                 ?? throw new ArgumentException("Value not a numeric value", nameof(value));
 
-        public override Value ToValue(long obj, object parent)
+        public override Value? ToValue(long obj, object parent)
             => Value.From(obj);
     }
 
     internal class ULongConverter : ValueConverter<ulong>
     {
-        public override ulong FromValue(Value value, object parent)
+        public override ulong FromValue(Value? value, object parent)
             => (ulong)(Converter.FloatValue(value)
                 ?? throw new ArgumentException("Value not a numeric value", nameof(value)));
 
-        public override Value ToValue(ulong obj, object parent)
+        public override Value? ToValue(ulong obj, object parent)
             => Value.From(obj);
     }
 
     internal class IntPtrConverter : ValueConverter<IntPtr>
     {
-        public override IntPtr FromValue(Value value, object parent)
+        public override IntPtr FromValue(Value? value, object parent)
             => (IntPtr)Converter<long>.Default.FromValue(value, parent);
 
-        public override Value ToValue(IntPtr obj, object parent)
+        public override Value? ToValue(IntPtr obj, object parent)
             => Value.From((long)obj);
     }
 
     internal class UIntPtrConverter : ValueConverter<UIntPtr>
     {
-        public override UIntPtr FromValue(Value value, object parent)
+        public override UIntPtr FromValue(Value? value, object parent)
             => (UIntPtr)Converter<ulong>.Default.FromValue(value, parent);
 
-        public override Value ToValue(UIntPtr obj, object parent)
+        public override Value? ToValue(UIntPtr obj, object parent)
             => Value.From((decimal)obj);
     }
 
     internal class IntConverter : ValueConverter<int>
     {
-        public override int FromValue(Value value, object parent)
+        public override int FromValue(Value? value, object parent)
             => (int)Converter<long>.Default.FromValue(value, parent);
-        public override Value ToValue(int obj, object parent)
+        public override Value? ToValue(int obj, object parent)
             => Value.From(obj);
     }
 
     internal class UIntConverter : ValueConverter<uint>
     {
-        public override uint FromValue(Value value, object parent)
+        public override uint FromValue(Value? value, object parent)
             => (uint)Converter<long>.Default.FromValue(value, parent);
-        public override Value ToValue(uint obj, object parent)
+        public override Value? ToValue(uint obj, object parent)
             => Value.From(obj);
     }
 
     internal class ShortConverter : ValueConverter<short>
     {
-        public override short FromValue(Value value, object parent)
+        public override short FromValue(Value? value, object parent)
             => (short)Converter<long>.Default.FromValue(value, parent);
-        public override Value ToValue(short obj, object parent)
+        public override Value? ToValue(short obj, object parent)
             => Value.From(obj);
     }
 
     internal class UShortConverter : ValueConverter<ushort>
     {
-        public override ushort FromValue(Value value, object parent)
+        public override ushort FromValue(Value? value, object parent)
             => (ushort)Converter<long>.Default.FromValue(value, parent);
-        public override Value ToValue(ushort obj, object parent)
+        public override Value? ToValue(ushort obj, object parent)
             => Value.From(obj);
     }
 
     internal class ByteConverter : ValueConverter<byte>
     {
-        public override byte FromValue(Value value, object parent)
+        public override byte FromValue(Value? value, object parent)
             => (byte)Converter<long>.Default.FromValue(value, parent);
-        public override Value ToValue(byte obj, object parent)
+        public override Value? ToValue(byte obj, object parent)
             => Value.From(obj);
     }
 
     internal class SByteConverter : ValueConverter<sbyte>
     {
-        public override sbyte FromValue(Value value, object parent)
+        public override sbyte FromValue(Value? value, object parent)
             => (sbyte)Converter<long>.Default.FromValue(value, parent);
-        public override Value ToValue(sbyte obj, object parent)
+        public override Value? ToValue(sbyte obj, object parent)
             => Value.From(obj);
     }
 
     internal class DecimalConverter : ValueConverter<decimal>
     {
-        public override decimal FromValue(Value value, object parent)
+        public override decimal FromValue(Value? value, object parent)
             => Converter.FloatValue(value) ?? throw new ArgumentException("Value not a numeric value", nameof(value));
-        public override Value ToValue(decimal obj, object parent)
+        public override Value? ToValue(decimal obj, object parent)
             => Value.From(obj);
     }
 
