Print addresses in state mv errors

Using the addrTo after it has failed its check means <invalid>/no
address will be printed. Change this throughout, but particularly
add a test for the origin issue for this.

command/state_mv.go

@@ -139,7 +139,7 @@ func (c *StateMvCommand) Run(args []string) int {
 				diags = diags.Append(tfdiags.Sourceless(
 					tfdiags.Error,
 					msgInvalidTarget,
-					fmt.Sprintf("Cannot move %s to %s: the target must also be a module.", addrFrom, addrTo),
+					fmt.Sprintf("Cannot move %s to %s: the target must also be a module.", addrFrom, destAddr),
 				))
 				c.showDiagnostics(diags)
 				return 1
@@ -184,7 +184,7 @@ func (c *StateMvCommand) Run(args []string) int {
 				diags = diags.Append(tfdiags.Sourceless(
 					tfdiags.Error,
 					msgInvalidTarget,
-					fmt.Sprintf("Cannot move %s to %s: the target must also be a whole resource.", addrFrom, addrTo),
+					fmt.Sprintf("Cannot move %s to %s: the target must also be a whole resource.", addrFrom, destAddr),
 				))
 				c.showDiagnostics(diags)
 				return 1
@@ -231,7 +231,7 @@ func (c *StateMvCommand) Run(args []string) int {
 					diags = diags.Append(tfdiags.Sourceless(
 						tfdiags.Error,
 						msgInvalidTarget,
-						fmt.Sprintf("Cannot move %s to %s: the target must also be a resource instance.", addrFrom, addrTo),
+						fmt.Sprintf("Cannot move %s to %s: the target must also be a resource instance.", addrFrom, destAddr),
 					))
 					c.showDiagnostics(diags)
 					return 1

command/state_mv_test.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/mitchellh/cli"
 
 	"github.com/hashicorp/terraform/addrs"
@@ -148,6 +149,7 @@ func TestStateMv(t *testing.T) {
 }
 
 func TestStateMv_resourceToInstance(t *testing.T) {
+	// A single resource (no count defined)
 	state := states.BuildState(func(s *states.SyncState) {
 		s.SetResourceInstanceCurrent(
 			addrs.Resource{
@@ -236,6 +238,71 @@ test_instance.baz:
 	testStateOutput(t, backups[0], testStateMvOutputOriginal)
 }
 
+func TestStateMv_resourceToInstanceErr(t *testing.T) {
+	state := states.BuildState(func(s *states.SyncState) {
+		s.SetResourceInstanceCurrent(
+			addrs.Resource{
+				Mode: addrs.ManagedResourceMode,
+				Type: "test_instance",
+				Name: "foo",
+			}.Instance(addrs.IntKey(0)).Absolute(addrs.RootModuleInstance),
+			&states.ResourceInstanceObjectSrc{
+				AttrsJSON: []byte(`{"id":"bar","foo":"value","bar":"value"}`),
+				Status:    states.ObjectReady,
+			},
+			addrs.AbsProviderConfig{
+				Provider: addrs.NewDefaultProvider("test"),
+				Module:   addrs.RootModule,
+			},
+		)
+		s.SetResourceProvider(
+			addrs.Resource{
+				Mode: addrs.ManagedResourceMode,
+				Type: "test_instance",
+				Name: "bar",
+			}.Absolute(addrs.RootModuleInstance),
+			addrs.AbsProviderConfig{
+				Provider: addrs.NewDefaultProvider("test"),
+				Module:   addrs.RootModule,
+			},
+		)
+	})
+	statePath := testStateFile(t, state)
+
+	p := testProvider()
+	ui := new(cli.MockUi)
+	c := &StateMvCommand{
+		StateMeta{
+			Meta: Meta{
+				testingOverrides: metaOverridesForProvider(p),
+				Ui:               ui,
+			},
+		},
+	}
+
+	args := []string{
+		"-state", statePath,
+		"test_instance.foo",
+		"test_instance.bar[0]",
+	}
+
+	if code := c.Run(args); code == 0 {
+		t.Fatalf("expected error output, got:\n%s", ui.OutputWriter.String())
+	}
+
+	expectedErr := `
+Error: Invalid target address
+
+Cannot move test_instance.foo to test_instance.bar[0]: the target must also be
+a whole resource.
+
+`
+	errOutput := ui.ErrorWriter.String()
+	if errOutput != expectedErr {
+		t.Errorf("Unexpected diff.\ngot:\n%s\nwant:\n%s\n", errOutput, expectedErr)
+		t.Errorf("%s", cmp.Diff(errOutput, expectedErr))
+	}
+}
 func TestStateMv_instanceToResource(t *testing.T) {
 	state := states.BuildState(func(s *states.SyncState) {
 		s.SetResourceInstanceCurrent(