Draft of "False positive for S1854 Solution"

- https://community.sonarsource.com/t/false-positive-for-s1854-unused-assignments-should-be-removed/114110/10

Author: rombirli

java-checks-test-sources/default/src/main/java/checks/UnusedVariablesFPCheck.java

@@ -0,0 +1,119 @@
+package com;
+
+
+public class UnusedVariablesFPCheck {
+  public class DeobfuscatedUpdateManager {
+//    private interface DataContainer {
+//      Iterable<ItemElement> getItems();
+//    }
+//
+//    private interface ModelObject {
+//      void performAction();
+//    }
+//
+//    private interface ItemElement {
+//      ModelObject getDataModel();
+//    }
+//
+//    private static class SystemConfig {
+//      static ConfigMode getMode() {
+//        return ConfigMode.ENABLED;
+//      }
+//    }
+//
+//    private enum ConfigMode {
+//      ENABLED,
+//      DISABLED
+//    }
+//
+//    static class A {
+//      interface GenericCallback<T> { }
+//    }
+
+    /**
+     * Deobfuscated names with AI from :
+     * ```java
+     * package com;
+     * <p>
+     * public class BCid51 {
+     * void HJid232(EJid229 YHid199, Yid24.RIid217<MBid37> QJid241) {
+     * for (XFid148 RJid242 : YHid199.WIid222()) {
+     * int DHid178;
+     * if (Fid5.BGid151() == CGid152.DGid153) {
+     * MBid37 IHid183 = RJid242.OFid139();
+     * IHid183.AGid150();
+     * }
+     * }
+     * }
+     * }
+     * ```
+     */
+    void processUpdates(
+      DataContainer container
+      // REMARK : the issue arises from the A.GenericCallback<ModelObject> callback that is not even used (indirect type resolution problem)
+      , A.GenericCallback<X> callback
+    ) {
+      for (ItemElement element : container.getItems()) {
+        if (SystemConfig.getMode() == ConfigMode.ENABLED) {
+          ModelObject dataModel = element.getDataModel();
+          dataModel.performAction();
+        }
+      }
+    }
+
+  }
+
+  static class StringConcatenation {
+//    private class AClass {
+//      private class BClass<T> {
+//        public T b;
+//      }
+//    }
+
+    public String doSomething(AClass.BClass<String> instance) {
+      String c = "Hi"; // Rule S1854
+      return instance.b + c;
+    }
+  }
+
+  static class EnhancedSwitch {
+//    private enum DocumentStatus {
+//      DOC01,
+//      DOC02
+//    }
+//
+//    private interface Document {
+//      void setStatus(DocumentStatus status);
+//    }
+//
+//    private interface Event {
+//    }
+//
+//    private class SimpleStatusChangedEvent implements Event {
+//    }
+//
+//    private class NeedClientRecheckEvent implements Event {
+//    }
+//    private interface DocumentRepository {
+//      void save(Document document);
+//    }
+
+    void ko(Event event, Document document, DocumentRepository documentRepository) {
+      final DocumentStatus status = switch (event) {
+        case SimpleStatusChangedEvent ignored -> DocumentStatus.DOC01;
+        case NeedClientRecheckEvent ignored -> DocumentStatus.DOC02;
+      };
+      document.setStatus(status);
+      // ...
+      documentRepository.save(document);
+    }
+
+  }
+
+  class Obvious {
+//    void obvious() {
+//      int i = 0; // doesn't raise issue
+//      i = 1; // raises issue
+//    }
+  }
+}

java-checks/src/test/java/org/sonar/java/checks/DeadStoreCheckTest.java

@@ -51,6 +51,15 @@ void test_non_compiling() {
       .verifyIssues();
   }
 
+  @Test
+  void test_fp() {
+    CheckVerifier.newVerifier()
+      .onFile(TestUtils.mainCodeSourcesPath("checks/UnusedVariablesFPCheck.java"))
+      .withJavaVersion(14)
+      .withCheck(new DeadStoreCheck())
+      .verifyNoIssues();
+  }
+
   private static class EraseSymbols extends BaseTreeVisitor {
 
     @Override

java-frontend/src/main/java/org/sonar/java/model/Symbols.java

@@ -99,7 +99,7 @@ public final boolean isTypeSymbol() {
     }
 
     @Override
-    public final boolean isMethodSymbol() {
+    public boolean isMethodSymbol() {
       return false;
     }
 
@@ -340,6 +340,9 @@ public boolean isVarArgsMethod() {
     public boolean isNativeMethod() {
       return false;
     }
+
+    @Override
+    public boolean isMethodSymbol() { return true; }
   }
 
   public static final class UnknownType implements Type {