Merge branch 'develop' into stable

29 files changed, 217 insertions, 200 deletions

diff --git a/src/SMAPI/Framework/ModLoading/AssemblyDefinitionResolver.cs b/src/SMAPI/Framework/ModLoading/AssemblyDefinitionResolver.cs
index 8e2f5ef3..b3378ad1 100644
--- a/src/SMAPI/Framework/ModLoading/AssemblyDefinitionResolver.cs
+++ b/src/SMAPI/Framework/ModLoading/AssemblyDefinitionResolver.cs
@@ -36,6 +36,7 @@ namespace StardewModdingAPI.Framework.ModLoading
 
         /// <summary>Resolve an assembly reference.</summary>
         /// <param name="name">The assembly name.</param>
+        /// <exception cref="AssemblyResolutionException">The assembly can't be resolved.</exception>
         public override AssemblyDefinition Resolve(AssemblyNameReference name)
         {
             return this.ResolveName(name.Name) ?? base.Resolve(name);
@@ -44,6 +45,7 @@ namespace StardewModdingAPI.Framework.ModLoading
         /// <summary>Resolve an assembly reference.</summary>
         /// <param name="name">The assembly name.</param>
         /// <param name="parameters">The assembly reader parameters.</param>
+        /// <exception cref="AssemblyResolutionException">The assembly can't be resolved.</exception>
         public override AssemblyDefinition Resolve(AssemblyNameReference name, ReaderParameters parameters)
         {
             return this.ResolveName(name.Name) ?? base.Resolve(name, parameters);
@@ -55,9 +57,9 @@ namespace StardewModdingAPI.Framework.ModLoading
         *********/
         /// <summary>Resolve a known assembly definition based on its short or full name.</summary>
         /// <param name="name">The assembly's short or full name.</param>
-        private AssemblyDefinition ResolveName(string name)
+        private AssemblyDefinition? ResolveName(string name)
         {
-            return this.Lookup.TryGetValue(name, out AssemblyDefinition match)
+            return this.Lookup.TryGetValue(name, out AssemblyDefinition? match)
                 ? match
                 : null;
         }
diff --git a/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs b/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs
index cb5fa2ae..72b547b1 100644
--- a/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs
+++ b/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs
@@ -36,13 +36,13 @@ namespace StardewModdingAPI.Framework.ModLoading
         private readonly AssemblyDefinitionResolver AssemblyDefinitionResolver;
 
         /// <summary>Provides assembly symbol readers for Mono.Cecil.</summary>
-        private readonly SymbolReaderProvider SymbolReaderProvider = new SymbolReaderProvider();
+        private readonly SymbolReaderProvider SymbolReaderProvider = new();
 
         /// <summary>Provides assembly symbol writers for Mono.Cecil.</summary>
-        private readonly SymbolWriterProvider SymbolWriterProvider = new SymbolWriterProvider();
+        private readonly SymbolWriterProvider SymbolWriterProvider = new();
 
         /// <summary>The objects to dispose as part of this instance.</summary>
-        private readonly HashSet<IDisposable> Disposables = new HashSet<IDisposable>();
+        private readonly HashSet<IDisposable> Disposables = new();
 
         /// <summary>Whether to rewrite mods for compatibility.</summary>
         private readonly bool RewriteMods;
@@ -94,7 +94,12 @@ namespace StardewModdingAPI.Framework.ModLoading
             // get referenced local assemblies
             AssemblyParseResult[] assemblies;
             {
-                HashSet<string> visitedAssemblyNames = new HashSet<string>(AppDomain.CurrentDomain.GetAssemblies().Select(p => p.GetName().Name)); // don't try loading assemblies that are already loaded
+                HashSet<string> visitedAssemblyNames = new HashSet<string>( // don't try loading assemblies that are already loaded
+                    from assembly in AppDomain.CurrentDomain.GetAssemblies()
+                    let name = assembly.GetName().Name
+                    where name != null
+                    select name
+                );
                 assemblies = this.GetReferencedLocalAssemblies(new FileInfo(assemblyPath), visitedAssemblyNames, this.AssemblyDefinitionResolver).ToArray();
             }
 
