[FIR] Fix data-flow after while loops

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt

@@ -392,6 +392,19 @@ abstract class FirDataFlowAnalyzer<FLOW : Flow>(
 
     // ----------------------------------- While Loop -----------------------------------
 
+    private fun exitCommonLoop(exitNode: LoopExitNode) {
+        val singlePreviousNode = exitNode.previousNodes.singleOrNull { !it.isDead }
+        if (singlePreviousNode is LoopConditionExitNode) {
+            val variable = variableStorage.getOrCreateVariable(singlePreviousNode.fir)
+            exitNode.flow = logicSystem.approveStatementsInsideFlow(
+                exitNode.flow,
+                variable eq false,
+                shouldForkFlow = false,
+                shouldRemoveSynthetics = true
+            )
+        }
+    }
+
     fun enterWhileLoop(loop: FirLoop) {
         val (loopEnterNode, loopConditionEnterNode) = graphBuilder.enterWhileLoop(loop)
         loopEnterNode.mergeIncomingFlow()
@@ -407,7 +420,7 @@ abstract class FirDataFlowAnalyzer<FLOW : Flow>(
                 loopBlockEnterNode.flow,
                 conditionVariable eq true,
                 shouldForkFlow = false,
-                shouldRemoveSynthetics = true
+                shouldRemoveSynthetics = false
             )
         }
     }
@@ -416,6 +429,7 @@ abstract class FirDataFlowAnalyzer<FLOW : Flow>(
         val (blockExitNode, exitNode) = graphBuilder.exitWhileLoop(loop)
         blockExitNode.mergeIncomingFlow()
         exitNode.mergeIncomingFlow()
+        exitCommonLoop(exitNode)
     }
 
     // ----------------------------------- Do while Loop -----------------------------------
@@ -436,6 +450,7 @@ abstract class FirDataFlowAnalyzer<FLOW : Flow>(
         val (loopConditionExitNode, loopExitNode) = graphBuilder.exitDoWhileLoop(loop)
         loopConditionExitNode.mergeIncomingFlow()
         loopExitNode.mergeIncomingFlow()
+        exitCommonLoop(loopExitNode)
     }
 
     // ----------------------------------- Try-catch-finally -----------------------------------

compiler/testData/diagnostics/tests/BreakContinue.fir.kt

@@ -38,7 +38,7 @@ class C {
                 break;
             }
         }
-        a.<!INAPPLICABLE_CANDIDATE!>compareTo<!>("2")
+        a.compareTo("2")
     }
 
     fun containsBreakWithLabel(a: String?) {
@@ -52,7 +52,7 @@ class C {
         loop@ while(a == null) {
             break@label
         }
-        a.<!INAPPLICABLE_CANDIDATE!>compareTo<!>("2")
+        a.compareTo("2")
     }
 
     fun containsBreakToOuterLoop(a: String?, b: String?) {
@@ -60,7 +60,7 @@ class C {
             while(a == null) {
                 break@loop
             }
-            a.<!INAPPLICABLE_CANDIDATE!>compareTo<!>("2")
+            a.compareTo("2")
         }
     }
 

compiler/testData/diagnostics/tests/Nullability.fir.kt

@@ -151,7 +151,7 @@ fun test() {
     out2?.println();
     out2.<!INAPPLICABLE_CANDIDATE!>println<!>();
   }
-  out2.<!INAPPLICABLE_CANDIDATE!>println<!>()
+  out2.println()
 
 }
 
@@ -228,7 +228,7 @@ fun f6(s : String?) {
   do {
     s?.get(0)
   } while (s == null)
-  s.<!INAPPLICABLE_CANDIDATE!>get<!>(0)
+  s.get(0)
 }
 
 fun f7(s : String?, t : String?) {

compiler/testData/diagnostics/tests/infos/SmartCasts.fir.kt

@@ -127,12 +127,12 @@ fun f13(a : A?) {
 fun f14(a : A?) {
   while (!(a is B)) {
   }
-  a.<!UNRESOLVED_REFERENCE!>bar<!>()
+  a.bar()
 }
 fun f15(a : A?) {
   do {
   } while (!(a is B))
-  a.<!UNRESOLVED_REFERENCE!>bar<!>()
+  a.bar()
 }
 