     internal class FloatConverter : ValueConverter<float>
     {
-        public override float FromValue(Value value, object parent)
+        public override float FromValue(Value? value, object parent)
             => (float)Converter<decimal>.Default.FromValue(value, parent);
-        public override Value ToValue(float obj, object parent)
+        public override Value? ToValue(float obj, object parent)
             => Value.From((decimal)obj);
     }
 
     internal class DoubleConverter : ValueConverter<double>
     {
-        public override double FromValue(Value value, object parent)
+        public override double FromValue(Value? value, object parent)
             => (double)Converter<decimal>.Default.FromValue(value, parent);
-        public override Value ToValue(double obj, object parent)
+        public override Value? ToValue(double obj, object parent)
             => Value.From((decimal)obj);
     }
 
     internal class BooleanConverter : ValueConverter<bool>
     {
-        public override bool FromValue(Value value, object parent)
+        public override bool FromValue(Value? value, object parent)
             => (value as Boolean)?.Value ?? throw new ArgumentException("Value not a Boolean", nameof(value));
-        public override Value ToValue(bool obj, object parent)
+        public override Value? ToValue(bool obj, object parent)
             => Value.From(obj);
     }
 
     internal class DateTimeConverter : ValueConverter<DateTime>
     {
-        public override DateTime FromValue(Value value, object parent)
+        public override DateTime FromValue(Value? value, object parent)
         {
-            if (!(value is Text text))
+            if (value is not Text text)
             {
                 throw new ArgumentException("Value is not of type Text", nameof(value));
             }
@@ -678,14 +679,14 @@ namespace IPA.Config.Stores.Converters
             throw new ArgumentException($"Parsing failed, {text.Value}");
         }
 
-        public override Value ToValue(DateTime obj, object parent) => Value.Text(obj.ToString("O"));
+        public override Value? ToValue(DateTime obj, object parent) => Value.Text(obj.ToString("O"));
     }
 
     internal class DateTimeOffsetConverter : ValueConverter<DateTimeOffset>
     {
-        public override DateTimeOffset FromValue(Value value, object parent)
+        public override DateTimeOffset FromValue(Value? value, object parent)
         {
-            if (!(value is Text text))
+            if (value is not Text text)
             {
                 throw new ArgumentException("Value is not of type Text", nameof(value));
             }
@@ -703,9 +704,9 @@ namespace IPA.Config.Stores.Converters
 
     internal class TimeSpanConverter : ValueConverter<TimeSpan>
     {
-        public override TimeSpan FromValue(Value value, object parent)
+        public override TimeSpan FromValue(Value? value, object parent)
         {
-            if (!(value is Text text))
+            if (value is not Text text)
             {
                 throw new ArgumentException("Value is not of type Text", nameof(value));
             }
@@ -718,6 +719,6 @@ namespace IPA.Config.Stores.Converters
             throw new ArgumentException($"Parsing failed, {text.Value}");
         }
 
-        public override Value ToValue(TimeSpan obj, object parent) => Value.Text(obj.ToString());
+        public override Value? ToValue(TimeSpan obj, object parent) => Value.Text(obj.ToString());
     }
 }

IPA.Loader/Config/Stores/CustomObjectConverter.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using System;
 
 namespace IPA.Config.Stores.Converters
@@ -12,24 +13,26 @@ namespace IPA.Config.Stores.Converters
     {
         private interface IImpl
         {
-            T FromValue(Value value, object parent);
-            Value ToValue(T obj, object parent);
+            T? FromValue(Value? value, object parent);
+            Value? ToValue(T? obj, object parent);
         }
         private class Impl<U> : IImpl where U : class, GeneratedStoreImpl.IGeneratedStore<T>, T
         {
             private static readonly GeneratedStoreImpl.GeneratedStoreCreator creator = GeneratedStoreImpl.GetCreator(typeof(T));
-            private static U Create(GeneratedStoreImpl.IGeneratedStore parent)
-                => creator(parent) as U;
+            private static U Create(GeneratedStoreImpl.IGeneratedStore? parent)
+                => (U)creator(parent);
 
-            public T FromValue(Value value, object parent)
+            public T? FromValue(Value? value, object parent)
             { // lots of casting here, but it works i promise (probably) (parent can be a non-IGeneratedStore, however it won't necessarily behave then)
+                if (value is null) return null;
                 var obj = Create(parent as GeneratedStoreImpl.IGeneratedStore);
                 obj.Deserialize(value);
                 return obj;
             }
 
