PY-81936 Code unreachable under sys.version_info guards is not highlighted

(cherry picked from commit ea1c276b5648f0ca4237b770179b27d6c5ee1048)

IJ-MR-167790

GitOrigin-RevId: e76f0a1150903d9eb85141c6c4ac898f67584d3d

python/python-psi-impl/src/com/jetbrains/python/codeInsight/controlflow/ControlFlowCache.java

@@ -68,7 +68,7 @@ public final class ControlFlowCache {
   public static @NotNull PyDataFlow getDataFlow(@NotNull ScopeOwner element, @NotNull TypeEvalContext context) {
     // Cache will reset on psi modification, same as TypeEvalContext
     return PyUtil.getParameterizedCachedValue(element, context, (ctx) -> {
-      return new PyDataFlow(getControlFlow(element), context);
+      return new PyDataFlow(element, getControlFlow(element), context);
     });
   }
 }

python/python-psi-impl/src/com/jetbrains/python/codeInsight/controlflow/PyDataFlow.kt

@@ -2,19 +2,27 @@ package com.jetbrains.python.codeInsight.controlflow
 
 import com.intellij.codeInsight.controlflow.ControlFlow
 import com.intellij.codeInsight.controlflow.Instruction
+import com.intellij.openapi.util.Version
 import com.intellij.psi.PsiElement
 import com.intellij.psi.util.PsiTreeUtil
 import com.jetbrains.python.codeInsight.dataflow.scope.ScopeUtil
 import com.jetbrains.python.psi.*
 import com.jetbrains.python.psi.impl.PyEvaluator
+import com.jetbrains.python.psi.impl.PythonLanguageLevelPusher
+import com.jetbrains.python.psi.impl.stubs.evaluateVersionsForElement
 import com.jetbrains.python.psi.types.PyNeverType
 import com.jetbrains.python.psi.types.TypeEvalContext
 import org.jetbrains.annotations.ApiStatus
 import java.util.*
 
 @ApiStatus.Internal
-class PyDataFlow(controlFlow: ControlFlow, private val context: TypeEvalContext) : ControlFlow by controlFlow {
+class PyDataFlow(scopeOwner: ScopeOwner, controlFlow: ControlFlow, private val context: TypeEvalContext) : ControlFlow by controlFlow {
   private val reachability: BooleanArray = BooleanArray(instructions.size)
+  private val languageVersion = run {
+    val languageLevel = PythonLanguageLevelPusher.getLanguageLevelForFile(scopeOwner.containingFile)
+    Version(languageLevel.majorVersion, languageLevel.minorVersion, 0)
+  }
+
 
   init {
     buildReachability()
@@ -45,19 +53,25 @@ class PyDataFlow(controlFlow: ControlFlow, private val context: TypeEvalContext)
   private fun getReachableSuccessors(instruction: Instruction): Collection<Instruction> {
     if (instruction is CallInstruction && instruction.isNoReturnCall(context)) return emptyList()
     if (instruction is PyWithContextExitInstruction && !instruction.isSuppressingExceptions(context)) return emptyList()
-    return instruction.allSucc().filter { next: Instruction ->
-      if (next is ReadWriteInstruction && next.access.isAssertTypeAccess) {
-        val type = next.getType(context, null)
-        return@filter !(type != null && type.get() is PyNeverType)
+    return instruction.allSucc()
+      .filter { it.isReachableWithVersionChecks() }
+      .filter { next: Instruction ->
+        if (next is ReadWriteInstruction && next.access.isAssertTypeAccess) {
+          val type = next.getType(context, null)
+          return@filter !(type != null && type.get() is PyNeverType)
+        }
+        return@filter true
       }
-      return@filter true
-    }
   }
 
   fun isUnreachable(instruction: Instruction): Boolean {
     if (instruction.num() >= reachability.size) return false
     return !reachability[instruction.num()]
   }
+
+  private fun Instruction.isReachableWithVersionChecks(): Boolean {
+    return evaluateVersionsForElement(element ?: return true).contains(languageVersion)
+  }
 }
 
 /**

python/testSrc/com/jetbrains/python/inspections/PyUnreachableCodeInspectionTest.java

@@ -24,6 +24,19 @@ public class PyUnreachableCodeInspectionTest extends PyInspectionTestCase {
   public void testUnreachable() {
     runWithLanguageLevel(LanguageLevel.PYTHON26, () -> doTest());
   }
+
+  // PY-81936
+  public void testUnreachableWithLangLevel() {
+    runWithLanguageLevel(LanguageLevel.PYTHON310, () -> doTestByText("""
+import sys
+
+if sys.version_info < (2, 7):
+    <warning descr="This code is unreachable">print("Unreachable")</warning>
+
+if sys.version_info > (3, 11):
+    <warning descr="This code is unreachable">print("Unreachable")</warning>
+                   """));
+  }
   
   // PY-81947
   public void testAnyOrNoneAfterIsNotNoneCast(){