Imported Upstream version 3.6.0

Former-commit-id: da6be194a6b1221998fc28233f2503bd61dd9d14

mcs/errors/cs0278.cs

@@ -0,0 +1,31 @@
+// CS0278: `Testing.IMixedEnumerable' contains ambiguous implementation of `enumerable' pattern. Method `System.Collections.IEnumerable.GetEnumerator()' is ambiguous with method `Testing.ICustomEnumerable.GetEnumerator()'
+// Line: 28
+// Compiler options: -warnaserror -warn:2
+
+using System;
+using System.Collections;
+
+namespace Testing {
+        interface ICustomEnumerable {
+                IEnumerator GetEnumerator();
+        }
+
+        interface IMixedEnumerable : IEnumerable, ICustomEnumerable {}
+
+        class TestCollection : IMixedEnumerable {
+                IEnumerator IEnumerable.GetEnumerator() {
+                        return null;
+                }
+
+                IEnumerator ICustomEnumerable.GetEnumerator()  {
+                        return null;
+                }
+        }
+
+        class Test {
+                public static void Main(string[] args) {
+                        IMixedEnumerable c = new TestCollection();
+                        foreach(object o in c) {}
+                }
+        }
+}