Improve corlib type resolution during unstripping

Il2CppInterop.Generator/Contexts/RewriteGlobalContext.cs

@@ -13,6 +13,7 @@ public class RewriteGlobalContext : IDisposable
 
     private readonly Dictionary<string, AssemblyRewriteContext> myAssemblies = new();
     private readonly Dictionary<AssemblyDefinition, AssemblyRewriteContext> myAssembliesByOld = new();
+    private readonly Dictionary<AssemblyDefinition, AssemblyRewriteContext> myAssembliesByNew = new();
     internal readonly Dictionary<TypeDefinition, string> PreviousRenamedTypes = new();
     internal readonly Dictionary<TypeDefinition, string> RenamedTypes = new();
 
@@ -65,6 +66,7 @@ internal void AddAssemblyContext(string assemblyName, AssemblyRewriteContext con
         myAssemblies[assemblyName] = context;
         if (context.OriginalAssembly != null)
             myAssembliesByOld[context.OriginalAssembly] = context;
+        myAssembliesByNew[context.NewAssembly] = context;
     }
 
     public AssemblyRewriteContext GetNewAssemblyForOriginal(AssemblyDefinition oldAssembly)
@@ -120,9 +122,14 @@ public AssemblyRewriteContext GetAssemblyByName(string name)
         return null;
     }
 
+    public AssemblyRewriteContext GetContextForNewAssembly(AssemblyDefinition assembly)
+    {
+        return myAssembliesByNew[assembly];
+    }
+
     public TypeRewriteContext GetContextForNewType(TypeDefinition type)
     {
-        return GetAssemblyByName(type.Module!.Assembly!.Name!).GetContextForNewType(type);
+        return GetContextForNewAssembly(type.Module!.Assembly!).GetContextForNewType(type);
     }
 
     public MethodDefinition? CreateParamsMethod(MethodDefinition originalMethod, MethodDefinition newMethod,

Il2CppInterop.Generator/Extensions/AsmResolverExtensions.cs

@@ -7,10 +7,20 @@ namespace Il2CppInterop.Generator.Extensions;
 
 internal static class AsmResolverExtensions
 {
+    /// <summary>
+    /// Boolean, Char, or numeric type
+    /// </summary>
     public static bool IsPrimitive(this TypeSignature type)
     {
-        //https://github.com/jbevain/cecil/blob/8e1ae7b4ea67ccc38cb8db3ded6802643109ffd7/Mono.Cecil/TypeReference.cs#L286
-        return type is CorLibTypeSignature { ElementType: >= ElementType.Boolean and <= ElementType.R8 or ElementType.I or ElementType.U };
+        return (type as CorLibTypeSignature)?.ElementType.IsPrimitive() ?? false;
+    }
+
+    /// <summary>
+    /// Boolean, Char, or numeric type
+    /// </summary>
+    public static bool IsPrimitive(this ElementType elementType)
+    {
+        return elementType is >= ElementType.Boolean and <= ElementType.R8 or ElementType.I or ElementType.U;
     }
 
     public static TypeSignature GetElementType(this TypeSignature type) => type switch

Il2CppInterop.Generator/Passes/Pass80UnstripMethods.cs

@@ -172,14 +172,14 @@ private static PropertyDefinition GetOrCreateProperty(MethodDefinition unityMeth
     }
 
     internal static TypeSignature? ResolveTypeInNewAssemblies(RewriteGlobalContext context, TypeSignature? unityType,
-        RuntimeAssemblyReferences imports)
+        RuntimeAssemblyReferences imports, bool useSystemCorlibPrimitives = true)
     {
-        var resolved = ResolveTypeInNewAssembliesRaw(context, unityType, imports);
+        var resolved = ResolveTypeInNewAssembliesRaw(context, unityType, imports, useSystemCorlibPrimitives);
         return resolved != null ? imports.Module.DefaultImporter.ImportTypeSignature(resolved) : null;
     }
 
     internal static TypeSignature? ResolveTypeInNewAssembliesRaw(RewriteGlobalContext context, TypeSignature? unityType,
-        RuntimeAssemblyReferences imports)
+        RuntimeAssemblyReferences imports, bool useSystemCorlibPrimitives = true)
     {
         if (unityType is null)
             return null;
@@ -264,10 +264,9 @@ private static PropertyDefinition GetOrCreateProperty(MethodDefinition unityMeth
         var targetAssemblyName = unityType.Scope!.Name!;
         if (targetAssemblyName.EndsWith(".dll"))
             targetAssemblyName = targetAssemblyName.Substring(0, targetAssemblyName.Length - 4);
-        if ((targetAssemblyName == "mscorlib" || targetAssemblyName == "netstandard") &&
-            (unityType.IsValueType || unityType.FullName == "System.String" ||
-             unityType.FullName == "System.Void") && unityType.FullName != "System.RuntimeTypeHandle")
-            return imports.Module.ImportCorlibReference(unityType.FullName);
+
+        if (useSystemCorlibPrimitives && (unityType.IsPrimitive() || unityType.ElementType is ElementType.String or ElementType.Void))
+            return imports.Module.CorLibTypeFactory.FromElementType(unityType.ElementType);
 
         if (targetAssemblyName == "UnityEngine")
             foreach (var assemblyRewriteContext in context.Assemblies)

Il2CppInterop.Generator/Utils/UnstripTranslator.cs

@@ -103,9 +103,13 @@ public static bool TranslateMethod(MethodDefinition original, MethodDefinition t
             }
             else if (bodyInstruction.OpCode.OperandType == CilOperandType.InlineField)
             {
+                // This code doesn't handle fields in the corlib types well.
+                // Static fields are fine, but references to instance fields can't be redirected.
+
                 var fieldArg = (IFieldDescriptor)bodyInstruction.Operand;
+                var useSystemCorlibType = fieldArg.Signature?.HasThis ?? true;
                 var fieldDeclarer =
-                    Pass80UnstripMethods.ResolveTypeInNewAssembliesRaw(globalContext, fieldArg.DeclaringType!.ToTypeSignature(), imports);
+                    Pass80UnstripMethods.ResolveTypeInNewAssembliesRaw(globalContext, fieldArg.DeclaringType!.ToTypeSignature(), imports, useSystemCorlibType);
                 if (fieldDeclarer == null)
                     return false;
                 var fieldDeclarerDefinition = fieldDeclarer.Resolve();
@@ -157,9 +161,13 @@ public static bool TranslateMethod(MethodDefinition original, MethodDefinition t
             }
             else if (bodyInstruction.OpCode.OperandType == CilOperandType.InlineMethod)
             {
+                // This code doesn't handle methods in the corlib types well.
+                // Static methods are fine, but references to instance methods can't be redirected.
+
                 var methodArg = (IMethodDescriptor)bodyInstruction.Operand;
+                var useSystemCorlibType = methodArg.Signature?.HasThis ?? true;
                 var methodDeclarer =
-                    Pass80UnstripMethods.ResolveTypeInNewAssemblies(globalContext, methodArg.DeclaringType?.ToTypeSignature(), imports);
+                    Pass80UnstripMethods.ResolveTypeInNewAssemblies(globalContext, methodArg.DeclaringType?.ToTypeSignature(), imports, useSystemCorlibType);
                 if (methodDeclarer == null)
                     return false;