Trigger a deprecation notice when entity fields/associations are overridden

This was brought up in #8348, but seemingly forgotten to be implenented in later versions.

Closes #10289.

Author: mpdude

UPGRADE.md

@@ -1,5 +1,11 @@
 # Upgrade to 2.15
 
+## Deprecated overriding fields or associations not declared in mapped superclasses
+
+As stated in the documentation, fields and associations may only be overridden when being inherited
+from mapped superclasses. Overriding them for parent entity classes now triggers a deprecation notice
+and will be an error in 3.0.
+
 ## Deprecated undeclared entity inheritance
 
 As soon as an entity class inherits from another entity class, inheritance has to 

lib/Doctrine/ORM/Mapping/ClassMetadataInfo.php

@@ -2693,10 +2693,16 @@ public function setAttributeOverride($fieldName, array $overrideMapping)
 
         $mapping = $this->fieldMappings[$fieldName];
 
-        //if (isset($mapping['inherited'])) {
-            // TODO: Enable this exception in 2.8
+        if (isset($mapping['inherited'])) {
+            Deprecation::trigger(
+                'doctrine/orm',
+                'https://github.com/doctrine/orm/pull/10470',
+                'Overrides are only allowed for fields or associations declared in mapped superclasses or traits, which is not the case for %s::%s. This is a misconfiguration and will be an error in Doctrine ORM 3.0.',
+                $this->name,
+                $fieldName
+            );
             //throw MappingException::illegalOverrideOfInheritedProperty($this->name, $fieldName);
-        //}
+        }
 
         if (isset($mapping['id'])) {
             $overrideMapping['id'] = $mapping['id'];

lib/Doctrine/ORM/Mapping/MappingException.php

@@ -908,8 +908,7 @@ public static function illegalOverrideOfInheritedProperty($className, $propertyN
     {
         return new self(
             sprintf(
-                'Override for %s::%s is only allowed for attributes/associations ' .
-                'declared on a mapped superclass or a trait.',
+                'Overrides are only allowed for fields or associations declared in mapped superclasses or traits, which is not the case for %s::%s.',
                 $className,
                 $propertyName
             )

tests/Doctrine/Tests/ORM/Mapping/BasicInheritanceMappingTest.php

@@ -25,6 +25,7 @@
 use Doctrine\ORM\Mapping\Table;
 use Doctrine\ORM\Mapping\UniqueConstraint;
 use Doctrine\Persistence\Mapping\RuntimeReflectionService;
+use Doctrine\Tests\Models\Company\CompanyFixContract;
 use Doctrine\Tests\Models\DDC869\DDC869ChequePayment;
 use Doctrine\Tests\Models\DDC869\DDC869CreditCardPayment;
 use Doctrine\Tests\Models\DDC869\DDC869Payment;
@@ -250,6 +251,15 @@ public function invalidHierarchyDeclarationClasses(): Generator
         yield 'complex example (Entity Root -> Mapped Superclass -> transient class -> Entity)'
             => [InvalidComplexRoot::class, InvalidComplexEntity::class];
     }
+
+    /** @group DDC-964 */
+    public function testInvalidOverrideFieldInheritedFromEntity(): void
+    {
+        $this->expectDeprecationWithIdentifier('https://github.com/doctrine/orm/pull/10470');
+
+        $cm = $this->cmf->getMetadataFor(CompanyFixContract::class);
+        $cm->setAttributeOverride('completed', ['name' => 'other_column_name']);
+    }
 }
 
 class TransientBaseClass