Merge pull request #42602 from jaredpar/debug-failfast

Diagnostics for FailFast

src/Compilers/Core/Portable/InternalUtilities/FailFast.cs

@@ -32,12 +32,40 @@ internal static void OnFatalException(Exception exception)
             {
                 exception = aggregate.InnerExceptions[0];
             }
+
 #endif
+            DumpStackTrace(exception);
 
             Environment.FailFast(exception.ToString(), exception);
             throw ExceptionUtilities.Unreachable; // to satisfy [DoesNotReturn]
         }
 
+        /// <summary>
+        /// Dumps the stack trace of the exception and the handler to the console. This is useful
+        /// for debugging unit tests that hit a fatal exception
+        /// </summary>
+        [Conditional("DEBUG")]
+        private static void DumpStackTrace(Exception exception)
+        {
+            Console.WriteLine("Dumping info before call to failfast");
+            Console.WriteLine("Exception info");
+
+            for (Exception? current = exception; current is object; current = current!.InnerException)
+            {
+                Console.WriteLine(current.Message);
+                Console.WriteLine(current.StackTrace);
+                current = current.InnerException;
+            }
+
+#if !NET20 && !NETSTANDARD1_3
+            Console.WriteLine("Stack trace of handler");
+            var stackTrace = new StackTrace();
+            Console.WriteLine(stackTrace.ToString());
+#endif
+
+            Console.Out.Flush();
+        }
+
         /// <summary>
         /// Checks for the given <paramref name="condition"/>; if the <paramref name="condition"/> is <c>true</c>, 
         /// immediately terminates the process without running any pending <c>finally</c> blocks or finalizers