Improve generic support

src/Adapter/MSTest.TestAdapter/Extensions/MethodInfoExtensions.cs

@@ -197,6 +197,42 @@ internal static void InvokeAsSynchronousTask(this MethodInfo methodInfo, object?
         }
     }
 
+    private static void InferGenerics(Type parameterType, Type argumentType, List<(Type ParameterType, Type Substitution)> result)
+    {
+        if (parameterType.IsGenericMethodParameter())
+        {
+            // We found a generic parameter. The argument type should be the substitution for it.
+            result.Add((parameterType, argumentType));
+            return;
+        }
+
+        if (!parameterType.ContainsGenericParameters)
+        {
+            // We don't have any generics.
+            return;
+        }
+
+        if (parameterType.GetElementType() is { } parameterTypeElementType &&
+            argumentType.GetElementType() is { } argumentTypeElementType)
+        {
+            // If we have arrays, we need to infer the generic types for the element types.
+            // For example, if parameterType is `T[]` and argumentType is `string[]`, we need to infer that `T` is `string`.
+            // So, we call InferGenerics with `T` and `string`.
+            InferGenerics(parameterTypeElementType, argumentTypeElementType, result);
+            return;
+        }
+        else if (parameterType.GenericTypeArguments.Length == argumentType.GenericTypeArguments.Length)
+        {
+            for (int i = 0; i < parameterType.GenericTypeArguments.Length; i++)
+            {
+                if (parameterType.GenericTypeArguments[i].ContainsGenericParameters)
+                {
+                    InferGenerics(parameterType.GenericTypeArguments[i], argumentType.GenericTypeArguments[i], result);
+                }
+            }
+        }
+    }
+
     // Scenarios to test:
     //
     // [DataRow(null, "Hello")]
@@ -228,26 +264,30 @@ private static MethodInfo ConstructGenericMethod(MethodInfo methodInfo, object?[
         for (int i = 0; i < parameters.Length; i++)
         {
             Type parameterType = parameters[i].ParameterType;
-            if (!parameterType.IsGenericMethodParameter() || arguments[i] is null)
+            if (!parameterType.ContainsGenericParameters || arguments[i] is null)
             {
                 continue;
             }
 
-            Type substitution = arguments[i]!/*Very strange nullability warning*/.GetType();
-            int mapIndexForParameter = GetMapIndexForParameterType(parameterType, map);
-            Type? existingSubstitution = map[mapIndexForParameter].Substitution;
-
-            if (existingSubstitution is null || substitution.IsAssignableFrom(existingSubstitution))
-            {
-                map[mapIndexForParameter] = (parameterType, substitution);
-            }
-            else if (existingSubstitution.IsAssignableFrom(substitution))
-            {
-                // Do nothing. We already have a good existing substitution.
-            }
-            else
+            var result = new List<(Type ParameterType, Type Substitution)>();
+            InferGenerics(parameterType, arguments[i]!/*Very strange nullability warning*/.GetType(), result);
+            foreach ((Type genericParameterType, Type substitution) in result)
             {
-                throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, Resource.GenericParameterConflict, parameterType.Name, existingSubstitution, substitution));
+                int mapIndexForParameter = GetMapIndexForParameterType(genericParameterType, map);
+                Type? existingSubstitution = map[mapIndexForParameter].Substitution;
+
+                if (existingSubstitution is null || substitution.IsAssignableFrom(existingSubstitution))
+                {
+                    map[mapIndexForParameter] = (genericParameterType, substitution);
+                }
+                else if (existingSubstitution.IsAssignableFrom(substitution))
+                {
+                    // Do nothing. We already have a good existing substitution.
+                }
+                else
+                {
+                    throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, Resource.GenericParameterConflict, parameterType.Name, existingSubstitution, substitution));
+                }
             }
         }