function enter -> default 1 -> default 2 -> rest of function
\----------^ \----------^
This probably has no effect (in non-stupid code, at least), but it makes
graph construction more architecturally correct (now value parameters'
subgraphs get attached to a node).
Interpretation: a graph A is a subgraph of B if information available at
nodes of A depends on the paths taken in B. For example, local classes
are subgraphs of a graph in which they are declared, and members of
those classes are subgraphs of the local class itself - because these
members can reference captured values.
Consequences:
* if graph G is a subgraph of node N, then G is a subgraph of N's
owner;
* `ControlFlowAnalysisDiagnosticComponent` will only visit root graphs;
* `graph.traverse` will ignore subgraph boundaries, as if all subgraphs
are inlined into one huge root graph;
* if a control flow checker needs information from a declaration to
which a graph is attached, it must look at subgraphs explicitly.
For example, consider the `callsInPlace` checker. When a function
has a `callsInPlace` contract and a local declaration, the checker must
visit that local declaration to ensure it does not capture the allegedly
called-in-place argument - hence `graph.traverse` will look at the
nodes. However, the local declaration can also be a function with its
own `callsInPlace` contracts, so the checker should also run for it in
isolation. If that sounds quadratic, that's because unfortunately it is.
useCorrectedNullabilityForTypeParameters = true only might lead
to something becomes a DNN when otherwise it wasn't.
It seems safe to use it here, since if compiler has generated DNN, then
it's OK to assume that it checked necessary conditions, and it's likely
that it had useCorrectedNullabilityForTypeParameters = true as well, there.
Anyway, it looks saner than having an exception here.
Also, we assume here that metadata leading to exception might only be generated
with ProhibitUsingNullableTypeParameterAgainstNotNullAnnotated LF
(at least, we don't have contradicting evidences),
thus it's mostly a preparations in case we decide to enable
ProhibitUsingNullableTypeParameterAgainstNotNullAnnotated in 1.9.
^KT-55357 Fixed
^KT-55388 Related
^KT-36770 Related
Previously, it worked by default because ProhibitUsingNullableTypeParameterAgainstNotNullAnnotated
was enabled by default since 1.8, but we have to disable it because of KT-55357
Turning off the fix by default is not a breaking change per se, because
1.8 has not yet been released.
^KT-55357 Related
^KT-36770 Related
^KT-53041 Open
This feature is not needed because it is unconditionally disabled for K1
(because of not fully correct implementation) and unconditionally enabled
in K2 (K2 does not support old behavior)
^KT-38895
In K1 analogue of `K2_VISIBILITY_ERROR` is `K1_RUNTIME_ERROR`, so
candidates with `K2_VISIBILITY_ERROR` should win over innaplicable
candidates with `INAPPLICABLE`, `INAPPLICABLE_ARGUMENTS_MAPPING_ERROR`
or `INAPPLICABLE_WRONG_RECEIVER` applicability
This is needed to allow resolution to invisible symbols (and later
suppress error with `@Suppress("INVISIBLE_SYMBOL", "INVISIBLE_REFERENCE")`
^KT-55026 Fixed
^KT-55234
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.
pyos