Issue #3144: fixed NPE in FinalLocalVariable for lambda in field (#3146)

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

@@ -562,7 +562,7 @@ public class FinalLocalVariableCheck extends AbstractCheck {
     }
 
     /**
-     * Find the Class, Constructor, Enum or Method in which it is defined.
+     * Find the Class, Constructor, Enum, Method, or Field in which it is defined.
      * @param ast Variable for which we want to find the scope in which it is defined
      * @return ast The Class or Constructor or Method in which it is defined.
      */
@@ -571,7 +571,9 @@ public class FinalLocalVariableCheck extends AbstractCheck {
         while (astTraverse.getType() != TokenTypes.METHOD_DEF
                 && astTraverse.getType() != TokenTypes.CLASS_DEF
                 && astTraverse.getType() != TokenTypes.ENUM_DEF
-                && astTraverse.getType() != TokenTypes.CTOR_DEF) {
+                && astTraverse.getType() != TokenTypes.CTOR_DEF
+                && (astTraverse.getType() != TokenTypes.VARIABLE_DEF
+                        || !ScopeUtils.isClassFieldDef(astTraverse))) {
             astTraverse = astTraverse.getParent();
         }
         return astTraverse;

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

@@ -160,7 +160,9 @@ public class FinalLocalVariableCheckTest
         final DefaultConfiguration checkConfig =
             createCheckConfig(FinalLocalVariableCheck.class);
         checkConfig.addAttribute("tokens", "PARAMETER_DEF,VARIABLE_DEF");
-        final String[] expected = CommonUtils.EMPTY_STRING_ARRAY;
+        final String[] expected = {
+            "32:16: " + "Variable 'result' should be declared final.",
+        };
         verify(checkConfig, getNonCompilablePath("InputFinalLocalVariableNameLambda.java"),
             expected);
     }

src/test/resources-noncompilable/com/puppycrawl/tools/checkstyle/checks/coding/InputFinalLocalVariableNameLambda.java

@@ -25,3 +25,12 @@ public class InputFinalLocalVariableNameLambda {
                     (t, u) -> t.add(u.getAmount()));
  }
 }
+interface Operation {
+    public Object apply();
+
+    public static final Operation OPERATION = () -> {
+        Object result;
+        result = null;
+        return result;
+    };
+}