Java: inner class accessing local variable or parameter can't be static (IDEA-375602)

(cherry picked from commit 1b16d1388c09d51009b288ede89e73d156364619)

IJ-CR-168593

GitOrigin-RevId: 7ff7cfa95cdc674c5b1d32a572eec0b95bbfb58d

java/java-analysis-impl/src/com/siyeh/ig/memory/InnerClassReferenceVisitor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2017 Dave Griffith, Bas Leijdekkers
+ * Copyright 2003-2025 Dave Griffith, Bas Leijdekkers
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,11 +24,11 @@ import org.jetbrains.annotations.NotNull;
 public class InnerClassReferenceVisitor extends JavaRecursiveElementWalkingVisitor {
 
   private final PsiClass innerClass;
+  private final boolean allowReferencesToLocalVariables;
   private boolean referencesStaticallyAccessible = true;
-  private boolean allowReferencesToLocalVariables = true;
 
   public InnerClassReferenceVisitor(@NotNull PsiClass innerClass) {
-    this.innerClass = innerClass;
+    this(innerClass, false);
   }
 
   public InnerClassReferenceVisitor(@NotNull PsiClass innerClass, boolean allowReferencesToLocalVariables) {
@@ -51,8 +51,8 @@ public class InnerClassReferenceVisitor extends JavaRecursiveElementWalkingVisit
     if (PsiTreeUtil.isAncestor(innerClass, aClass, false) || aClass.hasModifierProperty(PsiModifier.STATIC)) {
       return true;
     }
-    if (aClass instanceof PsiTypeParameter) {
+    if (aClass instanceof PsiTypeParameter parameter) {
-      PsiTypeParameterListOwner owner = ((PsiTypeParameter)aClass).getOwner();
+      PsiTypeParameterListOwner owner = parameter.getOwner();
       return owner != null && PsiTreeUtil.isAncestor(innerClass, owner, false);
     }
     final PsiClass containingClass = aClass.getContainingClass();
@@ -98,7 +98,7 @@ public class InnerClassReferenceVisitor extends JavaRecursiveElementWalkingVisit
     }
     final PsiElement target = expression.resolve();
     if (target == null) {
-      referencesStaticallyAccessible = false; // TODO(bartekpacia): We probably should introduce the 3rd "unknown" state to signal this
+      referencesStaticallyAccessible = false;
       return;
     }
     if (target instanceof PsiLocalVariable || target instanceof PsiParameter) {
@@ -128,7 +128,7 @@ public class InnerClassReferenceVisitor extends JavaRecursiveElementWalkingVisit
       }
       referencesStaticallyAccessible = false;
     }
-    else if (target instanceof PsiClass && !isClassStaticallyAccessible((PsiClass)target)) {
+    else if (target instanceof PsiClass aClass && !isClassStaticallyAccessible(aClass)) {
       referencesStaticallyAccessible = false;
     }
   }
@@ -144,10 +144,7 @@ public class InnerClassReferenceVisitor extends JavaRecursiveElementWalkingVisit
       return;
     }
     final PsiElement target = classReference.resolve();
-    if (!(target instanceof PsiClass)) {
+    if (target instanceof PsiClass aClass && !isClassStaticallyAccessible(aClass)) {
-      return;
-    }
-    if (!isClassStaticallyAccessible((PsiClass)target)) {
       referencesStaticallyAccessible = false;
     }
   }

java/java-impl-inspections/src/com/intellij/codeInspection/classCanBeRecord/ConvertToRecordFix.java

@@ -128,7 +128,7 @@ public final class ConvertToRecordFix implements LocalQuickFix {
    * @see com.siyeh.ig.memory.InnerClassMayBeStaticInspection
    */
   private static boolean containsOuterNonStaticReferences(PsiClass psiClass) {
-    InnerClassReferenceVisitor visitor = new InnerClassReferenceVisitor(psiClass, false);
+    InnerClassReferenceVisitor visitor = new InnerClassReferenceVisitor(psiClass);
     psiClass.accept(visitor);
     return !visitor.canInnerClassBeStatic();
   }

java/java-impl/src/com/siyeh/ig/memory/AnonymousInnerClassMayBeStaticInspection.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2023 Dave Griffith, Bas Leijdekkers
+ * Copyright 2003-2025 Dave Griffith, Bas Leijdekkers
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -78,7 +78,7 @@ public final class AnonymousInnerClassMayBeStaticInspection extends BaseInspecti
         // strictly speaking can be named static inner class but not when part of the current containing class
         return;
       }
-      final InnerClassReferenceVisitor visitor = new InnerClassReferenceVisitor(anonymousClass);
+      final InnerClassReferenceVisitor visitor = new InnerClassReferenceVisitor(anonymousClass, true);
       anonymousClass.accept(visitor);
       if (!visitor.canInnerClassBeStatic()) {
         return;
@@ -106,7 +106,7 @@ public final class AnonymousInnerClassMayBeStaticInspection extends BaseInspecti
           return;
         }
         final PsiElement target = reference.resolve();
-        if (!(target instanceof PsiClass) || !PsiUtil.isLocalClass((PsiClass)target)) {
+        if (!(target instanceof PsiClass aClass) || !PsiUtil.isLocalClass(aClass)) {
           return;
         }
         referenceToLocalClass = true;

java/java-tests/testData/ig/com/siyeh/igtest/memory/inner_class_may_be_static/InnerStaticsJDK16.after.java

@@ -26,4 +26,15 @@ class One<A> {
   public static void main(String[] args) {
     One.Two.Three<Void> x;
   }
+}
+class C {
+  void x(int i) {
+    new Object() {
+      class Local { // can't be static
+        int get() {
+          return i;
+        }
+      }
+    };
+  }
 }

java/java-tests/testData/ig/com/siyeh/igtest/memory/inner_class_may_be_static/InnerStaticsJDK16.java

@@ -26,4 +26,15 @@ class One<A> {
   public static void main(String[] args) {
     One<Void>.Two<Void>.Three<Void> x;
   }
+}
+class C {
+  void x(int i) {
+    new Object() {
+      class Local { // can't be static
+        int get() {
+          return i;
+        }
+      }
+    };
+  }
 }

java/java-tests/testSrc/com/siyeh/ig/classlayout/ClassMayBeInterfaceInspectionTest.java

@@ -1,18 +1,4 @@
-/*
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
- * Copyright 2000-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
 package com.siyeh.ig.classlayout;
 
 import com.intellij.codeInspection.InspectionProfileEntry;
@@ -69,6 +55,30 @@ public class ClassMayBeInterfaceInspectionTest extends LightJavaInspectionTestCa
              }""");
   }
 
+  public void testLocalClassAccessingParameter() {
+    doTest("""
+             class Outer {
+               void x(int parameter) {
+                 abstract class Example {
+                   public static final int MY_CONST = 42;
+                   public abstract void foo();
+             
+                   public void g() {
+                     System.out.println(parameter);
+                   }
+                 }
+             
+                 class Inheritor extends Example {
+                   @Override
+                   public void foo() {
+                     System.out.println(MY_CONST);
+                   }
+                 }
+               }
+             }
+             """);
+  }
+
   @Override
   protected InspectionProfileEntry getInspection() {
     final ClassMayBeInterfaceInspection inspection = new ClassMayBeInterfaceInspection();