-            public Value ToValue(T obj, object parent)
+            public Value? ToValue(T? obj, object parent)
             {
+                if (obj is null) return null;
                 if (obj is GeneratedStoreImpl.IGeneratedStore store)
                     return store.Serialize();
                 else
@@ -51,7 +54,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the parent object that will own the deserialized value</param>
         /// <returns>the deserialized value</returns>
         /// <seealso cref="ValueConverter{T}.FromValue(Value, object)"/>
-        public static T Deserialize(Value value, object parent)
+        public static T? Deserialize(Value? value, object parent)
             => impl.FromValue(value, parent);
 
         /// <summary>
@@ -61,7 +64,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the parent object that owns <paramref name="obj"/></param>
         /// <returns>the <see cref="Value"/> tree that represents <paramref name="obj"/></returns>
         /// <seealso cref="ValueConverter{T}.ToValue(T, object)"/>
-        public static Value Serialize(T obj, object parent)
+        public static Value? Serialize(T? obj, object parent)
             => impl.ToValue(obj, parent);
 
         /// <summary>
@@ -71,7 +74,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the parent object that will own the deserialized value</param>
         /// <returns>the deserialized value</returns>
         /// <seealso cref="ValueConverter{T}.FromValue(Value, object)"/>
-        public override T FromValue(Value value, object parent)
+        public override T? FromValue(Value? value, object parent)
             => Deserialize(value, parent);
 
         /// <summary>
@@ -81,7 +84,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the parent object that owns <paramref name="obj"/></param>
         /// <returns>the <see cref="Value"/> tree that represents <paramref name="obj"/></returns>
         /// <seealso cref="ValueConverter{T}.ToValue(T, object)"/>
-        public override Value ToValue(T obj, object parent)
+        public override Value? ToValue(T? obj, object parent)
             => Serialize(obj, parent);
     }
 
@@ -104,7 +107,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the parent object that will own the deserialized value</param>
         /// <returns>the deserialized value</returns>
         /// <seealso cref="ValueConverter{T}.FromValue(Value, object)"/>
-        public static T Deserialize(Value value, object parent)
+        public static T Deserialize(Value? value, object parent)
             => deserialize(value, parent);
 
         /// <summary>
@@ -123,7 +126,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the parent object that will own the deserialized value</param>
         /// <returns>the deserialized value</returns>
         /// <seealso cref="ValueConverter{T}.FromValue(Value, object)"/>
-        public override T FromValue(Value value, object parent)
+        public override T FromValue(Value? value, object parent)
             => Deserialize(value, parent);
 
         /// <summary>
@@ -133,7 +136,7 @@ namespace IPA.Config.Stores.Converters
         /// <param name="parent">the parent object that owns <paramref name="obj"/></param>
         /// <returns>the <see cref="Value"/> tree that represents <paramref name="obj"/></returns>
         /// <seealso cref="ValueConverter{T}.ToValue(T, object)"/>
-        public override Value ToValue(T obj, object parent)
+        public override Value? ToValue(T obj, object parent)
             => Serialize(obj);
     }
 

IPA.Loader/Config/Stores/GeneratedStoreImpl/ConversionDelegates.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -13,12 +14,12 @@ namespace IPA.Config.Stores
     {
 
         internal delegate Value SerializeObject<T>(T obj);
-        internal delegate T DeserializeObject<T>(Value val, object parent);
+        internal delegate T DeserializeObject<T>(Value? val, object parent);
 
         private static class DelegateStore<T> 
         {
-            public static SerializeObject<T> Serialize;
-            public static DeserializeObject<T> Deserialize;
+            public static SerializeObject<T>? Serialize;
+            public static DeserializeObject<T>? Deserialize;
         }
 
         internal static SerializeObject<T> GetSerializerDelegate<T>()

IPA.Loader/Config/Stores/GeneratedStoreImpl/Correction.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using IPA.Config.Stores.Attributes;
 using IPA.Logging;
 using System;

