Implement Serialize and Deserialize for oxidized types

Summary: This will be a must-have for emitting and reading JSON for any of these types (notably, errors!). Somehow we haven't needed this yet.

Reviewed By: 2BitSalute, jewelpit

Differential Revision: D18843275

fbshipit-source-id: cc61ece79e5ced03f19bee8eaed81508b8d1aec3

Fix couldBe operator in HHBBC around mismatched array data

Summary:
HHBBC incorrectly reports that types like PArr([Int]) and
PArr([Obj]) cannot could be each other. This is false, as their
intersection contains the empty array. The reason is because the
"couldBe" operator is always checking the data, and if they do not
overlap, returning false. We don't want to check the data if the bit
intersection contains the empty array because we already have a valid
intersection. We already deal with this properly for optional types,
so do the same for empty arrays. The only complication is array
provenance. In the special case where both arrays have static array
corresponding to the empty array, the data actually corresponds to the
BArrLikeE bits, so we need to check that. Update the comment to
indicate this isn't just an optimization.

Reviewed By: markw65

Differential Revision: D19374431

fbshipit-source-id: a803acde40fd8c613268de2b6d58877e3765a50a

Releasing 4.40.0

use transDB to find TransRec given TC address

Summary: TransDB can be a better way to get php stack trace, as it contains more information. This diffs adds ability to do the lookup from a TCA in the middle of the translation.

Reviewed By: ottoni

Differential Revision: D19323702

fbshipit-source-id: a740e502716bb3ee6aacefe5c23555008835e453

Back out "Split LdWHResult into LdWHResult and LdWHException"

Summary: Reverting, as it causes segfaults.

fbshipit-source-id: e3c58fcdc01c40c8e602101338c713214d473ce7

Split LdWHResult into LdWHResult and LdWHException

Summary:
There are semantical differences between these two operations. This allows us
to optimize away LdWHException on a statically succeeded WH, as that can't
possibly happen.

Reviewed By: oulgen

Differential Revision: D19352858

fbshipit-source-id: b76530c19654c8d27c73ba1b2036f8122a71c769

Add interface file `clientLsp.mli`

Summary: Adding an interface file lets us know if there are elements of sum types which are constructed but never used or vice-versa. This catches an unnecessary variant case in the next diff.

Reviewed By: 2BitSalute

Differential Revision: D19332070

fbshipit-source-id: 81351fd9901e15f048ce9507f65aba39027ac537

fix reified_generics/shape-resolution-1.php test (facebook#8640)

Summary:
It should test the resolution of the class constant `C::foo`, not the literal string "C::foo".

I needed some small change for an end-to-end test of my new "open-source OnDemand" flow, this worked nicely :)
Pull Request resolved: facebook#8640

Reviewed By: oulgen

Differential Revision: D19319575

Pulled By: jjergus

fbshipit-source-id: a51c24097b04de6902fe73df24fcae257765c921

Remove editor-plugins directory (facebook#8634)

Summary:
The reason for the removal of this directory is that it contains a readme file that redirects us to [Hack Editor Plugins](https://github.com/facebook/hhvm/wiki/Hack-Editor-Plugins), which in turn redirects us to [Getting Started: Tools](https://docs.hhvm.com/hack/getting-started/tools) on the main page.
Pull Request resolved: facebook#8634

Differential Revision: D19304240

fbshipit-source-id: 23dce6a1cba8b85b1c558c44987b9af54da25dfd

Releasing 4.39.0