Fixed incomplete return type signature on insertGetId method. Updated Model class and added test.

src/Illuminate/Database/Eloquent/Model.php

@@ -1356,9 +1356,12 @@ protected function performInsert(Builder $query)
      */
     protected function insertAndSetId(Builder $query, $attributes)
     {
+        /** @var int|false $id */
         $id = $query->insertGetId($attributes, $keyName = $this->getKeyName());
 
-        $this->setAttribute($keyName, $id);
+        if ($id !== false) {
+            $this->setAttribute($keyName, $id);
+        }
     }
 
     /**

src/Illuminate/Database/Query/Builder.php

@@ -3786,7 +3786,7 @@ public function insertOrIgnore(array $values)
      *
      * @param  array  $values
      * @param  string|null  $sequence
-     * @return int
+     * @return false|int
      */
     public function insertGetId(array $values, $sequence = null)
     {

src/Illuminate/Database/Query/Processors/MySqlProcessor.php

@@ -28,7 +28,7 @@ public function processColumnListing($results)
      * @param  string  $sql
      * @param  array  $values
      * @param  string|null  $sequence
-     * @return int
+     * @return false|int
      */
     public function processInsertGetId(Builder $query, $sql, $values, $sequence = null)
     {

src/Illuminate/Database/Query/Processors/Processor.php

@@ -25,7 +25,7 @@ public function processSelect(Builder $query, $results)
      * @param  string  $sql
      * @param  array  $values
      * @param  string|null  $sequence
-     * @return int
+     * @return false|int
      */
     public function processInsertGetId(Builder $query, $sql, $values, $sequence = null)
     {

src/Illuminate/Database/Query/Processors/SqlServerProcessor.php

@@ -15,7 +15,7 @@ class SqlServerProcessor extends Processor
      * @param  string  $sql
      * @param  array  $values
      * @param  string|null  $sequence
-     * @return int
+     * @return false|int
      */
     public function processInsertGetId(Builder $query, $sql, $values, $sequence = null)
     {

tests/Database/DatabaseProcessorTest.php

@@ -29,6 +29,28 @@ public function testInsertGetIdProcessing()
         $result = $processor->processInsertGetId($builder, 'sql', ['foo'], 'id');
         $this->assertSame(1, $result);
     }
+
+    public function testInsertAndSetIdHandlesFalseGracefully()
+    {
+        // Mock the Builder to return false for insertGetId
+        $builderMock = $this->createMock(\Illuminate\Database\Eloquent\Builder::class);
+        $builderMock->method('insertGetId')->willReturn(false);
+
+        // Mock the Model
+        $modelMock = $this->getMockBuilder(\Illuminate\Database\Eloquent\Model::class)
+            ->onlyMethods(['getKeyName', 'setAttribute'])
+            ->getMock();
+
+        $modelMock->method('getKeyName')->willReturn('id');
+
+        // Expect setAttribute NOT to be called since ID should not be set
+        $modelMock->expects($this->never())->method('setAttribute');
+
+        // Call the protected method using reflection
+        $reflection = new \ReflectionMethod($modelMock, 'insertAndSetId');
+        $reflection->setAccessible(true);
+        $reflection->invoke($modelMock, $builderMock, ['name' => 'Test']);
+    }
 }
 
 class ProcessorTestPDOStub extends PDO