IPA.Loader/Config/Stores/GeneratedStoreImpl/Deserialization.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using IPA.Logging;
 using System;
 using System.Collections;
@@ -43,6 +44,7 @@ namespace IPA.Config.Stores
         private static void EmitDeserializeNullable(ILGenerator il, SerializedMemberInfo member, Type expected, LocalAllocator GetLocal, 
             Action<ILGenerator> thisarg, Action<ILGenerator> parentobj)
         {
+            if (!member.IsNullable) throw new InvalidOperationException("EmitDeserializeNullable called for non-nullable!");
             thisarg ??= il => il.Emit(OpCodes.Ldarg_0);
             parentobj ??= thisarg;
             EmitDeserializeValue(il, member, member.NullableWrappedType, expected, GetLocal, thisarg, parentobj);
@@ -161,6 +163,9 @@ namespace IPA.Config.Stores
         private static void EmitDeserializeConverter(ILGenerator il, SerializedMemberInfo member, Label nextLabel, LocalAllocator GetLocal,
             Action<ILGenerator> thisobj, Action<ILGenerator> parentobj)
         {
+            if (!member.HasConverter)
+                throw new InvalidOperationException("EmitDeserializeConverter called for member without converter");
+
             using var stlocal = GetLocal.Allocate(typeof(Value));
             using var valLocal = GetLocal.Allocate(member.Type);
 

IPA.Loader/Config/Stores/GeneratedStoreImpl/GeneratedStoreImpl.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using IPA.Config.Stores.Attributes;
 using IPA.Logging;
 using System;
@@ -36,13 +37,12 @@ namespace IPA.Config.Stores
         private static readonly MethodInfo CreateGParent = 
             typeof(GeneratedStoreImpl).GetMethod(nameof(Create), BindingFlags.NonPublic | BindingFlags.Static, null, 
                                              CallingConventions.Any, new[] { typeof(IGeneratedStore) }, Array.Empty<ParameterModifier>());
-        internal static T Create<T>(IGeneratedStore parent) where T : class => (T)Create(typeof(T), parent);
+        internal static T Create<T>(IGeneratedStore? parent) where T : class => (T)Create(typeof(T), parent);
 
-        private static IConfigStore Create(Type type, IGeneratedStore parent)
+        private static IConfigStore Create(Type type, IGeneratedStore? parent)
             => GetCreator(type)(parent);
 
-        private static readonly SingleCreationValueCache<Type, (GeneratedStoreCreator ctor, Type type)> generatedCreators
-            = new SingleCreationValueCache<Type, (GeneratedStoreCreator ctor, Type type)>();
+        private static readonly SingleCreationValueCache<Type, (GeneratedStoreCreator ctor, Type type)> generatedCreators = new();
 
         private static (GeneratedStoreCreator ctor, Type type) GetCreatorAndGeneratedType(Type t)
             => generatedCreators.GetOrAdd(t, MakeCreator);
@@ -55,7 +55,7 @@ namespace IPA.Config.Stores
 
         internal const string GeneratedAssemblyName = "IPA.Config.Generated";
 
-        private static AssemblyBuilder assembly = null;
+        private static AssemblyBuilder? assembly;
         private static AssemblyBuilder Assembly
         {
             get
@@ -75,7 +75,7 @@ namespace IPA.Config.Stores
             Assembly.Save(file);
         }
 
-        private static ModuleBuilder module = null;
+        private static ModuleBuilder? module;
         private static ModuleBuilder Module
         {
             get
@@ -88,7 +88,7 @@ namespace IPA.Config.Stores
         }
 
         // TODO: does this need to be a SingleCreationValueCache or similar?
-        private static readonly Dictionary<Type, Dictionary<Type, FieldInfo>> TypeRequiredConverters = new Dictionary<Type, Dictionary<Type, FieldInfo>>();
+        private static readonly Dictionary<Type, Dictionary<Type, FieldInfo>> TypeRequiredConverters = new();
         private static void CreateAndInitializeConvertersFor(Type type, IEnumerable<SerializedMemberInfo> structure)
         {
             if (!TypeRequiredConverters.TryGetValue(type, out var converters))
@@ -96,7 +96,8 @@ namespace IPA.Config.Stores
                 var converterFieldType = Module.DefineType($"{type.FullName}<Converters>",
                     TypeAttributes.Public | TypeAttributes.Sealed | TypeAttributes.Abstract | TypeAttributes.AnsiClass); // a static class
 
-                var uniqueConverterTypes = structure.Where(m => m.HasConverter).Select(m => m.Converter).Distinct().ToArray();
+                var uniqueConverterTypes = structure.Where(m => m.HasConverter)
+                    .Select(m => m.Converter).NonNull().Distinct().ToArray();
                 converters = new Dictionary<Type, FieldInfo>(uniqueConverterTypes.Length);
 
                 foreach (var convType in uniqueConverterTypes)
@@ -122,11 +123,14 @@ namespace IPA.Config.Stores
 
                 TypeRequiredConverters.Add(type, converters);
 
-                converterFieldType.CreateType();
+                _ = converterFieldType.CreateType();
             }
 