@@ -111,11 +116,11 @@ namespace StardewModdingAPI.Framework.ModLoading
 
             // rewrite & load assemblies in leaf-to-root order
             bool oneAssembly = assemblies.Length == 1;
-            Assembly lastAssembly = null;
+            Assembly? lastAssembly = null;
             HashSet<string> loggedMessages = new HashSet<string>();
             foreach (AssemblyParseResult assembly in assemblies)
             {
-                if (assembly.Status == AssemblyLoadStatus.AlreadyLoaded)
+                if (!assembly.HasDefinition)
                     continue;
 
                 // rewrite assembly
@@ -138,11 +143,11 @@ namespace StardewModdingAPI.Framework.ModLoading
                 if (changed)
                 {
                     if (!oneAssembly)
-                        this.Monitor.Log($"      Loading {assembly.File.Name} (rewritten)...", LogLevel.Trace);
+                        this.Monitor.Log($"      Loading {assembly.File.Name} (rewritten)...");
 
                     // load assembly
-                    using MemoryStream outAssemblyStream = new MemoryStream();
-                    using MemoryStream outSymbolStream = new MemoryStream();
+                    using MemoryStream outAssemblyStream = new();
+                    using MemoryStream outSymbolStream = new();
                     assembly.Definition.Write(outAssemblyStream, new WriterParameters { WriteSymbols = true, SymbolStream = outSymbolStream, SymbolWriterProvider = this.SymbolWriterProvider });
                     byte[] bytes = outAssemblyStream.ToArray();
                     lastAssembly = Assembly.Load(bytes, outSymbolStream.ToArray());
@@ -150,7 +155,7 @@ namespace StardewModdingAPI.Framework.ModLoading
                 else
                 {
                     if (!oneAssembly)
-                        this.Monitor.Log($"      Loading {assembly.File.Name}...", LogLevel.Trace);
+                        this.Monitor.Log($"      Loading {assembly.File.Name}...");
                     lastAssembly = Assembly.UnsafeLoadFrom(assembly.File.FullName);
                 }
 
@@ -163,7 +168,7 @@ namespace StardewModdingAPI.Framework.ModLoading
                 throw new IncompatibleInstructionException();
 
             // last assembly loaded is the root
-            return lastAssembly;
+            return lastAssembly!;
         }
 
