[java-intentions] ConvertSwitchToIf: don't add explicit null check if the selector expression is not null

IDEA-300120

GitOrigin-RevId: d49fa3356b23ec87c8f493fc4cdacb0655e4b600

java/java-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/ConvertSwitchToIfIntention.java

@@ -2,9 +2,11 @@
 package com.intellij.codeInsight.daemon.impl.quickfix;
 
 import com.intellij.codeInsight.BlockUtils;
+import com.intellij.codeInsight.Nullability;
 import com.intellij.codeInsight.daemon.impl.actions.IntentionActionWithFixAllOption;
 import com.intellij.codeInsight.intention.FileModifier;
 import com.intellij.codeInspection.CommonQuickFixBundle;
+import com.intellij.codeInspection.dataFlow.NullabilityUtil;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.project.Project;
 import com.intellij.pom.java.LanguageLevel;
@@ -116,7 +118,9 @@ public class ConvertSwitchToIfIntention implements IntentionActionWithFixAllOpti
       if (aClass != null) {
         String fqn = aClass.getQualifiedName();
         useEquals = !aClass.isEnum() && (fqn == null || !TypeConversionUtil.isPrimitiveWrapper(fqn));
-        needNullCheck = (fqn == null || !TypeConversionUtil.isPrimitiveWrapper(fqn)) && !hasNullCase(allBranches);
+        Nullability nullability = NullabilityUtil.getExpressionNullability(switchExpression, true);
+        needNullCheck =
+          nullability != Nullability.NOT_NULL && (fqn == null || !TypeConversionUtil.isPrimitiveWrapper(fqn)) && !hasNullCase(allBranches);
       }
     }
 

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/convertSwitchToIf/afterNotNull.java

@@ -0,0 +1,16 @@
+// "Replace 'switch' with 'if'" "true-preview"
+
+import org.jetbrains.annotations.NotNull;
+
+class Test {
+
+  void foo(@NotNull Object o) {
+      if (o instanceof String) {
+          System.out.println("one");
+      } else if (o instanceof Integer) {
+          System.out.println("two");
+      } else {
+          System.out.println("default");
+      }
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/convertSwitchToIf/beforeNotNull.java

@@ -0,0 +1,14 @@
+// "Replace 'switch' with 'if'" "true-preview"
+
+import org.jetbrains.annotations.NotNull;
+
+class Test {
+
+  void foo(@NotNull Object o) {
+    switch<caret> (o) {
+      case String s -> System.out.println("one");
+      case Integer i -> System.out.println("two");
+      case default -> System.out.println("default");
+    }
+  }
+}