-            foreach (var member in structure.Where(m => m.HasConverter))
+            foreach (var member in structure)
+            {
+                if (!member.HasConverter) continue;
                 member.ConverterField = converters[member.Converter];
+            }
         }
     }
 }

IPA.Loader/Config/Stores/GeneratedStoreImpl/IGeneratedStore.cs

@@ -1,4 +1,5 @@
-using IPA.Logging;
+#nullable enable
+using IPA.Logging;
 using System;
 using System.Collections.Generic;
 using System.Reflection;
@@ -42,27 +43,27 @@ namespace IPA.Config.Stores
         internal class Impl : IConfigStore
         {
             private readonly IGeneratedStore generated;
-            private long enteredTransactions = 0;
+            private long enteredTransactions;
 
             internal static ConstructorInfo Ctor = typeof(Impl).GetConstructor(new[] { typeof(IGeneratedStore) });
             public Impl(IGeneratedStore store) => generated = store;
 
-            private readonly AutoResetEvent resetEvent = new AutoResetEvent(false);
+            private readonly AutoResetEvent resetEvent = new(false);
             public WaitHandle SyncObject => resetEvent;
-            public static WaitHandle ImplGetSyncObject(IGeneratedStore s) => FindImpl(s).SyncObject;
+            public static WaitHandle? ImplGetSyncObject(IGeneratedStore s) => FindImpl(s)?.SyncObject;
             internal static MethodInfo ImplGetSyncObjectMethod = typeof(Impl).GetMethod(nameof(ImplGetSyncObject));
 
-            public ReaderWriterLockSlim WriteSyncObject { get; } = new ReaderWriterLockSlim();
-            public static ReaderWriterLockSlim ImplGetWriteSyncObject(IGeneratedStore s) => FindImpl(s)?.WriteSyncObject;
+            public ReaderWriterLockSlim WriteSyncObject { get; } = new();
+            public static ReaderWriterLockSlim? ImplGetWriteSyncObject(IGeneratedStore s) => FindImpl(s)?.WriteSyncObject;
             internal static MethodInfo ImplGetWriteSyncObjectMethod = typeof(Impl).GetMethod(nameof(ImplGetWriteSyncObject));
 
             internal static MethodInfo ImplSignalChangedMethod = typeof(Impl).GetMethod(nameof(ImplSignalChanged));
-            public static void ImplSignalChanged(IGeneratedStore s) => FindImpl(s).SignalChanged();
+            public static void ImplSignalChanged(IGeneratedStore s) => FindImpl(s)?.SignalChanged();
             public void SignalChanged()
             {
                 try
                 {
-                    resetEvent.Set();
+                    _ = resetEvent.Set();
                 }
                 catch (ObjectDisposedException e)
                 {
@@ -72,11 +73,11 @@ namespace IPA.Config.Stores
             }
 
             internal static MethodInfo ImplInvokeChangedMethod = typeof(Impl).GetMethod(nameof(ImplInvokeChanged));
-            public static void ImplInvokeChanged(IGeneratedStore s) => FindImpl(s).InvokeChanged();
+            public static void ImplInvokeChanged(IGeneratedStore s) => FindImpl(s)?.InvokeChanged();
             public void InvokeChanged() => generated.Changed();
 
             internal static MethodInfo ImplTakeReadMethod = typeof(Impl).GetMethod(nameof(ImplTakeRead));
-            public static void ImplTakeRead(IGeneratedStore s) => FindImpl(s).TakeRead();
+            public static void ImplTakeRead(IGeneratedStore s) => FindImpl(s)?.TakeRead();
             public void TakeRead()
             {
                 if (!WriteSyncObject.IsWriteLockHeld)
@@ -84,7 +85,7 @@ namespace IPA.Config.Stores
             }
 
             internal static MethodInfo ImplReleaseReadMethod = typeof(Impl).GetMethod(nameof(ImplReleaseRead));
-            public static void ImplReleaseRead(IGeneratedStore s) => FindImpl(s).ReleaseRead();
+            public static void ImplReleaseRead(IGeneratedStore s) => FindImpl(s)?.ReleaseRead();
             public void ReleaseRead()
             {
                 if (!WriteSyncObject.IsWriteLockHeld)
@@ -92,24 +93,24 @@ namespace IPA.Config.Stores
             }
 
