Fix parser regressions of conditional expressions

[DoctorKrolic]

Fixes: #75074

[NicholasMoss]

Thanks for looking into this so quickly.

I've double checked all places our solution breaks and it seems to happen for the from in linq query expression too.

I've added full replication steps onto the original ticket #75074

[DoctorKrolic]

I looked through the list of all contextual keywords and I don't see other keywords, which might be problematic for us. When reviewing please also look through them and point out, if I missed something. Even if the scenario is not a regression, we better add a test or a few for it

[CyrusNajmabadi]

Do you have tests for await x and await(x) both inside and outside an async context?

[333fred]

Do we have tests for:

• global
• yield

[DoctorKrolic]

Added a test for global qualified name. As of yield, since it is only valid as a yield return and yield break statements, it cannot be a contextual keyword inside an expression. However, this gave me an idea: if we have something like x is X ? yield return 0 ... we can parse it a lot better we we consider x is X? yield as one statement and return 0 ... as another one with missing ; in between. This is actually true for most keywords that start a statement: if, while, for etc. For now I added 2 yield tests with the right shape to just swap the errors and parse result in the future, but when main branch targets 17.13, I'm gnna make a follow-up PR with imrpoved error recovery for such cases

[333fred]

@DoctorKrolic are you going to be able to address feedback, or should we pick this up the rest of the way?

[DoctorKrolic]

@333fred PTAL

[333fred]

@cston for a second review.

[jcouv]

LGTM Thanks (iteration 6)

[jcouv]

Thanks @DoctorKrolic !