check for assignment to final field inside lambda (IDEA-123308)

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/HighlightControlFlowUtil.java

@@ -582,7 +582,7 @@ public class HighlightControlFlowUtil {
     final PsiElement resolved = reference == null ? null : reference.resolve();
     PsiVariable variable = resolved instanceof PsiVariable ? (PsiVariable)resolved : null;
     if (variable == null || !variable.hasModifierProperty(PsiModifier.FINAL)) return null;
-    final boolean canWrite = canWriteToFinal(variable, expression, reference, containingFile);
+    final boolean canWrite = canWriteToFinal(variable, expression, reference, containingFile) && checkWriteToFinalInsideLambda(variable, reference) == null;
     if (readBeforeWrite || !canWrite) {
       final String name = variable.getName();
       String description = canWrite ?
@@ -661,6 +661,10 @@ public class HighlightControlFlowUtil {
       QuickFixAction.registerQuickFixAction(highlightInfo, QUICK_FIX_FACTORY.createVariableAccessFromInnerClassFix(variable, innerClass));
       return highlightInfo;
     }
+    return checkWriteToFinalInsideLambda(variable, context);
+  }
+
+  private static HighlightInfo checkWriteToFinalInsideLambda(PsiVariable variable, PsiJavaCodeReferenceElement context) {
     final PsiLambdaExpression lambdaExpression = PsiTreeUtil.getParentOfType(context, PsiLambdaExpression.class);
     if (lambdaExpression != null && !PsiTreeUtil.isAncestor(lambdaExpression, variable, true)) {
       final PsiElement parent = variable.getParent();

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/highlighting/IDEA123308.java

@@ -0,0 +1,14 @@
+class Test {
+  private final int a;
+
+  public Test() {
+    a = 1;
+    run(() -> {
+      <error descr="Cannot assign a value to final variable 'a'">a</error> = 2;
+    });
+  }
+
+  public void run(Runnable r) {
+    r.run();
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/LambdaHighlightingTest.java

@@ -99,6 +99,7 @@ public class LambdaHighlightingTest extends LightDaemonAnalyzerTestCase {
   public void testFinalInitializer() {doTest();}
   public void testBreakContinueInside() {doTest();}
   public void testSameLambdaParamNames() {doTest();}
+  public void testIDEA123308() {doTest();}
 
   private void doTest() {
     doTest(false);