Internal compiler error. (...) warning CS0162: Unreachable code detected

Questions & Answers
1

Most of times I get “Internal compiler error”, I just edit anything in any file so it will recompile and then it goes away. Restarting Unity is another way of doing that same thing: triggering the compiler.

This time nothing of that worked.

What could have happened?

2

SisterKy have already compiled a fine list for the “what could have happened” part.

The warning, at other hand, gives a very specific information about what did happen: “Unreachable code”. I think it is still a compiler bug because of this simple test which does reproduce the same error (which was coincidentally already mentioned by cowlinator elsewhere). Just create an empty project and add this file:

using UnityEngine;
using System.Collections;

public class test : MonoBehaviour
{
	const // simply remove this line, and error will disappear
		bool foo = false;
	
	void Start ()
	{
		StartCoroutine( bar() );
	}
	
	IEnumerator bar ()
	{
		yield return 0;
		
		if (foo)
		{
			yield return 0;
		}
		
		Debug.Log("finished!");
	}
}

Once you know where this little bug is located it becomes pretty simple to find many ways to go around it. One way is using static readonly instead of const.

3

changing something from const to static will certainly get rid of this warning, but it also changes the semantics of your code.

imo a better way to do this is to bracket the offending code between

#pragma warning disable 0429 and #pragma warning restore 0429.

(0429 is what worked for me, but you might need to use 0162).