[FIR] Only track assignment nodes for uncaught exception edges in CFG

UncaughtExceptionPath edges are used to influence smart-casting within
catch and finally blocks. Previously these edges were added from every
node which could throw an exception. But only assignment nodes influence
smart-casts by resetting inference back to some less specific type.
Therefore, instead of tracking every possible node which could throw an
exception - even though almost every statement node can - only add edges
from assignment nodes to catch and finally blocks. This fixes many
missing exception cases and also reduces the total number of incoming
edges to catch and finally blocks.

#KT-56872 Fixed

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/cfg/CFGNode.kt

@@ -32,8 +32,6 @@ sealed class CFGNode<out E : FirElement>(val owner: ControlFlowGraph, val level:
     @OptIn(CfgInternals::class)
     val id = owner.nodeCount++
 
-    open val canThrow: Boolean get() = false
-
     //   a ---> b ---> d
     //      \-> c -/
     // Normal CFG semantics: a, then either b or c, then d
@@ -653,27 +651,18 @@ class BinaryOrExitNode(owner: ControlFlowGraph, override val fir: FirBinaryLogic
 // ----------------------------------- Operator call -----------------------------------
 
 class TypeOperatorCallNode(owner: ControlFlowGraph, override val fir: FirTypeOperatorCall, level: Int) : CFGNode<FirTypeOperatorCall>(owner, level) {
-    override val canThrow: Boolean
-        get() = fir.operation == FirOperation.AS
-
     override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
         return visitor.visitTypeOperatorCallNode(this, data)
     }
 }
 
 class ComparisonExpressionNode(owner: ControlFlowGraph, override val fir: FirComparisonExpression, level: Int) : CFGNode<FirComparisonExpression>(owner, level) {
-    override val canThrow: Boolean
-        get() = true // TODO? only overridden compareTo
-
     override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
         return visitor.visitComparisonExpressionNode(this, data)
     }
 }
 
 class EqualityOperatorCallNode(owner: ControlFlowGraph, override val fir: FirEqualityOperatorCall, level: Int) : AbstractBinaryExitNode<FirEqualityOperatorCall>(owner, level) {
-    override val canThrow: Boolean
-        get() = true // TODO? only overridden equals
-
     override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
         return visitor.visitEqualityOperatorCallNode(this, data)
     }
@@ -696,9 +685,6 @@ class ConstExpressionNode(owner: ControlFlowGraph, override val fir: FirConstExp
 
 class CheckNotNullCallNode(owner: ControlFlowGraph, override val fir: FirCheckNotNullCall, level: Int)
     : CFGNode<FirCheckNotNullCall>(owner, level) {
-    override val canThrow: Boolean
-        get() = true
-
     override val isUnion: Boolean
         get() = true
 
@@ -714,9 +700,6 @@ class QualifiedAccessNode(
     override val fir: FirQualifiedAccessExpression,
     level: Int
 ) : CFGNode<FirQualifiedAccessExpression>(owner, level) {
-    override val canThrow: Boolean
-        get() = fir.toResolvedCallableSymbol() is FirPropertySymbol
-
     override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
         return visitor.visitQualifiedAccessNode(this, data)
     }
@@ -734,10 +717,6 @@ class ResolvedQualifierNode(
 
 class FunctionCallNode(owner: ControlFlowGraph, override val fir: FirFunctionCall, level: Int)
     : CFGNode<FirFunctionCall>(owner, level) {
-
-    override val canThrow: Boolean
-        get() = true
-
     override val isUnion: Boolean
         get() = true
 
@@ -768,9 +747,6 @@ class DelegatedConstructorCallNode(owner: ControlFlowGraph, override val fir: Fi
     override val isUnion: Boolean
         get() = true
 
-    override val canThrow: Boolean
-        get() = true // shouldn't matter since delegated constructor calls aren't wrapped in try-finally, but still
-
     override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
         return visitor.visitDelegatedConstructorCallNode(this, data)
     }
@@ -792,9 +768,6 @@ class ThrowExceptionNode(
     override val fir: FirThrowExpression,
     level: Int
 ) : CFGNode<FirThrowExpression>(owner, level) {
-    override val canThrow: Boolean
-        get() = true
-
     override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
         return visitor.visitThrowExceptionNode(this, data)
     }
@@ -910,9 +883,6 @@ class FakeExpressionEnterNode(owner: ControlFlowGraph, level: Int) : CFGNode<Fir
 // ----------------------------------- Smart-cast node -----------------------------------
 
 class SmartCastExpressionExitNode(owner: ControlFlowGraph, override val fir: FirSmartCastExpression, level: Int) : CFGNode<FirSmartCastExpression>(owner, level) {
-    override val canThrow: Boolean
-        get() = fir.resolvedType.isNothing
-
     override fun <R, D> accept(visitor: ControlFlowGraphVisitor<R, D>, data: D): R {
         return visitor.visitSmartCastExpressionExitNode(this, data)
     }