Update Pysa quickstart

Reviewed By: gbleaney

Differential Revision: D28416629

fbshipit-source-id: 8ebc243adc0a7e2bcd9823da34216724146c2de2

Reduce verbosity of overlapping buck target warning

Reviewed By: shannonzhu

Differential Revision: D28342186

fbshipit-source-id: 8c35b8c36ff60c305d01e3510b8b865ad0a6c005

Fix up comments on Define.Signature.t

Summary:
We had inline comments (by that I mean trailing comments) for fields in
Define.Signature.t, and in a refactor the autoformatter moved our comments for
us to the next line. This is bad because comments should always go above the
code, not below, and it was actually kind of disastrous in this case because
`parent` and `nesting_define` - the very things we wanted to the comment to
clearly distinguish - are right next to each other so the comment became a lie.

Anyway, patching up the comments to be above the record fields they refer to,
and also to be consistent across the .mli file, the signature, and the struct.

It's probably not a good idea for us to make too much use of inline comments
for this reason - autoformatting can easily drop them to a new line at which
point they go from being helpful to actively misleading.

To be honest I think this is an issue in the specification of `ocamlformat`,
moving an inline comment down is probably almost never the right thing to do.

Reviewed By: grievejia

Differential Revision: D28151440

fbshipit-source-id: 52dff080c158db0f54dbd6ddbba93307524d2dea

More actionable message for "server already exist" error

Reviewed By: shannonzhu

Differential Revision: D26838895

fbshipit-source-id: 978e5ed739267ed3f3388961e1cbb47f9fdf8635

improve error messages when loading from saved state fails

Summary: As titled.

Reviewed By: grievejia

Differential Revision: D26836065

fbshipit-source-id: 6330a1e1701035d04e9a9bc99be5a0d2187d3473

Resolve concatenation of tuples via unpacking.

Summary:
Problem: We used to resolve `(1, *(2, 3))` as `Tuple[int, unknown]`. This was because we correctly resolved `(2, 3)` as `Tuple[int, int]` and then dropped the ball on the `Starred` expression because there is no type to express a naked unpacked tuple.

With variadic tuples, we can handle different kinds of unpacked tuples.

Reviewed By: dkgi

Differential Revision: D26821042

fbshipit-source-id: 7aad420ca4b2775e32617077a4f1d0e965efff30

added pysa vscode extension template (facebook#388)

Summary:
Cloned Pyre's existing VSCode extension code and changed README, package.json for Pysa. This sets up a template for further development of extension and completes [Step https://github.com/facebook/pyre-check/issues/1](https://github.com/MLH-Fellowship/pyre-check/issues/2) in the overall roadmap to creating a Language Server extension for Pysa.

Pull Request resolved: facebook#388

Reviewed By: arthaud

Differential Revision: D26781032

Pulled By: gbleaney

fbshipit-source-id: 67e0d954133d517ec7f8a8be60471a51cd76f9a1

update documentation for ocaml 4.10.2

Summary: We upgraded our version of ocaml but did not update the documentation. Let's fix it.

Reviewed By: grievejia

Differential Revision: D26674077

fbshipit-source-id: 96f7b30b666b1fb6520f34df7c5e9ab4c701edf5

Add pyre badge to readme (facebook#371)

Summary: Pull Request resolved: facebook#371

Reviewed By: pradeep90

Differential Revision: D25927938

Pulled By: dkgi

fbshipit-source-id: 180e970acf39bb947b6a116c631900e08a3b2fb1

support source-specific sanitizers

Summary: Does what it says on the tin. For the syntax, I chose to support parsing our existing `TaintSource[...]` syntax, as it already had support for multiple kinds of taint.

Reviewed By: arthaud

Differential Revision: D24853422

fbshipit-source-id: 857747d8246cde76501481378a6b7cf2e7072a2c