Fixed handling of parameterless struct constructors in expression tree lowering.

  (changeset 1333851)

Src/Compilers/CSharp/Portable/Lowering/LambdaRewriter/ExpressionLambdaRewriter.cs

@@ -821,7 +821,9 @@ private BoundExpression VisitObjectCreationExpressionInternal(BoundObjectCreatio
                 return Constant(node);
             }
 
-            if ((object)node.Constructor == null || node.Arguments.Length == 0)
+            if ((object)node.Constructor == null || 
+                (node.Arguments.Length == 0 && !node.Type.IsStructType()) || 
+                node.Constructor.IsDefaultValueTypeConstructor())
             {
                 return ExprFactory("New", Bound.Typeof(node.Type));
             }

Src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenConstructorInitTests.cs

@@ -810,5 +810,30 @@ static void Main()
             CompileAndVerifyExperimental(source, expectedOutput: "0");
         }
 
+
+        [Fact]
+        public void InstanceInitializerStructInExprTree()
+        {
+            var source = @"
+
+using System;
+using System.Linq.Expressions;
+
+class C
+{
+    struct S1
+    {
+        public int x = 42;
+    }
+
+    static void Main()
+    {
+        Expression<Func<S1>> testExpr = () => new S1();
+        System.Console.Write(testExpr.Compile()().x);
+    }
+}
+";
+            CompileAndVerifyExperimental(source, additionalRefs: new[] { ExpressionAssemblyRef }, expectedOutput: "42");
+        }
     }
 }