Hiding errorx.TypeModifierTransparent forbids the following use case:

// transparent wrapper without stacktrace
var errWrapper = errorx.CommonErrors.NewType("wrapper").
	ApplyModifiers(errorx.TypeModifierTransparent, errorx.TypeModifierOmitStackTrace)

...
// like `errorx.Decorate` but guarantees that no stack trace will be added
return errWrapper.Wrap(io.EOF, "additional message")

There are four ways to enable it:

1. Leave errorx.TypeModifierTransparent public thus keeping status quo
2. Add errorx.TransparentWrapperWithoutStacktrace error type
3. Add errorx.DecorateWithNoStackTrace helper func
4. Declare this use case as marginal and leave users to resort to errorx.ErrorBuilder

@g7r I can see no benefit from transparency in this particular example.
If you want to have a wrapper with no stack trace around io.EOF, wrap with a private type suits your needs. There is no way to check against io.EOF wrapped in errorx error anyway, other than manually unroll the Cause chain, and you can do so even through opaque wrap.

I could conjure up another example that would be trickier in this regard, but if we struggle to find one, then I'd stick to option 4 just now.

@g7r I can see no benefit from transparency in this particular example.
If you want to have a wrapper with no stack trace around io.EOF, wrap with a private type suits your needs. There is no way to check against io.EOF wrapped in errorx error anyway, other than manually unroll the Cause chain, and you can do so even through opaque wrap.

I could conjure up another example that would be trickier in this regard, but if we struggle to find one, then I'd stick to option 4 just now.

errWrapper wraps external-type errors without stacktrace and transparently wraps errorx-type errors. However it would be more honest if both types of errors will be wrapped opaquely. Therefore I should drop TypeModifierTransparent from error type above. OK.

We seem to have abandoned this PR.
I suggest either to close it or to think it over again and come up with some sort of revised summary, to use it as a new starting point for discussion.