         /// <summary>Get whether an assembly is loaded.</summary>
@@ -172,7 +177,8 @@ namespace StardewModdingAPI.Framework.ModLoading
         {
             try
             {
-                return this.AssemblyDefinitionResolver.Resolve(reference) != null;
+                _ = this.AssemblyDefinitionResolver.Resolve(reference);
+                return true;
             }
             catch (AssemblyResolutionException)
             {
@@ -188,7 +194,7 @@ namespace StardewModdingAPI.Framework.ModLoading
         /// assemblies (especially with Mono). Since this is meant to be called on <see cref="AppDomain.AssemblyResolve"/>,
         /// the implicit assumption is that loading the exact assembly failed.
         /// </remarks>
-        public static Assembly ResolveAssembly(string name)
+        public static Assembly? ResolveAssembly(string name)
         {
             string shortName = name.Split(new[] { ',' }, 2).First(); // get simple name (without version and culture)
             return AppDomain.CurrentDomain
@@ -210,7 +216,8 @@ namespace StardewModdingAPI.Framework.ModLoading
         /// <summary>Track an object for disposal as part of the assembly loader.</summary>
         /// <typeparam name="T">The instance type.</typeparam>
         /// <param name="instance">The disposable instance.</param>
-        private T TrackForDisposal<T>(T instance) where T : IDisposable
+        private T TrackForDisposal<T>(T instance)
+            where T : IDisposable
         {
             this.Disposables.Add(instance);
             return instance;
@@ -241,7 +248,7 @@ namespace StardewModdingAPI.Framework.ModLoading
                 try
                 {
                     // read assembly with symbols
-                    FileInfo symbolsFile = new FileInfo(Path.Combine(Path.GetDirectoryName(file.FullName)!, Path.GetFileNameWithoutExtension(file.FullName)) + ".pdb");
+                    FileInfo symbolsFile = new(Path.Combine(Path.GetDirectoryName(file.FullName)!, Path.GetFileNameWithoutExtension(file.FullName)) + ".pdb");
                     if (symbolsFile.Exists)
                         this.SymbolReaderProvider.TryAddSymbolData(file.Name, () => this.TrackForDisposal(symbolsFile.OpenRead()));
                     assembly = this.TrackForDisposal(AssemblyDefinition.ReadAssembly(readStream, new ReaderParameters(ReadingMode.Immediate) { AssemblyResolver = assemblyResolver, InMemory = true, ReadSymbols = true, SymbolReaderProvider = this.SymbolReaderProvider }));
@@ -266,7 +273,7 @@ namespace StardewModdingAPI.Framework.ModLoading
             // yield referenced assemblies
             foreach (AssemblyNameReference dependency in assembly.MainModule.AssemblyReferences)
             {
-                FileInfo dependencyFile = new FileInfo(Path.Combine(file.Directory.FullName, $"{dependency.Name}.dll"));
+                FileInfo dependencyFile = new(Path.Combine(file.Directory.FullName, $"{dependency.Name}.dll"));
                 foreach (AssemblyParseResult result in this.GetReferencedLocalAssemblies(dependencyFile, visitedAssemblyNames, assemblyResolver))
                     yield return result;
             }
@@ -319,9 +326,9 @@ namespace StardewModdingAPI.Framework.ModLoading
                     // rewrite types using custom attributes
                     foreach (TypeDefinition type in module.GetTypes())
                     {
-                        foreach (var attr in type.CustomAttributes)
+                        foreach (CustomAttribute attr in type.CustomAttributes)
                         {
-                            foreach (var conField in attr.ConstructorArguments)
+                            foreach (CustomAttributeArgument conField in attr.ConstructorArguments)
                             {
                                 if (conField.Value is TypeReference typeRef)
                                     this.ChangeTypeScope(typeRef);
@@ -333,7 +340,7 @@ namespace StardewModdingAPI.Framework.ModLoading
 
             // find or rewrite code
             IInstructionHandler[] handlers = new InstructionMetadata().GetHandlers(this.ParanoidMode, platformChanged, this.RewriteMods).ToArray();
-            RecursiveRewriter rewriter = new RecursiveRewriter(
+            RecursiveRewriter rewriter = new(
                 module: module,
                 rewriteModule: curModule =>
                 {
@@ -380,7 +387,7 @@ namespace StardewModdingAPI.Framework.ModLoading
         {
             // get message template
             // ($phrase is replaced with the noun phrase or messages)
-            string template = null;
+            string? template = null;
             switch (result)
             {
                 case InstructionHandleResult.Rewritten:
@@ -439,20 +446,20 @@ namespace StardewModdingAPI.Framework.ModLoading
             // format messages
             string phrase = handler.Phrases.Any()
                 ? string.Join(", ", handler.Phrases)
-                : handler.DefaultPhrase ?? handler.GetType().Name;
+                : handler.DefaultPhrase;
             this.Monitor.LogOnce(loggedMessages, template.Replace("$phrase", phrase));
         }
 
         /// <summary>Get the correct reference to use for compatibility with the current platform.</summary>
         /// <param name="type">The type reference to rewrite.</param>
-        private void ChangeTypeScope(TypeReference type)
+        private void ChangeTypeScope(TypeReference? type)
         {
             // check skip conditions
             if (type == null || type.FullName.StartsWith("System."))
                 return;
 
