From ce8c5cda4a2fbcf4e96f180842e4cd2e4e5173ed Mon Sep 17 00:00:00 2001
From: Bas Leijdekkers <basleijdekkers@gmail.com>
Date: Wed, 29 Jun 2022 11:44:16 +0200
Subject: [PATCH] unused declaration: report Kotlin unused main function
 parameters

GitOrigin-RevId: 0c40f76d3db6539c2217e1aa7967f0e90689f083
---
 .../deadCode/UnusedParametersInspection.java         | 12 ++++++++----
 .../jvm/deadCode/mainParameter/expected.xml          |  9 +++++++++
 .../jvm/deadCode/mainParameter/src/Main.kt           |  3 +++
 .../tests/kotlin/UnusedDeclarationKtTest20.java      |  6 ++++++
 4 files changed, 26 insertions(+), 4 deletions(-)
 create mode 100644 java/java-tests/testData/inspection/jvm/deadCode/mainParameter/expected.xml
 create mode 100644 java/java-tests/testData/inspection/jvm/deadCode/mainParameter/src/Main.kt

diff --git a/java/java-impl/src/com/intellij/codeInspection/deadCode/UnusedParametersInspection.java b/java/java-impl/src/com/intellij/codeInspection/deadCode/UnusedParametersInspection.java
index def102ca12dc..2c7d990f6d41 100644
--- a/java/java-impl/src/com/intellij/codeInspection/deadCode/UnusedParametersInspection.java
+++ b/java/java-impl/src/com/intellij/codeInspection/deadCode/UnusedParametersInspection.java
@@ -25,6 +25,7 @@ import org.jetbrains.uast.UParameter;
 
 import javax.swing.*;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.stream.Stream;
 
@@ -45,13 +46,15 @@ class UnusedParametersInspection extends GlobalJavaBatchInspectionTool {
     if (aClass != null && ((refMethod.isAbstract() || aClass.isInterface()) && refMethod.getDerivedReferences().isEmpty())) {
       return null;
     }
-    if (refMethod.isAppMain()) return null;
     List<RefParameter> unusedParameters = getUnusedParameters(refMethod);
     if (unusedParameters.isEmpty()) return null;
-    if (refMethod.isEntry()) return null;
     UDeclaration uMethod = refMethod.getUastElement();
     if (uMethod == null) return null;
     PsiElement element = uMethod.getJavaPsi();
+    if (refMethod.isAppMain()) {
+      if (element == null || !element.getLanguage().isKindOf("kotlin")) return null;
+    }
+    else if (refMethod.isEntry()) return null;
     if (element != null && EntryPointsManager.getInstance(manager.getProject()).isEntryPoint(element)) return null;
 
     List<ProblemDescriptor> result = new ArrayList<>();
@@ -151,10 +154,11 @@ class UnusedParametersInspection extends GlobalJavaBatchInspectionTool {
   }
 
   @NotNull
-  private static ArrayList<RefParameter> getUnusedParameters(@NotNull RefMethod refMethod) {
+  private static List<RefParameter> getUnusedParameters(@NotNull RefMethod refMethod) {
+    RefParameter[] methodParameters = refMethod.getParameters();
+    if (methodParameters.length == 0) return Collections.emptyList();
     boolean checkDeep = !refMethod.isStatic() && !refMethod.isConstructor();
     ArrayList<RefParameter> res = new ArrayList<>();
-    RefParameter[] methodParameters = refMethod.getParameters();
     RefParameter[] result = methodParameters.clone();
 
     clearUsedParameters(refMethod, result, checkDeep);
diff --git a/java/java-tests/testData/inspection/jvm/deadCode/mainParameter/expected.xml b/java/java-tests/testData/inspection/jvm/deadCode/mainParameter/expected.xml
new file mode 100644
index 000000000000..a3955cce2c1b
--- /dev/null
+++ b/java/java-tests/testData/inspection/jvm/deadCode/mainParameter/expected.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<problems>
+  <problem>
+    <file>Main.kt</file>
+    <line>1</line>
+    <problem_class id="unused" severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Unused declaration</problem_class>
+    <description>Parameter &lt;code&gt;args&lt;/code&gt; is not used</description>
+  </problem>
+</problems>
\ No newline at end of file
diff --git a/java/java-tests/testData/inspection/jvm/deadCode/mainParameter/src/Main.kt b/java/java-tests/testData/inspection/jvm/deadCode/mainParameter/src/Main.kt
new file mode 100644
index 000000000000..6380b1ee5f19
--- /dev/null
+++ b/java/java-tests/testData/inspection/jvm/deadCode/mainParameter/src/Main.kt
@@ -0,0 +1,3 @@
+fun main(args: Array<String>) {
+  println("Hello world!")
+}
\ No newline at end of file
diff --git a/jvm/jvm-analysis-kotlin-tests/testSrc/com/intellij/codeInspection/tests/kotlin/UnusedDeclarationKtTest20.java b/jvm/jvm-analysis-kotlin-tests/testSrc/com/intellij/codeInspection/tests/kotlin/UnusedDeclarationKtTest20.java
index 2959569b0122..ab4a4068d85a 100644
--- a/jvm/jvm-analysis-kotlin-tests/testSrc/com/intellij/codeInspection/tests/kotlin/UnusedDeclarationKtTest20.java
+++ b/jvm/jvm-analysis-kotlin-tests/testSrc/com/intellij/codeInspection/tests/kotlin/UnusedDeclarationKtTest20.java
@@ -69,6 +69,12 @@ public class UnusedDeclarationKtTest20 extends AbstractUnusedDeclarationTest {
     doTest("deadCode/" + getTestName(true), myToolWrapper);
   }
 
+  public void testMainParameter() {
+    myTool.getSharedLocalInspectionTool().PARAMETER = true;
+    myTool.getSharedLocalInspectionTool().LOCAL_VARIABLE = false;
+    doTest("deadCode/" + getTestName(true), myToolWrapper);
+  }
+
   public void testStaticMethods() {
     doTest();
   }