 fun getStringLength(obj : Any) : Char? {

compiler/testData/diagnostics/tests/smartCasts/loops/doWhileNull.fir.kt

@@ -1,5 +1,5 @@
 fun foo(s: String?): Int {
     do {
     } while (s==null)
-    return s.<!INAPPLICABLE_CANDIDATE!>length<!>
+    return s.length
 }

compiler/testData/diagnostics/tests/smartCasts/loops/nestedDoWhile.fir.kt

@@ -7,7 +7,7 @@ public fun foo(p: String?, r: String?): Int {
         } while (r == null)  
     } while (!x())
     // Auto cast possible
-    r.<!INAPPLICABLE_CANDIDATE!>length<!>
+    r.length
     // Auto cast possible
     return p.length
 }

compiler/testData/diagnostics/tests/smartCasts/loops/nestedDoWhileWithLongContinue.fir.kt

@@ -8,7 +8,7 @@ public fun foo(p: String?, r: String?): Int {
         } while (r == null)  
     } while (!x())
     // Auto cast NOT possible due to long continue
-    r.<!INAPPLICABLE_CANDIDATE!>length<!>
+    r.length
     // Auto cast possible
     return p.length
 }

compiler/testData/diagnostics/tests/smartCasts/loops/nestedLoops.fir.kt

@@ -11,7 +11,7 @@ public fun foo(p: String?, r: String?, q: String?): Int {
         if (!x()) break
     }
     // Smart cast is possible everywhere
-    r.<!INAPPLICABLE_CANDIDATE!>length<!>
+    r.length
     q.length
     return p.length
 }

compiler/testData/diagnostics/tests/smartCasts/loops/nestedLoopsShort.fir.kt

@@ -9,7 +9,7 @@ public fun foo(p: String?, r: String?, q: String?): Int {
         if (!x()) break
     }
     // Smart cast is possible everywhere
-    r.<!INAPPLICABLE_CANDIDATE!>length<!>
+    r.length
     q.length
     return p.length
 }

compiler/testData/diagnostics/tests/smartCasts/loops/nestedLoopsWithBreak.fir.kt

@@ -12,7 +12,7 @@ public fun foo(p: String?, r: String?, q: String?): Int {
         if (!x()) break
     }
     // Smart cast is possible everywhere
-    r.<!INAPPLICABLE_CANDIDATE!>length<!>
+    r.length
     q.length
     return p.length
 }

compiler/testData/diagnostics/tests/smartCasts/loops/nestedLoopsWithLongContinue.fir.kt

@@ -14,6 +14,6 @@ public fun foo(p: String?, r: String?, q: String?): Int {
     // Smart cast is possible only for q
     q.length
     // But not possible for the others
-    r.<!INAPPLICABLE_CANDIDATE!>length<!>
+    r.length
     return p.length
 }

compiler/testData/diagnostics/tests/smartCasts/loops/whileNull.fir.kt

@@ -1,5 +1,5 @@
 fun foo(s: String?): Int {
     while (s==null) {
     }
-    return s.<!INAPPLICABLE_CANDIDATE!>length<!>
+    return s.length
 }

compiler/testData/diagnostics/tests/smartCasts/loops/whileNullAssignToSomething.fir.kt

@@ -5,5 +5,5 @@ fun main() {
         if (i == 10) result = "non null"
         else i++
     }
-    result.<!INAPPLICABLE_CANDIDATE!>length<!>
+    result.length
 }

compiler/testData/diagnostics/tests/smartCasts/variables/ifElseBlockInsideDoWhile.fir.kt

@@ -11,5 +11,5 @@ public fun foo(xx: Any): Int {
         // y!! in both branches
         y.length
     } while (!(x is String))
-    return x.<!UNRESOLVED_REFERENCE!>length<!>
+    return x.length
 }

compiler/testData/diagnostics/tests/smartCasts/varnotnull/nestedDoWhile.fir.kt

@@ -9,7 +9,7 @@ public fun foo(pp: String?, rr: String?): Int {
         } while (r == null)  
     } while (!x())
     // Auto cast possible
-    r.<!INAPPLICABLE_CANDIDATE!>length<!>
+    r.length
     // Auto cast possible
     return p.length
 }