             // get assembly
-            if (!this.TypeAssemblies.TryGetValue(type.FullName, out Assembly assembly))
+            if (!this.TypeAssemblies.TryGetValue(type.FullName, out Assembly? assembly))
                 return;
 
             // replace scope
diff --git a/src/SMAPI/Framework/ModLoading/AssemblyParseResult.cs b/src/SMAPI/Framework/ModLoading/AssemblyParseResult.cs
index b56a776c..b133f8d6 100644
--- a/src/SMAPI/Framework/ModLoading/AssemblyParseResult.cs
+++ b/src/SMAPI/Framework/ModLoading/AssemblyParseResult.cs
@@ -1,3 +1,5 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using Mono.Cecil;
 
@@ -13,11 +15,15 @@ namespace StardewModdingAPI.Framework.ModLoading
         public readonly FileInfo File;
 
         /// <summary>The assembly definition.</summary>
-        public readonly AssemblyDefinition Definition;
+        public readonly AssemblyDefinition? Definition;
 
         /// <summary>The result of the assembly load.</summary>
         public AssemblyLoadStatus Status;
 
+        /// <summary>Whether the <see cref="Definition"/> is loaded and ready (i.e. the <see cref="Status"/> is not <see cref="AssemblyLoadStatus.AlreadyLoaded"/> or <see cref="AssemblyLoadStatus.Failed"/>).</summary>
+        [MemberNotNullWhen(true, nameof(AssemblyParseResult.Definition))]
+        public bool HasDefinition => this.Status == AssemblyLoadStatus.Okay;
+
 
