Code for reproducing exception described in http://stackoverflow.com/q/16797890/562906

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Reflection;

namespace ConsoleApplication1
{
    struct MyStruct
    {
        private readonly int _value;
        public MyStruct(int val) { this._value = val; }

        public override bool Equals(object obj) { return false; }
        public override int GetHashCode() { return base.GetHashCode(); }

        public static bool operator ==(MyStruct a, MyStruct b) { return false; }
        public static bool operator !=(MyStruct a, MyStruct b) { return false; }
    }

    struct MyGenericStruct<T>
    {
        private readonly int _value;
        public MyGenericStruct(int val) { this._value = val; }

        public override bool Equals(object obj) { return false; }
        public override int GetHashCode() { return base.GetHashCode(); }

        public static bool operator ==(MyGenericStruct<T> a, MyGenericStruct<T> b) { return false; }
        public static bool operator !=(MyGenericStruct<T> a, MyGenericStruct<T> b) { return false; }
    }


    class Program
    {
        // Utility method for declaring Expression<Func<..>> without typing out the entire type each time
        static Expression<Func<T, U, bool>> MakeExpr<T, U>(Expression<Func<T, U, bool>> expr)
        {
            return expr;
        }

        static void Main(string[] args)
        {
            // Non generic struct
            Expression<Func<MyStruct, MyStruct, bool>> exprA   = 
                (valueA, valueB) => valueA == valueB;

            Expression<Func<MyStruct?, MyStruct?, bool>> exprB = 
                (nullableValueA, nullableValueB) => nullableValueA == nullableValueB;

            Expression<Func<MyStruct?, MyStruct, bool>> exprC  = 
                (nullableValueA, valueB) => nullableValueA == valueB;

            // Generic struct
            Expression<Func<MyGenericStruct<int>, MyGenericStruct<int>, bool>> exprGA =
                (valueA, valueB) => valueA == valueB;

            Expression<Func<MyGenericStruct<int>?, MyGenericStruct<int>?, bool>> exprGB =
                (nullableValueA, nullableValueB) => nullableValueA == nullableValueB;

            // Causes InvalidOperationException:
            Expression<Func<MyGenericStruct<int>?, MyGenericStruct<int>, bool>> exprGC =
                (nullableValueA, valueB) => nullableValueA == valueB;
        }
    }
}