[3.x] Regression in GenericMethodInvoker with generic constraints

[niblak]

7185 (and subsequent changes) introduced a regression in GenericMethodInvoker when the method specifies a type constraint that is also itself generic. This used to work in Orleans 3.4.3, but will now throw Could not find exact match for generic method on 3.6.2.

I will submit a PR to address this in the 3.x branch. Looks like this code path has been removed in the main branch as part of the serializer improvements in 4.0. My project has not yet upgraded to 4.0 so I am not sure what if any changes need to be made there, but it would be good if someone could investigate whether this regression also exists in 4.0.

[ghost]

We're moving this issue to the 4.0-Planning milestone for future evaluation / consideration. Because it's not immediately obvious that this is a bug in our framework, we would like to keep this around to collect more feedback, which can later help us determine the impact of it. We will re-evaluate this issue, during our next planning meeting(s). If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.

[oising]

@niblak There's a high chance this "worked" before - in the sense that it threw no exceptions - but in reality would fail in more complex scenarios. In Orleans 3.4.x, the algorithm would always select the first match in any given overloaded generic method. I fixed this, but introduced new bugs! Thanks for tracking it down!

[ReubenBond]

Fixed by #7876