             internal static MethodInfo ImplTakeWriteMethod = typeof(Impl).GetMethod(nameof(ImplTakeWrite));
-            public static void ImplTakeWrite(IGeneratedStore s) => FindImpl(s).TakeWrite();
+            public static void ImplTakeWrite(IGeneratedStore s) => FindImpl(s)?.TakeWrite();
             public void TakeWrite() => WriteSyncObject.EnterWriteLock();
 
             internal static MethodInfo ImplReleaseWriteMethod = typeof(Impl).GetMethod(nameof(ImplReleaseWrite));
-            public static void ImplReleaseWrite(IGeneratedStore s) => FindImpl(s).ReleaseWrite();
+            public static void ImplReleaseWrite(IGeneratedStore s) => FindImpl(s)?.ReleaseWrite();
             public void ReleaseWrite() => WriteSyncObject.ExitWriteLock();
 
             internal static MethodInfo ImplChangeTransactionMethod = typeof(Impl).GetMethod(nameof(ImplChangeTransaction));
-            public static IDisposable ImplChangeTransaction(IGeneratedStore s, IDisposable nest) => FindImpl(s).ChangeTransaction(nest);
+            public static IDisposable? ImplChangeTransaction(IGeneratedStore s, IDisposable nest) => FindImpl(s)?.ChangeTransaction(nest);
             // TODO: improve trasactionals so they don't always save in every case
             public IDisposable ChangeTransaction(IDisposable nest, bool takeWrite = true)
                 => GetFreeTransaction().InitWith(this, nest, takeWrite && !WriteSyncObject.IsWriteLockHeld);
 
-            private ChangeTransactionObj GetFreeTransaction()
+            private static ChangeTransactionObj GetFreeTransaction()
                 => freeTransactionObjs.Count > 0 ? freeTransactionObjs.Pop()
                                                  : new ChangeTransactionObj();
             // TODO: maybe sometimes clean this?
-            private static readonly Stack<ChangeTransactionObj> freeTransactionObjs = new Stack<ChangeTransactionObj>();
+            private static readonly Stack<ChangeTransactionObj> freeTransactionObjs = new();
 
             private sealed class ChangeTransactionObj : IDisposable
             {
@@ -148,7 +149,7 @@ namespace IPA.Config.Stores
                     try
                     {
                         if (data.ownsWrite)
-                            data.impl.ReleaseWrite();
+                            data.impl?.ReleaseWrite();
                     }
                     catch
                     {
@@ -163,14 +164,14 @@ namespace IPA.Config.Stores
                 ~ChangeTransactionObj() => Dispose(false);
             }
 
-            public static Impl FindImpl(IGeneratedStore store)
+            public static Impl? FindImpl(IGeneratedStore store)
             {
                 while (store?.Parent != null) store = store.Parent; // walk to the top of the tree
                 return store?.Impl;
             }
 
             internal static MethodInfo ImplReadFromMethod = typeof(Impl).GetMethod(nameof(ImplReadFrom));
-            public static void ImplReadFrom(IGeneratedStore s, ConfigProvider provider) => FindImpl(s).ReadFrom(provider);
+            public static void ImplReadFrom(IGeneratedStore s, ConfigProvider provider) => FindImpl(s)?.ReadFrom(provider);
             public void ReadFrom(ConfigProvider provider)
             {
                 Logger.config.Debug($"Generated impl ReadFrom {generated.GetType()}");
@@ -183,7 +184,7 @@ namespace IPA.Config.Stores
             }
 
             internal static MethodInfo ImplWriteToMethod = typeof(Impl).GetMethod(nameof(ImplWriteTo));
-            public static void ImplWriteTo(IGeneratedStore s, ConfigProvider provider) => FindImpl(s).WriteTo(provider);
+            public static void ImplWriteTo(IGeneratedStore s, ConfigProvider provider) => FindImpl(s)?.WriteTo(provider);
             public void WriteTo(ConfigProvider provider)
             {
                 Logger.config.Debug($"Generated impl WriteTo {generated.GetType()}");

IPA.Loader/Config/Stores/GeneratedStoreImpl/MakeCreator.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using IPA.Config.Stores.Attributes;
 using IPA.Logging;
 using System;
@@ -21,7 +22,7 @@ namespace IPA.Config.Stores
     internal static partial class GeneratedStoreImpl
     {
 
