Java: fix type inference for switch expressions (IDEA-311533)

GitOrigin-RevId: 153bc92d71655760c10d5b7e42d3600310845f42

java/java-psi-api/src/com/intellij/psi/impl/source/resolve/graphInference/PsiPolyExpressionUtil.java

@@ -1,4 +1,4 @@
-// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package com.intellij.psi.impl.source.resolve.graphInference;
 
 import com.intellij.pom.java.JavaFeature;
@@ -210,6 +210,7 @@ public final class PsiPolyExpressionUtil {
           }
         }
       }
+      return switchKind;
     }
     return null;
   }

java/java-tests/testData/psi/resolve/method/SwitchExpressionType.java

@@ -0,0 +1,8 @@
+class SwitchExpressionType {
+  public static void main(String[] args) {
+    System.out.<caret>print(switch (args.length) {
+      case 1 -> 1;
+      default -> 2;
+    });
+  }
+}

java/java-tests/testSrc/com/intellij/java/psi/resolve/ResolveMethodTest.java

@@ -1,8 +1,10 @@
-// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package com.intellij.java.psi.resolve;
 
+import com.intellij.pom.java.LanguageLevel;
 import com.intellij.psi.*;
 import com.intellij.psi.infos.MethodCandidateInfo;
+import com.intellij.testFramework.IdeaTestUtil;
 import com.intellij.testFramework.LightProjectDescriptor;
 import com.intellij.testFramework.LightResolveTestCase;
 import org.jetbrains.annotations.NotNull;
@@ -259,6 +261,13 @@ public class ResolveMethodTest extends LightResolveTestCase {
     assertEquals("PublicCloneable", method.getContainingClass().getName());
   }
 
+  public void testSwitchExpressionType() {
+    IdeaTestUtil.withLevel(getModule(), LanguageLevel.JDK_1_8, () -> {
+      PsiMethod target = (PsiMethod)resolve();
+      assertEquals(PsiTypes.intType(), target.getParameterList().getParameters()[0].getType());
+    });
+  }
+
   public void testMultipleJavadocReference() {
     PsiJavaReference ref = (PsiJavaReference)findReferenceAtCaret("method/" + getTestName(false) + ".java");
     assertSize(3, ref.multiResolve(false));