         /*********
         ** Public methods
@@ -26,11 +32,14 @@ namespace StardewModdingAPI.Framework.ModLoading
         /// <param name="file">The original assembly file.</param>
         /// <param name="assembly">The assembly definition.</param>
         /// <param name="status">The result of the assembly load.</param>
-        public AssemblyParseResult(FileInfo file, AssemblyDefinition assembly, AssemblyLoadStatus status)
+        public AssemblyParseResult(FileInfo file, AssemblyDefinition? assembly, AssemblyLoadStatus status)
         {
             this.File = file;
             this.Definition = assembly;
             this.Status = status;
+
+            if (status == AssemblyLoadStatus.Okay && assembly == null)
+                throw new InvalidOperationException($"Invalid assembly parse result: load status {status} with a null assembly.");
         }
     }
 }
diff --git a/src/SMAPI/Framework/ModLoading/Finders/EventFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/EventFinder.cs
index 124951a5..f5d449c5 100644
--- a/src/SMAPI/Framework/ModLoading/Finders/EventFinder.cs
+++ b/src/SMAPI/Framework/ModLoading/Finders/EventFinder.cs
@@ -55,7 +55,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         {
             if (this.MethodNames.Any())
             {
-                MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+                MethodReference? methodRef = RewriteHelper.AsMethodReference(instruction);
                 if (methodRef != null && methodRef.DeclaringType.FullName == this.FullTypeName && this.MethodNames.Contains(methodRef.Name))
                 {
                     string eventName = methodRef.Name.Split(new[] { '_' }, 2)[1];
diff --git a/src/SMAPI/Framework/ModLoading/Finders/FieldFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/FieldFinder.cs
index 68415123..7fe4abec 100644
--- a/src/SMAPI/Framework/ModLoading/Finders/FieldFinder.cs
+++ b/src/SMAPI/Framework/ModLoading/Finders/FieldFinder.cs
@@ -49,7 +49,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         {
             if (this.FieldNames.Any())
             {
-                FieldReference fieldRef = RewriteHelper.AsFieldReference(instruction);
+                FieldReference? fieldRef = RewriteHelper.AsFieldReference(instruction);
                 if (fieldRef != null && fieldRef.DeclaringType.FullName == this.FullTypeName && this.FieldNames.Contains(fieldRef.Name))
                 {
                     this.FieldNames.Remove(fieldRef.Name);
diff --git a/src/SMAPI/Framework/ModLoading/Finders/MethodFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/MethodFinder.cs
index d2340f01..e8fdc8c7 100644
--- a/src/SMAPI/Framework/ModLoading/Finders/MethodFinder.cs
+++ b/src/SMAPI/Framework/ModLoading/Finders/MethodFinder.cs
@@ -52,7 +52,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         /// <param name="instruction">The IL instruction.</param>
         protected bool IsMatch(Instruction instruction)
         {
-            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            MethodReference? methodRef = RewriteHelper.AsMethodReference(instruction);
             return
                 methodRef != null
                 && methodRef.DeclaringType.FullName == this.FullTypeName
diff --git a/src/SMAPI/Framework/ModLoading/Finders/PropertyFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/PropertyFinder.cs
index 99344848..2af76f55 100644
--- a/src/SMAPI/Framework/ModLoading/Finders/PropertyFinder.cs
+++ b/src/SMAPI/Framework/ModLoading/Finders/PropertyFinder.cs
@@ -52,7 +52,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         /// <param name="instruction">The IL instruction.</param>
         protected bool IsMatch(Instruction instruction)
         {
-            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            MethodReference? methodRef = RewriteHelper.AsMethodReference(instruction);
             return
                 methodRef != null
                 && methodRef.DeclaringType.FullName == this.FullTypeName
diff --git a/src/SMAPI/Framework/ModLoading/Finders/ReferenceToMemberWithUnexpectedTypeFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/ReferenceToMemberWithUnexpectedTypeFinder.cs
index 8c1cae2b..f34542c3 100644
--- a/src/SMAPI/Framework/ModLoading/Finders/ReferenceToMemberWithUnexpectedTypeFinder.cs
+++ b/src/SMAPI/Framework/ModLoading/Finders/ReferenceToMemberWithUnexpectedTypeFinder.cs
@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
@@ -32,11 +33,11 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         public override bool Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction)
         {
             // field reference
-            FieldReference fieldRef = RewriteHelper.AsFieldReference(instruction);
+            FieldReference? fieldRef = RewriteHelper.AsFieldReference(instruction);
             if (fieldRef != null && this.ShouldValidate(fieldRef.DeclaringType))
             {
                 // get target field
-                FieldDefinition targetField = fieldRef.DeclaringType.Resolve()?.Fields.FirstOrDefault(p => p.Name == fieldRef.Name);
+                FieldDefinition? targetField = fieldRef.DeclaringType.Resolve()?.Fields.FirstOrDefault(p => p.Name == fieldRef.Name);
                 if (targetField == null)
                     return false;
 
@@ -49,16 +50,16 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
             }
 
             // method reference
-            MethodReference methodReference = RewriteHelper.AsMethodReference(instruction);
+            MethodReference? methodReference = RewriteHelper.AsMethodReference(instruction);
             if (methodReference != null && !this.IsUnsupported(methodReference) && this.ShouldValidate(methodReference.DeclaringType))
             {
                 // get potential targets
-                MethodDefinition[] candidateMethods = methodReference.DeclaringType.Resolve()?.Methods.Where(found => found.Name == methodReference.Name).ToArray();
+                MethodDefinition[]? candidateMethods = methodReference.DeclaringType.Resolve()?.Methods.Where(found => found.Name == methodReference.Name).ToArray();
                 if (candidateMethods == null || !candidateMethods.Any())
                     return false;
 
                 // compare return types
-                MethodDefinition methodDef = methodReference.Resolve();
+                MethodDefinition? methodDef = methodReference.Resolve();
                 if (methodDef == null)
                     return false; // validated by ReferenceToMissingMemberFinder
 
