Issue #11920: fix false positive UnusedLocalVariableCheck

src/main/java/com/puppycrawl/tools/checkstyle/checks/coding/UnusedLocalVariableCheck.java

@@ -368,8 +368,11 @@ private static void visitIdentToken(DetailAST identAst, Deque<VariableDesc> vari
                 && parent.getFirstChild() != identAst;
         final boolean isConstructorReference = parent.getType() == TokenTypes.METHOD_REF
                 && parent.getLastChild().getType() == TokenTypes.LITERAL_NEW;
+        final boolean isNestedClassInitialization =
+                TokenUtil.isOfType(identAst.getNextSibling(), TokenTypes.LITERAL_NEW)
+                && parent.getType() == TokenTypes.DOT;
 
-        if (!isMethodReferenceMethodName
+        if (isNestedClassInitialization || !isMethodReferenceMethodName
                 && !isConstructorReference
                 && !TokenUtil.isOfType(parent, UNACCEPTABLE_PARENT_OF_IDENT)) {
             checkIdentifierAst(identAst, variablesStack);

src/test/java/com/puppycrawl/tools/checkstyle/checks/coding/UnusedLocalVariableCheckTest.java

@@ -227,6 +227,20 @@ public void testUnusedLocalVarNestedClasses2() throws Exception {
                 expected);
     }
 
+    @Test
+    public void testUnusedLocalVarNestedClasses3() throws Exception {
+        final String[] expected = {
+            "36:17: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "p2"),
+            "54:13: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "o"),
+            "93:13: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "b"),
+            "95:13: " + getCheckMessage(MSG_UNUSED_LOCAL_VARIABLE, "a"),
+        };
+
+        verifyWithInlineConfigParser(
+                getPath("InputUnusedLocalVariableNestedClasses3.java"),
+                expected);
+    }
+
     @Test
     public void testUnusedLocalVarEnum() throws Exception {
         final String[] expected = {

src/test/resources/com/puppycrawl/tools/checkstyle/checks/coding/unusedlocalvariable/InputUnusedLocalVariableNestedClasses3.java

@@ -0,0 +1,100 @@
+/*
+UnusedLocalVariable
+
+
+*/
+
+package com.puppycrawl.tools.checkstyle.checks.coding.unusedlocalvariable;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Target;
+
+public class InputUnusedLocalVariableNestedClasses3 {
+    void method() {
+        final OuterClass outerClass = new OuterClass(); // ok
+        final OuterClass.InnerClass innerClass = outerClass.new InnerClass();
+        System.out.println(innerClass);
+    }
+
+    class OuterClass {
+        class InnerClass {
+            InnerClass() { }
+        }
+    }
+
+
+}
+
+class Outer {
+    public class Inner { }
+}
+
+class Test {
+    void m() {
+        @A Outer p1 = new @A Outer(); // ok
+        // violation below 'Unused local variable 'p2'.'
+        @A Outer.@B Inner p2 = p1.new @B Inner();
+    }
+
+    @Target({ElementType.TYPE_USE, ElementType.TYPE_PARAMETER})
+    @interface A { }
+
+    @Target({ElementType.TYPE_USE, ElementType.TYPE_PARAMETER})
+    @interface B { }
+}
+
+class H006_ComplexConstructors<T> {
+    public <V> H006_ComplexConstructors(T t, V v) { }
+
+    class Inner3 {
+        Inner3(int x) {
+            H006_ComplexConstructors<Integer> instance = // ok
+                    new <String>H006_ComplexConstructors<Integer>(0, "");
+            // violation below 'Unused local variable 'o'.'
+            Object o = instance.new Inner3(5).new <String>InnerInner3("hey");
+        }
+
+        class InnerInner3 {
+            <D> InnerInner3(D in) { }
+        }
+    }
+}
+
+class NullQualifiedNew2 {
+    class Inner {
+        Inner(int i) {}
+    }
+
+    public static void main(String[] args) {
+        int i = 1;
+        a: try {
+            NullQualifiedNew2 c = null;
+            c.new Inner(i++) {};
+        } catch (NullPointerException e) {
+            break a;
+        }
+        if (i != 1) throw new Error("i = " + i);
+    }
+}
+
+class T7090499<E> {
+
+    static class B<X> { }
+
+    class A<X> {
+        class X { }
+
+        class Z<Y> { }
+    }
+
+    T7090499 t = new T7090499() {
+        void test(Object arg1, B arg2) {
+            // violation below 'Unused local variable 'b'.'
+            boolean b = arg1 instanceof A;
+            // violation below 'Unused local variable 'a'.'
+            Object a = (A) arg1;
+            A a2 = new A() { };
+            a2.new Z() { };
+        }
+    };
+}