Test for bug 1077204: Because a foreach iteration variable of a value type is...

Test for bug 1077204: Because a foreach iteration variable of a value type is read-only, an invocation of a mutating method on its instance field of a value type should make a temp copy rather than mutate the field in-place (changeset 1367129)

Src/Compilers/CSharp/Test/Semantic/Semantics/ForEachTests.cs

@@ -949,6 +949,41 @@ void Foo(int i)
                 Diagnostic(ErrorCode.ERR_ForEachMissingMember, "i").WithArguments("int", "GetEnumerator"));
         }
 
+        [Fact(Skip = "Bug 1077204")]
+        [WorkItem(1077204)]
+        public void TestIterationVariableIsReadOnly()
+        {
+            const string source = @"
+using System;
+
+struct A
+{
+    public B B;
+
+    static void Main()
+    {
+        A[] array = { default(A) };
+
+        foreach (A a in array)
+        {
+            a.B.SetField(5);
+            Console.Write(a.B.Field);
+        }
+    }
+}
+
+struct B
+{
+    public int Field;
+
+    public void SetField(int value)
+    {
+        this.Field = value;
+    }
+}";
+            CompileAndVerify(source, expectedOutput: "0");
+        }
+
         [Fact]
         public void TestErrorModifyIterationVariable()
         {