[cling] Remove support for declarations without 'auto' keyword

[devajithvs]

This Pull request:

Removes the implicit auto keyword support added in: 071d084 and 1f4a6dc

Changes or fixes:

This feature was deprecated in: #14645

Will update LLVM and squash the commits here before the final merge/decision.

Checklist:

• tested changes locally
• updated the docs (if necessary)

This PR fixes #

[github-actions]

Test Results

    13 files      13 suites   3d 1h 26m 43s ⏱️
 3 029 tests  3 027 ✅ 0 💤 2 ❌
33 856 runs  33 854 ✅ 0 💤 2 ❌

For more details on these failures, see this check.

Results for commit 7a46308.

♻️ This comment has been updated with latest results.

[dpiparo]

lgtm: thanks.

[hahnjo]

I am not sure we can do this right now: This is a big departure from CINT times and there are probably still tons of macros out there that rely on it. Initially we discussed only removing this for ROOT 7, did this decision change?

If we remove this, I think we can also get rid of a patch in Clang: root-project/llvm-project@fecc97d

[vgvassilev]

I take this with a grain of salt as I remember how much efforts I spent to turn the compiler infrastructure upside down to support this feature...

This is awesome. LGTM!

I'd still wait for the input of @pcanal.

[dpiparo]

This was deprecated in 6.32, i.e.

[hahnjo]

This was deprecated in 6.32, i.e.

Yes, but I don't think people will do every upgrade and especially not for old macros. This was discussed in the ROOT meeting back then when we agreed that it would only be removed for ROOT 7. I'm ok with revisiting this decision, but I'm against just merging a PR less than half a year after it was deprecated.

[hahnjo]

.

[guitargeek]

Why was this deprecation not mentioned in the 6.32 release notes? https://root.cern/doc/v632/release-notes.html

The standard procedure is: if you deprecate something, write it in the release notes, including the information on when it will be eventually removed (which is usually one release later). If we don't follow our own standard here, we'll have these discussions forever :(

[hahnjo]

including the information on when it will be eventually removed (which is usually one release later)

In this case it was discussed: It will be removed in ROOT 7.

[guitargeek]

Is that discussion documented somewhere?

[hahnjo]

Is that discussion documented somewhere?

Yes, in https://indico.cern.ch/event/1381548/

Regarding the deprecation auto auto: will break a lot of unnamed old macros, we should wait with removing until ROOT 7. We will start issuing deprecation messages starting from ROOT 6.32.

[pcanal]

I agree with Jonas that it is too soon. (Anecdotally, my fingers still rely on this feature when typing at the prompt and grumble at the 'spurrious' warning :) ).

[dpiparo]

I would like to link here this note #15368 (comment) by @devajithvs : once this is merged, PR #15368 will have to be reverted.