-        internal delegate IConfigStore GeneratedStoreCreator(IGeneratedStore parent);
+        internal delegate IConfigStore GeneratedStoreCreator(IGeneratedStore? parent);
         private static void GetMethodThis(ILGenerator il) => il.Emit(OpCodes.Ldarg_0);
 
         private static (GeneratedStoreCreator ctor, Type type) MakeCreator(Type type)
@@ -109,7 +110,7 @@ namespace IPA.Config.Stores
             const MethodAttributes virtualMemberMethod = MethodAttributes.Public | MethodAttributes.Virtual | MethodAttributes.HideBySig | MethodAttributes.Final;
 
             #region INotifyPropertyChanged
-            MethodBuilder notifyChanged = null;
+            MethodBuilder? notifyChanged = null;
             if (isINotifyPropertyChanged || hasNotifyAttribute)
             {
                 // we don't actually want to notify if the base class implements it
@@ -639,7 +640,7 @@ namespace IPA.Config.Stores
             #region Members
             foreach (var member in structure.Where(m => m.IsVirtual))
             { // IsVirtual implies !IsField
-                var prop = member.Member as PropertyInfo;
+                var prop = (PropertyInfo)member.Member;
                 var get = prop.GetGetMethod(true);
                 var set = prop.GetSetMethod(true);
 

IPA.Loader/Config/Stores/GeneratedStoreImpl/ObjectStructure.cs

@@ -1,10 +1,12 @@
-using IPA.Config.Stores.Attributes;
+#nullable enable
+using IPA.Config.Stores.Attributes;
 using IPA.Config.Stores.Converters;
 using IPA.Logging;
 using IPA.Utilities;
 using IPA.Utilities.Async;
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reflection;
 using System.Text;
@@ -20,23 +22,25 @@ namespace IPA.Config.Stores
     {
         private class SerializedMemberInfo
         {
-            public string Name;
-            public MemberInfo Member;
-            public Type Type;
+            public string Name = null!;
+            public MemberInfo Member = null!;
+            public Type Type = null!;
             public bool AllowNull;
             public bool IsVirtual;
             public bool IsField;
-            public bool IsNullable; // signifies whether this is a Nullable<T>
+            [MemberNotNullWhen(true, nameof(NullableWrappedType))]
+            public bool IsNullable { get; set; } // signifies whether this is a Nullable<T>
 
-            public bool HasConverter;
-            public bool IsGenericConverter; // used so we can call directly to the generic version if it is
-            public Type Converter;
-            public Type ConverterBase;
-            public Type ConverterTarget;
-            public FieldInfo ConverterField;
+            [MemberNotNullWhen(true, nameof(Converter), nameof(ConverterBase))]
+            public bool HasConverter { get; set; }
+            public bool IsGenericConverter { get; set; } // used so we can call directly to the generic version if it is
+            public Type? Converter;
+            public Type? ConverterBase;
+            public Type? ConverterTarget;
+            public FieldInfo? ConverterField;
 
             // invalid for objects with IsNullable false
-            public Type NullableWrappedType => Nullable.GetUnderlyingType(Type);
+            public Type? NullableWrappedType => Nullable.GetUnderlyingType(Type);
             // invalid for objects with IsNullable false
             public PropertyInfo Nullable_HasValue => Type.GetProperty(nameof(Nullable<int>.HasValue));
             // invalid for objects with IsNullable false
@@ -73,6 +77,8 @@ namespace IPA.Config.Stores
             {
                 if (converterAttr.UseDefaultConverterForType)
                     converterAttr = new UseConverterAttribute(Converter.GetDefaultConverterType(member.Type));
+                if (converterAttr.UseDefaultConverterForType)
+                    throw new InvalidOperationException("How did we get here?"); 
 
                 member.Converter = converterAttr.ConverterType;
                 member.IsGenericConverter = converterAttr.IsGenericConverter;
@@ -100,7 +106,7 @@ namespace IPA.Config.Stores
                 {
                     try
                     {
-                        var conv = Activator.CreateInstance(converterAttr.ConverterType) as IValueConverter;
+                        var conv = (IValueConverter)Activator.CreateInstance(converterAttr.ConverterType);
                         targetType = conv.Type;
                     }
                     catch
@@ -128,8 +134,7 @@ namespace IPA.Config.Stores
             return true;
         }
 
-        private static readonly SingleCreationValueCache<Type, SerializedMemberInfo[]> objectStructureCache 
-            = new SingleCreationValueCache<Type, SerializedMemberInfo[]>();
+        private static readonly SingleCreationValueCache<Type, SerializedMemberInfo[]> objectStructureCache = new();
 
         private static IEnumerable<SerializedMemberInfo> ReadObjectMembers(Type type)
             => objectStructureCache.GetOrAdd(type, t => ReadObjectMembersInternal(type).ToArray());

