failing test for cty conversion bug

builtin/providers/test/resource_config_mode.go

@@ -28,6 +28,24 @@ func testResourceConfigMode() *schema.Resource {
 					},
 				},
 			},
+			"nested_set": {
+				Type:       schema.TypeSet,
+				Optional:   true,
+				ConfigMode: schema.SchemaConfigModeAttr,
+				Elem: &schema.Resource{
+					Schema: map[string]*schema.Schema{
+						"value": {
+							Type:     schema.TypeString,
+							Optional: true,
+						},
+						"set": {
+							Type:     schema.TypeSet,
+							Optional: true,
+							Elem:     &schema.Schema{Type: schema.TypeString},
+						},
+					},
+				},
+			},
 		},
 	}
 }

builtin/providers/test/resource_config_mode_test.go

@@ -93,3 +93,28 @@ resource "test_resource_config_mode" "foo" {
 		},
 	})
 }
+
+func TestResourceConfigMode_nestedSet(t *testing.T) {
+	resource.UnitTest(t, resource.TestCase{
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckResourceDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: strings.TrimSpace(`
+resource "test_resource_config_mode" "foo" {
+	resource_as_attr = []
+
+	nested_set {
+		value = "a"
+	}
+	nested_set {
+		value = "b"
+		set = []
+	}
+}
+				`),
+				Check: resource.ComposeTestCheckFunc(),
+			},
+		},
+	})
+}