[PATCH] D72498: [clangd] Print underlying type for decltypes in hover

[Ilya Biryukov via Phabricator via cfe-commits]

ilya-biryukov added a comment.

In D72498#1816424 <https://reviews.llvm.org/D72498#1816424>, @lh123 wrote:

> Currently, I think that in most cases, showing both expanded (canonical) and spelled types is sufficient.
>
> > This has been used in ycmd for ~4 years without complaint. https://github.com/clangd/clangd/issues/58#issuecomment-507800970


That actually doesn't look bad. Maybe let's try doing that and see whether we'll get negative feedback?
That seems to give useful information in **all** cases, so at least it'll cover all use-cases even it's more verbose.

What do others think?

In D72498#1816668 <https://reviews.llvm.org/D72498#1816668>, @kadircet wrote:

> In D72498#1813989 <https://reviews.llvm.org/D72498#1813989>, @ilya-biryukov wrote:
>
> > In D72498#1813962 <https://reviews.llvm.org/D72498#1813962>, @sammccall wrote:
> >
> > >
> >
> >
> > I tend to disagree here. decltype is normally the last resort, so whatever it produces is probably super-obscure, would even expect it to be not representable in C++ in many cases.
>
>
> I was rather talking about the obscurity of the expression inside decltype vs the typedef alias. I believe it is a lot harder to make any assumptions on `decltype(callback)` compared to `IntMap` without seeing the underlying type.


Point taken, although I bet we could come up with examples of obscure results in both cases.

>> Would definitely be helpful. If you feel we have some room in hover, I would love to have that. But there's a balance to be made, see Sam's comments about canonical types being obscure. I agree on 50% of the cases :-)
> 
> I think this should be OK to spend some space, as it will only show up when needed. I believe `better` printing of canonical types is a different problem we should definitely solve.

Totally agree, improving printing of STL types would be huge, no matter whether they're canonical or not.


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