IPA.Loader/Config/Stores/GeneratedStoreImpl/Serialization.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using IPA.Logging;
 using System;
 using System.Collections.Generic;

IPA.Loader/Config/Stores/GeneratedStorePublicInterface.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Stores.Attributes;
+#nullable enable
+using IPA.Config.Stores.Attributes;
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;

IPA.Loader/Config/Stores/ValueConverter.cs

@@ -1,4 +1,5 @@
-using IPA.Config.Data;
+#nullable enable
+using IPA.Config.Data;
 using System;
 
 namespace IPA.Config.Stores
@@ -31,14 +32,14 @@ namespace IPA.Config.Stores
         /// <param name="obj">the object to convert</param>
         /// <param name="parent">the owning object of <paramref name="obj"/></param>
         /// <returns>a representation of <paramref name="obj"/> as a <see cref="Value"/> structure</returns>
-        Value ToValue(object obj, object parent);
+        Value? ToValue(object? obj, object parent);
         /// <summary>
         /// Converts the given <see cref="Value"/> to the object type handled by this converter.
         /// </summary>
         /// <param name="value">the <see cref="Value"/> to deserialize</param>
         /// <param name="parent">the object that will own the result</param>
         /// <returns>the deserialized object</returns>
-        object FromValue(Value value, object parent);
+        object? FromValue(Value? value, object parent);
         /// <summary>
         /// Gets the type that this <see cref="IValueConverter"/> handles.
         /// </summary>
@@ -59,7 +60,7 @@ namespace IPA.Config.Stores
         /// <param name="parent">the owning object of <paramref name="obj"/></param>
         /// <returns>a representation of <paramref name="obj"/> as a <see cref="Value"/> structure</returns>
         /// <seealso cref="IValueConverter.ToValue"/>
-        public abstract Value ToValue(T obj, object parent);
+        public abstract Value? ToValue(T? obj, object parent);
         /// <summary>
         /// Converts the given <see cref="Value"/> to the object type handled by this converter.
         /// </summary>
@@ -67,10 +68,10 @@ namespace IPA.Config.Stores
         /// <param name="parent">the object that will own the result</param>
         /// <returns>the deserialized object</returns>
         /// <seealso cref="IValueConverter.FromValue"/>
-        public abstract T FromValue(Value value, object parent);
+        public abstract T? FromValue(Value? value, object parent);
 
-        Value IValueConverter.ToValue(object obj, object parent) => ToValue((T)obj, parent);
-        object IValueConverter.FromValue(Value value, object parent) => FromValue(value, parent);
+        Value? IValueConverter.ToValue(object? obj, object parent) => ToValue((T?)obj, parent);
+        object? IValueConverter.FromValue(Value? value, object parent) => FromValue(value, parent);
         Type IValueConverter.Type => typeof(T);
     }
 }

IPA.Loader/Utilities/AlmostVersion.cs

@@ -305,15 +305,19 @@ namespace IPA.Utilities
         /// <param name="value">the <see cref="Text"/> node to convert</param>
         /// <param name="parent">the owner of the new object</param>
         /// <returns></returns>
-        public override AlmostVersion FromValue(Value value, object parent)
-            => new(Converter<string>.Default.FromValue(value, parent));
+        public override AlmostVersion? FromValue(Value? value, object parent)
+            => Converter<string>.Default.FromValue(value, parent) switch
+            {
+                { } v => new(v),
+                _ => null
+            };
         /// <summary>
         /// Converts an <see cref="AlmostVersion"/> to a <see cref="Text"/> node.
         /// </summary>
         /// <param name="obj">the <see cref="AlmostVersion"/> to convert</param>
         /// <param name="parent">the parent of <paramref name="obj"/></param>
         /// <returns>a <see cref="Text"/> node representing <paramref name="obj"/></returns>
-        public override Value ToValue(AlmostVersion obj, object parent)
-            => Value.From(obj.ToString());
+        public override Value? ToValue(AlmostVersion? obj, object parent)
+            => Value.From(obj?.ToString());
     }
 }

IPA/_Attributes.cs

@@ -1,10 +0,0 @@
-#if NET472
-namespace System.Diagnostics.CodeAnalysis
-{
-    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
-    public sealed class DoesNotReturnAttribute : Attribute
-    {
-        public DoesNotReturnAttribute() { }
-    }
-}
-#endif