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FIR DFA: deprioritize branches with no reassignments in flow unions

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callBothLambdas({ x = "..." }, { x is Int })
  // the assignment always executes, so x is String | (String & Int);
  // the latter is always a subtype of the former so it can be ignored
This commit is contained in:
pyos
2022-11-07 15:18:46 +01:00
committed by teamcity
parent fd609416c6
commit 3436535e7a
5 changed files with 442 additions and 314 deletions
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compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/PersistentLogicSystem.kt
+9 -6
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@@ -121,12 +121,15 @@ abstract class PersistentLogicSystem(context: ConeInferenceContext) : LogicSyste
val variables = flows.flatMapTo(mutableSetOf()) { it.approvedTypeStatements.keys + it.directAliasMap.keys } - commonAliases.keys
val statements = variables.mapNotNull { variable ->
val statement = if (allExecute) {
// All input flows execute in some order. If none of them reassign the variable, then
// *all* sets of statements are true; otherwise the assignments might have happened in
// an arbitrary order, so only one set of statements is true depending on which assignment
// happened last (and the flows that don't reassign may or may not have executed after that).
val byAssignment = flows.groupByTo(mutableMapOf()) { it.assignmentIndex[variable] ?: -1 }.values
or(byAssignment.map { flowSubset -> and(flowSubset.map { it.getTypeStatement(variable) }) })
// All input flows execute in some order. If none of the flows reassign, i.e. the only key
// in `byAssignment` is `commonFlow`'s assignment index, then all statements are true.
// Otherwise, one of the assignments executed last, but we don't know which, and the flows
// that don't reassign should be ignored because they may have executed before or after that.
val byAssignment = flows.groupByTo(mutableMapOf()) { it.assignmentIndex[variable] ?: -1 }
if (byAssignment.size > 1) {
byAssignment.remove(commonFlow.assignmentIndex[variable] ?: -1)
}
or(byAssignment.values.map { flowSubset -> and(flowSubset.map { it.getTypeStatement(variable) }) })
} else {
// One input flow executes - one set of statements is true, others might be false.
or(flows.map { it.getTypeStatement(variable) })