System.Linq.Expressions.Expression.ValidateTryAndCatchHaveSameType C# (CSharp) Method

        private static void ValidateTryAndCatchHaveSameType(Type type, Expression tryBody, ReadOnlyCollection<CatchBlock> handlers)
        {
            Debug.Assert(tryBody != null);
            // Type unification ... all parts must be reference assignable to "type"
            if (type != null)
            {
                if (type != typeof(void))
                {
                    if (!TypeUtils.AreReferenceAssignable(type, tryBody.Type))
                    {
                        throw Error.ArgumentTypesMustMatch();
                    }
                    foreach (CatchBlock cb in handlers)
                    {
                        if (!TypeUtils.AreReferenceAssignable(type, cb.Body.Type))
                        {
                            throw Error.ArgumentTypesMustMatch();
                        }
                    }
                }
            }
            else if (tryBody.Type == typeof(void))
            {
                //The body of every try block must be null or have void type.
                foreach (CatchBlock cb in handlers)
                {
                    Debug.Assert(cb.Body != null);
                    if (cb.Body.Type != typeof(void))
                    {
                        throw Error.BodyOfCatchMustHaveSameTypeAsBodyOfTry();
                    }
                }
            }
            else
            {
                //Body of every catch must have the same type of body of try.
                type = tryBody.Type;
                foreach (CatchBlock cb in handlers)
                {
                    Debug.Assert(cb.Body != null);
                    if (!TypeUtils.AreEquivalent(cb.Body.Type, type))
                    {
                        throw Error.BodyOfCatchMustHaveSameTypeAsBodyOfTry();
                    }
                }
            }
        }
    }