Build error: "An expression is too long or complex to compile"

Question

Every now and then when I build a specific solution, I'll get a random amount of "An expression is too long or complex to compile" in the Error List window. However, the only item the error points to is the specific project, not a file within the project or a specific LOC.

When I encounter this, I 'Clean' and then I restart VS and that seems to fix it. Any ideas on what is causing this?

This particular solution has 50 projects in it.

Answer 1

FYI, that error is characteristic of the compiler running out of stack space. Typically that happens when you throw a "deep recursion" problem at the compiler, like say,

int x = (1 + (1 + (1 + (1 + ......... + 1 ) + 1 ) + 1 ) + 1);

say, several thousand deep. The syntactic and semantic analyzers are both recursive-descent analyzers and therefore prone to running out of stack space in extreme scenarios.

I have no idea why shutting down and starting over would affect that, though. That is really strange.

If you get a solid repro, I'd love to see it. Either post it here, or enter a bug on Connect and we'll have a look at it. Without a solid repro though it is very hard to say what is going on here.

Answer 2

I got this error in one project when I switched from Visual Studio 2012 to Visual Studio Community 2013. In my case it was giant file (25k lines, not written by me) with had List<string[]> initialized by collection initializer.

Something like this:

public class Class
{

    public List<string[]> BigList
    {
        get
        {
            return new List<string[]>()
            {
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                .
                .
                .
                .
                .
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"}
            }
        }
    }
}

I changed it to string[][] and the project started to compile

public class Class
{

    public string[][] BigList
    {
        get
        {
            return new string[][]
            {
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                .
                .
                .
                .
                .
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"}
            }
        }
    }
}

Answer 3

When building you can see the the build output the last folder it checks before it fails. I removed the files in that folder and brought them back one by one. Finally found the issue. I dont know exactly what it is but it was a .aspx page with lots of HTML. It wasnt used often so I just removed it from the project and now it compiles.