I.e. maintain a set of seen lambdas where each marked as either "data
flow only" or "both data and control flow". The latter are truly
parallel with the function being analyzed, while the former have
technically already terminated, we just don't know the types inside them
because they may not have been analyzed yet.
Quick quiz:
Q: In a CFG, what does `a -> b -> c -> d` mean?
A: `a`, then `b`, then `c`, then `d`.
Q: In a CFG, what does `a -> b -> d; a -> c -> d` mean?
A: `a`, then `b` or `c`, then `d`.
Q: So how do you encode "a, then (b, then c) or (c, then b), then d`?
A: You can't.
Problem is, you need to, because that's what `a; run2({ b }, { c }); d`
does when `run2` has a contract that it calls both its lambda arguments
in-place: `shuffle(listOf(block1, block2)).forEach { it() }` is a
perfectly valid implementation for it, as little sense as that makes.
So that's what union nodes solve. When a node implements
`UnionNodeMarker`, its inputs are interpreted as "all visited in some
order" instead of the normal "one of the inputs is visited".
Currently this is used for data flow. It *should* also be used for
control flow, but it isn't. But it should be. But that's not so easy.
BTW, `try` exit is NOT a union node; although lambdas in one branch can
be completed according to types' of lambdas in another, data does not
flow between the branches anyway (since we don't know how much of the
`try` executed before jumping into `catch`, and `catch`es are mutually
exclusive) so a `try` expression is more like `when` than a function
call with called-in-place-exactly-once arguments. The fact that
`exitTryExpression` used `processUnionOfArguments` in a weird way
should've hinted at that, but now we know for certain.
If a certain type statement is true on loop entry and all continue
paths, then it is also true on exit if the condition did not reassign
the variable.
^KT-7676 tag fixed-in-k2
It's also not a backwards jump in do-while, unless it's in the loop's
condition, which is a stupid "feature" IMO. As you can probably tell
from the comments added in this commit.
Previously, FIR used `_context_receiver_n` while FE10 used `<this>` for
all context receiver parameters. This commit changes the code in FE10
to follow the convention from FIR.
When serializing metadata for local delegated properties, we need to
find a valid container class where to put it, and where kotlin-reflect
will be able to find that metadata at runtime. Taking just the closest
class lexically doesn't work, because in the attached test, it is a
class for a lambda which does not have metadata and thus does not have a
way to store any extra information.
So, in 1663619606 we started to look for the closest "non-synthetic"
class to store this metadata. But apparently it was missed that script
is a valid container class. In the test, this meant that no
non-synthetic container classes were found to store the metadata, so we
falled back to using the closest class anyway (see `?: this` in
`rememberLocalProperty`), which turned out to be the lambda.
After this change, metadata for local delegated property in a lambda
will be stored in the script class, just like it's stored in the file
class in the non-script case.
#KT-55065 Fixed
Evgeniy.Zhelenskiy