[java] redundant cast: don't suggest to remove cast in switch branches without expected type (IDEA-296622)

GitOrigin-RevId: 24bebef33ad6d01861a68df1470f2ed2f454c4c8

java/java-analysis-impl/src/com/intellij/psi/util/RedundantCastUtil.java

@@ -1,4 +1,4 @@
-// Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package com.intellij.psi.util;
 
 import com.intellij.codeInsight.AnnotationUtil;
@@ -736,8 +736,10 @@ public final class RedundantCastUtil {
       visitSwitchBlockSelector(expression);
 
       PsiType expectedTypeByParent = PsiTypesUtil.getExpectedTypeByParent(expression);
-      for (PsiExpression resultExpression : PsiUtil.getSwitchResultExpressions(expression)) {
-        addIfNarrowing(resultExpression, expectedTypeByParent);
+      if (expectedTypeByParent != null) {
+        for (PsiExpression resultExpression : PsiUtil.getSwitchResultExpressions(expression)) {
+          addIfNarrowing(resultExpression, expectedTypeByParent);
+        }
       }
 
       super.visitSwitchExpression(expression);

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/switchExpressions/RedundantCastInSwitchBranch.java

@@ -31,4 +31,12 @@ class RedundantCast {
       default -> new ArrayList<>();
     };
   }
+
+  void castForFunctionalExpression(String s) {
+    (switch (s) {
+      case "a" -> (Runnable)() -> System.out.println("a");
+      case "b" -> (Runnable)() -> System.out.println("b");
+      default -> throw new IllegalArgumentException();
+    }).run();
+  }
 }