From ec42e3be577c5c7929298529831a82cec433fac6 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <tagir.valeev@jetbrains.com>
Date: Tue, 30 Apr 2024 14:36:32 +0200
Subject: [PATCH] [java-inspections] Do not report redundant cast if any of
 labels is incompatible with the selector expression

Fixes IDEA-352510 False positive 'redundant cast' warning in switch

GitOrigin-RevId: b31e6f906bebb9de15c82439006502cc8e01f76f
---
 .../com/intellij/psi/util/RedundantCastUtil.java | 16 +++++++++++++++-
 .../inspection/redundantCast/SwitchUnboxing.java | 10 ++++++++++
 .../RedundantCastInspectionTest.java             |  2 ++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 java/java-tests/testData/inspection/redundantCast/SwitchUnboxing.java

diff --git a/java/java-analysis-impl/src/com/intellij/psi/util/RedundantCastUtil.java b/java/java-analysis-impl/src/com/intellij/psi/util/RedundantCastUtil.java
index 57ccbdbc73d0..31f82fd4418d 100644
--- a/java/java-analysis-impl/src/com/intellij/psi/util/RedundantCastUtil.java
+++ b/java/java-analysis-impl/src/com/intellij/psi/util/RedundantCastUtil.java
@@ -22,6 +22,7 @@ import com.intellij.util.containers.ContainerUtil;
 import com.siyeh.ig.bugs.NullArgumentToVariableArgMethodInspection;
 import com.siyeh.ig.psiutils.ExpectedTypeUtils;
 import com.siyeh.ig.psiutils.SwitchUtils;
+import one.util.streamex.StreamEx;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -837,7 +838,20 @@ public final class RedundantCastUtil {
             }
           }
           if (opType != null) {
-            addIfNarrowing(cast, opType, null);
+            PsiCodeBlock body = switchBlock.getBody();
+            boolean hasInconvertibleLabel = false;
+            if (body != null) {
+              hasInconvertibleLabel = StreamEx.of(body.getStatements()).select(PsiSwitchLabelStatementBase.class)
+                .map(PsiSwitchLabelStatementBase::getCaseLabelElementList)
+                .nonNull().flatArray(PsiCaseLabelElementList::getElements)
+                .select(PsiExpression.class)
+                .map(PsiExpression::getType)
+                .nonNull()
+                .anyMatch(t -> !t.isConvertibleFrom(opType));
+            }
+            if (!hasInconvertibleLabel) {
+              addIfNarrowing(cast, opType, null);
+            }
           }
         }
       }
diff --git a/java/java-tests/testData/inspection/redundantCast/SwitchUnboxing.java b/java/java-tests/testData/inspection/redundantCast/SwitchUnboxing.java
new file mode 100644
index 000000000000..eeead314cfa9
--- /dev/null
+++ b/java/java-tests/testData/inspection/redundantCast/SwitchUnboxing.java
@@ -0,0 +1,10 @@
+class X {
+  void test() {
+    Integer integer = (int) 'a';
+
+    switch ((int) integer) {
+      case 'a':
+      default:
+    }
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInspection/RedundantCastInspectionTest.java b/java/java-tests/testSrc/com/intellij/java/codeInspection/RedundantCastInspectionTest.java
index 959bc024b2a4..4036396f4e99 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInspection/RedundantCastInspectionTest.java
+++ b/java/java-tests/testSrc/com/intellij/java/codeInspection/RedundantCastInspectionTest.java
@@ -110,6 +110,8 @@ public class RedundantCastInspectionTest extends LightJavaCodeInsightFixtureTest
   public void testInConditionalPreserveResolve() { doTest(); }
 
   public void testArrayAccess() { doTest(); }
+  
+  public void testSwitchUnboxing() { doTest(); }
 
   public void testPackagePrivate() {
     myFixture.addClass("package a; public class A {void foo() {}}");