@@ -78,7 +79,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         *********/
         /// <summary>Whether references to the given type should be validated.</summary>
         /// <param name="type">The type reference.</param>
-        private bool ShouldValidate(TypeReference type)
+        private bool ShouldValidate([NotNullWhen(true)] TypeReference? type)
         {
             return type != null && this.ValidateReferencesToAssemblies.Contains(type.Scope.Name);
         }
diff --git a/src/SMAPI/Framework/ModLoading/Finders/ReferenceToMissingMemberFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/ReferenceToMissingMemberFinder.cs
index d305daf4..fae7fb12 100644
--- a/src/SMAPI/Framework/ModLoading/Finders/ReferenceToMissingMemberFinder.cs
+++ b/src/SMAPI/Framework/ModLoading/Finders/ReferenceToMissingMemberFinder.cs
@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
 using StardewModdingAPI.Framework.ModLoading.Framework;
@@ -31,10 +32,10 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         public override bool Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction)
         {
             // field reference
-            FieldReference fieldRef = RewriteHelper.AsFieldReference(instruction);
+            FieldReference? fieldRef = RewriteHelper.AsFieldReference(instruction);
             if (fieldRef != null && this.ShouldValidate(fieldRef.DeclaringType))
             {
-                FieldDefinition target = fieldRef.Resolve();
+                FieldDefinition? target = fieldRef.Resolve();
                 if (target == null || target.HasConstant)
                 {
                     this.MarkFlag(InstructionHandleResult.NotCompatible, $"reference to {fieldRef.DeclaringType.FullName}.{fieldRef.Name} (no such field)");
@@ -43,10 +44,10 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
             }
 
             // method reference
-            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            MethodReference? methodRef = RewriteHelper.AsMethodReference(instruction);
             if (methodRef != null && this.ShouldValidate(methodRef.DeclaringType) && !this.IsUnsupported(methodRef))
             {
-                MethodDefinition target = methodRef.Resolve();
+                MethodDefinition? target = methodRef.Resolve();
                 if (target == null)
                 {
                     string phrase;
@@ -71,7 +72,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         *********/
         /// <summary>Whether references to the given type should be validated.</summary>
         /// <param name="type">The type reference.</param>
-        private bool ShouldValidate(TypeReference type)
+        private bool ShouldValidate([NotNullWhen(true)] TypeReference? type)
         {
             return type != null && this.ValidateReferencesToAssemblies.Contains(type.Scope.Name);
         }
diff --git a/src/SMAPI/Framework/ModLoading/Finders/TypeAssemblyFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/TypeAssemblyFinder.cs
index 24ab2eca..17acbf9a 100644
--- a/src/SMAPI/Framework/ModLoading/Finders/TypeAssemblyFinder.cs
+++ b/src/SMAPI/Framework/ModLoading/Finders/TypeAssemblyFinder.cs
@@ -17,7 +17,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         private readonly InstructionHandleResult Result;
 
         /// <summary>Get whether a matched type should be ignored.</summary>
-        private readonly Func<TypeReference, bool> ShouldIgnore;
+        private readonly Func<TypeReference, bool>? ShouldIgnore;
 
 
         /*********
@@ -27,7 +27,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         /// <param name="assemblyName">The full assembly name to which to find references.</param>
         /// <param name="result">The result to return for matching instructions.</param>
         /// <param name="shouldIgnore">Get whether a matched type should be ignored.</param>
-        public TypeAssemblyFinder(string assemblyName, InstructionHandleResult result, Func<TypeReference, bool> shouldIgnore = null)
+        public TypeAssemblyFinder(string assemblyName, InstructionHandleResult result, Func<TypeReference, bool>? shouldIgnore = null)
             : base(defaultPhrase: $"{assemblyName} assembly")
         {
             this.AssemblyName = assemblyName;
diff --git a/src/SMAPI/Framework/ModLoading/Finders/TypeFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/TypeFinder.cs
index 260a8df8..77762f41 100644
--- a/src/SMAPI/Framework/ModLoading/Finders/TypeFinder.cs
+++ b/src/SMAPI/Framework/ModLoading/Finders/TypeFinder.cs
@@ -18,7 +18,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         private readonly InstructionHandleResult Result;
 
