Relax ErrorDetailsValues types matching (#1005)

Current checks is too strict, because it requires types to match
exactly to be assignable. Relax that, so that it can be assigned
to any matching interface.

internal/error_test.go

@@ -47,13 +47,21 @@ type testStruct2 struct {
 	Favorites *[]string
 }
 
+type testErrorStruct struct {
+	message string
+}
+
 var (
 	testErrorDetails1 = "my details"
 	testErrorDetails2 = 123
 	testErrorDetails3 = testStruct{"a string", 321}
 	testErrorDetails4 = testStruct2{"a string", 321, &[]string{"eat", "code"}}
 )
 
+func (tes *testErrorStruct) Error() string{
+	return tes.message
+}
+
 func Test_GenericError(t *testing.T) {
 	// test activity error
 	errorActivityFn := func() error {
@@ -411,6 +419,14 @@ func TestErrorDetailsValues_WrongDecodedType(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestErrorDetailsValues_AssignableType(t *testing.T) {
+	e := ErrorDetailsValues{&testErrorStruct{message: "my message"}}
+	var errorOut error
+	err := e.Get(&errorOut)
+	require.NoError(t, err)
+	require.Equal(t, "my message", errorOut.Error())
+}
+
 func Test_SignalExternalWorkflowExecutionFailedError(t *testing.T) {
 	context := &workflowEnvironmentImpl{
 		decisionsHelper: newDecisionsHelper(),

internal/workflow_testsuite.go

@@ -103,7 +103,7 @@ func (b ErrorDetailsValues) Get(valuePtr ...interface{}) error {
 	for i, item := range valuePtr {
 		target := reflect.ValueOf(item).Elem()
 		val := reflect.ValueOf(b[i])
-		if target.Type() != val.Type() {
+		if !val.Type().AssignableTo(target.Type()) {
 			return fmt.Errorf(
 				"unable to decode argument: cannot set %v value to %v field", val.Type(), target.Type())
 		}