core: add failing deeply nested orphan module test

I was worried about the implications of deeply nested orphaned modules
in the parent commit, so I added a test. It's failing but not quite like
I expected it to. Perhaps I've uncovered an unrelated bug here?

/cc @mitchellh

terraform/context_apply_test.go

@@ -2145,6 +2145,57 @@ func TestContext2Apply_destroyNestedModule(t *testing.T) {
 	}
 }
 
+func TestContext2Apply_destroyDeeplyNestedModule(t *testing.T) {
+	m := testModule(t, "apply-destroy-deeply-nested-module")
+	p := testProvider("aws")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+
+	s := &State{
+		Modules: []*ModuleState{
+			&ModuleState{
+				Path: []string{"root", "child", "subchild", "subsubchild"},
+				Resources: map[string]*ResourceState{
+					"aws_instance.bar": &ResourceState{
+						Type: "aws_instance",
+						Primary: &InstanceState{
+							ID: "bar",
+						},
+					},
+				},
+			},
+		},
+	}
+
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		State: s,
+	})
+
+	// First plan and apply a create operation
+	if _, err := ctx.Plan(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	state, err := ctx.Apply()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Test that things were destroyed
+	actual := strings.TrimSpace(state.String())
+	expected := strings.TrimSpace(`
+module.child.subchild.subsubchild:
+  <no state>
+	`)
+	if actual != expected {
+		t.Fatalf("bad: \n%s", actual)
+	}
+}
+
 func TestContext2Apply_destroyOutputs(t *testing.T) {
 	m := testModule(t, "apply-destroy-outputs")
 	h := new(HookRecordApplyOrder)

terraform/test-fixtures/apply-destroy-deeply-nested-module/child/main.tf

@@ -0,0 +1,3 @@
+module "subchild" {
+  source = "./subchild"
+}

terraform/test-fixtures/apply-destroy-deeply-nested-module/child/subchild/main.tf

@@ -0,0 +1,5 @@
+/*
+module "subsubchild" {
+  source = "./subsubchild"
+}
+*/

terraform/test-fixtures/apply-destroy-deeply-nested-module/child/subchild/subsubchild/main.tf

@@ -0,0 +1 @@
+resource "aws_instance" "bar" {}

terraform/test-fixtures/apply-destroy-deeply-nested-module/main.tf

@@ -0,0 +1,3 @@
+module "child" {
+  source = "./child"
+}