[659022] Resolve reduced expressions

mcs/mcs/nullable.cs

@@ -1118,7 +1118,7 @@ namespace Mono.CSharp.Nullable
 					// Reduce (left ?? null) to left OR (null-constant ?? right) to right
 					//
 					if (right.IsNull || lc != null)
-						return ReducedExpression.Create (lc != null ? right : left, this);
+						return ReducedExpression.Create (lc != null ? right : left, this).Resolve (ec);
 
 					right = Convert.ImplicitConversion (ec, right, ltype, loc);
 					type = ltype;
@@ -1136,7 +1136,7 @@ namespace Mono.CSharp.Nullable
 			// Reduce (null ?? right) to right
 			//
 			if (left.IsNull)
-				return ReducedExpression.Create (right, this);
+				return ReducedExpression.Create (right, this).Resolve (ec);
 
 			left = Convert.ImplicitConversion (ec, unwrap != null ? unwrap : left, rtype, loc);
 			type = rtype;

mcs/tests/gtest-333.cs

+using System;
+
+public static class Program
+{
+	private static void Main ()
+	{
+		Exception ex1 = null ?? new Exception ();
+		Exception ex2 = new Exception() ?? null;
+	}
+}