Steps to reproduce:

1) Download attached project 'NestedGenerics.zip' and open in Unity
2) Make sure Scripting Backend is 'IL2CPP' in Player Settings
3) Build and Run project on a device
4) Check logcat, after scene finishes loading Exception will be thrown: 'NotSupportedException: IL2CPP encountered a managed type which it cannot convert ahead-of-time. The type uses generic or array types which are nested beyond the maximum depth which can be converted'

Expected result: No Exceptions in logcat.
Actual result: Exception 'NotSupportedException: IL2CPP encountered a managed type which it cannot convert ahead-of-time. The type uses generic or array types which are nested beyond the maximum depth which can be converted' thrown in logcat.

Reproduced with:
5.5.3p1, 5.5.3p2, 5.6.0p3, 2017.1.0b2

Not reproduced with:
5.5.0p4, 5.5.3f1

Regression from:
5.5.3p1

DUT:
Samsung SM G925F (Galaxy S6 Edge), OS:6.0.1, CPU:arm64-v8a, GPU:Mali-T760, Build:samsung/zeroltexx/zerolte:6.0.1/MMB29K/G925FXXU5DQA7:user/release-keys

HUAWEI EVA L19, OS:7.0, CPU:arm64-v8a, GPU:Mali-T880, Build:HUAWEI/EVA-L19/HWEVA:6.0/HUAWEIEVA-L19/C432B182:user/release-keys

Fixed in: 5.5.3p4 and 5.6.1p1