         /// <summary>Get whether a matched type should be ignored.</summary>
-        private readonly Func<TypeReference, bool> ShouldIgnore;
+        private readonly Func<TypeReference, bool>? ShouldIgnore;
 
 
         /*********
@@ -28,7 +28,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         /// <param name="fullTypeNames">The full type names to match.</param>
         /// <param name="result">The result to return for matching instructions.</param>
         /// <param name="shouldIgnore">Get whether a matched type should be ignored.</param>
-        public TypeFinder(string[] fullTypeNames, InstructionHandleResult result, Func<TypeReference, bool> shouldIgnore = null)
+        public TypeFinder(string[] fullTypeNames, InstructionHandleResult result, Func<TypeReference, bool>? shouldIgnore = null)
             : base(defaultPhrase: $"{string.Join(", ", fullTypeNames)} type{(fullTypeNames.Length != 1 ? "s" : "")}") // default phrase should never be used
         {
             this.FullTypeNames = new HashSet<string>(fullTypeNames);
@@ -40,7 +40,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Finders
         /// <param name="fullTypeName">The full type name to match.</param>
         /// <param name="result">The result to return for matching instructions.</param>
         /// <param name="shouldIgnore">Get whether a matched type should be ignored.</param>
-        public TypeFinder(string fullTypeName, InstructionHandleResult result, Func<TypeReference, bool> shouldIgnore = null)
+        public TypeFinder(string fullTypeName, InstructionHandleResult result, Func<TypeReference, bool>? shouldIgnore = null)
             : this(new[] { fullTypeName }, result, shouldIgnore) { }
 
         /// <inheritdoc />
diff --git a/src/SMAPI/Framework/ModLoading/Framework/BaseInstructionHandler.cs b/src/SMAPI/Framework/ModLoading/Framework/BaseInstructionHandler.cs
index d5d1b38e..865bf076 100644
--- a/src/SMAPI/Framework/ModLoading/Framework/BaseInstructionHandler.cs
+++ b/src/SMAPI/Framework/ModLoading/Framework/BaseInstructionHandler.cs
@@ -57,7 +57,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Framework
         /// <param name="flag">The result flag to set.</param>
         /// <param name="resultMessage">The result message to add.</param>
         /// <returns>Returns true for convenience.</returns>
-        protected bool MarkFlag(InstructionHandleResult flag, string resultMessage = null)
+        protected bool MarkFlag(InstructionHandleResult flag, string? resultMessage = null)
         {
             this.Flags.Add(flag);
             if (resultMessage != null)
diff --git a/src/SMAPI/Framework/ModLoading/Framework/RecursiveRewriter.cs b/src/SMAPI/Framework/ModLoading/Framework/RecursiveRewriter.cs
index 4f14a579..55369602 100644
--- a/src/SMAPI/Framework/ModLoading/Framework/RecursiveRewriter.cs
+++ b/src/SMAPI/Framework/ModLoading/Framework/RecursiveRewriter.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
@@ -8,6 +9,7 @@ using Mono.Collections.Generic;
 namespace StardewModdingAPI.Framework.ModLoading.Framework
 {
     /// <summary>Handles recursively rewriting loaded assembly code.</summary>
+    [SuppressMessage("ReSharper", "AccessToModifiedClosure", Justification = "Rewrite callbacks are invoked immediately.")]
     internal class RecursiveRewriter
     {
         /*********
@@ -75,7 +77,7 @@ namespace StardewModdingAPI.Framework.ModLoading.Framework
             {
                 changed |= this.RewriteModuleImpl(this.Module);
 
-                foreach (var type in types)
+                foreach (TypeDefinition type in types)
                     changed |= this.RewriteTypeDefinition(type);
             }
             catch (Exception ex)