Bug error DC0013 while reading data inside lambda

Unity 2020.10b11 / Entities 0.11.0-preview.7

It looks like I stumbled across a bug with Lambdas inside parallel jobs.
I'm trying to read a buffer element from a lambda inside a job.
It's only a read but I get this error message inside Unity (maybe I don't understand it correctly?!?)

error DC0013: Entities.ForEach Lambda expression writes to captured variable

Code (CSharp):

1.  
2. using System;
3. using Unity.Entities;
4.  
5. namespace Buggy
6. {
7.     public struct TestData : IBufferElementData
8.     {
9.         public int Value;
10.     }
11.  
12.     public class BuggySystem : SystemBase
13.     {
14.         protected override void OnUpdate()
15.         {
16.             BufferFromEntity<TestData> entityBuffer = GetBufferFromEntity<TestData>(true);
17.             DynamicBuffer<TestData> buffer = entityBuffer[Entity.Null];
18.             Entities
19.                 .WithReadOnly(buffer)
20.                 .ForEach((int entityInQueryIndex, int nativeThreadIndex, Entity entity) =>
21.             {
22.                 // error DC0013: Entities.ForEach Lambda expression writes to captured variable '<>9__1'. This is only supported when you use .Run().
23.                 Func<int, int> func = (index) => buffer[index].Value;
24.             }).ScheduleParallel();
25.         }
26.     }
27. }
28.  

Side note: When I debug Entities code with Rider, Unity freezes and becomes unresponsive like every second time.
It's quite painful... :/

Edit: I realized this is true for NativeArrays as well so I changed the title/description.