GROOVY-7971: @CS flow typing incorrectly casting to map at runtime

[paulk-asert]

No description provided.

[eric-milles]

Does this change accommodate checking instanceof under a ternary expression or as part of a larger boolean expression?

int m(o) { (o instanceof List || o instanceof Map ? o.size() : 1) } // or def x = (o instanceof List || o instanceof Map) && o.isEmpty()

#1269 is not specific to if/else, but as you noted is more restrictive.

Does this change fix the runtime cast exception of your Deque vs. Stack example under static compilation?

[paulk-asert]

@eric-milles No, those cases aren't covered but the if case is. The Stack/Deque case is one of the test cases. The full solution I think will require us to push through Union and Intersection types (though I don't like those names) throughout. I started doing that but never finished. There are lots of hidden assumptions about the current approach throughout the codebase and will take some time. I see this as fixing up a common case while we work longer on the more complete solution. With the if in place, I believe we could have workarounds for the other cases. We could target them as special cases too but it makes the codebase messier the more of these hacks we have.

[daniellansun]

PR #1269 or PR #1293 ?

[daniellansun]

The PR seems to break Grails joint build:
https://github.com/apache/groovy/runs/836663285?check_suite_focus=true