From 0f2cd5aa8e734e48a209e1691d34db3d3d1e9a41 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Sim=C3=B5es?= <jose.simoes@eclo.solutions>
Date: Thu, 3 Jul 2025 17:51:43 +0100
Subject: [PATCH] Fix ResolveToken for TypeSpec with MVAR

- Now checking if caller or caller generic type is null.
---
 src/CLR/Core/TypeSystem.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/CLR/Core/TypeSystem.cpp b/src/CLR/Core/TypeSystem.cpp
index 3a0253c9b0..2dde482801 100644
--- a/src/CLR/Core/TypeSystem.cpp
+++ b/src/CLR/Core/TypeSystem.cpp
@@ -1046,6 +1046,13 @@ bool CLR_RT_TypeDef_Instance::ResolveToken(
                 else
                 {
                     // elem.DataType == DATATYPE_MVAR
+
+                    // Use the *caller's* bound genericType (Stack<Int32>, etc.)
+                    if (caller == nullptr || caller->genericType == nullptr)
+                    {
+                        return false;
+                    }
+
                     CLR_RT_GenericParam_Index gpIdx;
                     caller->assembly->FindGenericParamAtMethodDef(*caller, elem.GenericParamPosition, gpIdx);
                     auto &gp = caller->assembly->crossReferenceGenericParam[gpIdx.GenericParam()];