Bug 19702 - Null coalescing expression evaluated twice with nullable return type.
Summary: Null coalescing expression evaluated twice with nullable return type.
Status: RESOLVED FIXED
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: 3.4.0
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: ---
Assignee: Marek Safar
URL:
Depends on:
Blocks:
 
Reported: 2014-05-12 19:20 UTC by Miles
Modified: 2014-05-22 02:39 UTC (History)
3 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED FIXED

Description Miles 2014-05-12 19:20:27 UTC
In the below code, the Left() method is incorrectly executed twice.  The issue only appears to be happening for nullable types.


    class MainClass
    {
        private static int _count = 1;

        public static void Main(string[] args)
        {
            var x = Left() ?? Right();
        }

        private static DateTime? Left()
        {
            Console.Out.WriteLine("Execution " + _count++);
            return DateTime.Now;
        }

        private static DateTime? Right()
        {
            return DateTime.Now;
        }
    }
Comment 1 Zoltan Varga 2014-05-13 12:34:29 UTC
-> mcs.
Comment 2 Marek Safar 2014-05-22 02:39:04 UTC
Fixed in master