Merge branch 'master' of https://github.com/php-etl/fast-map

# Conflicts:
#	src/Mapping/Composite/ArrayMapper.php

Author: sylvainraye

src/Mapping/Composite/ArrayMapper.php

@@ -43,13 +43,25 @@ public function __invoke($input, $output, PropertyPathInterface $outputPath)
 
     public function compile(Node\Expr $outputNode): array
     {
-        $output = [];
-        foreach ($this->fields as $field) {
-            if ($field instanceof CompilableInterface) {
-                $output = array_merge($output, $field->compile($outputNode));
+        return array_merge(
+            ...$this->compileMappers($outputNode)
+        );
+    }
+
+    private function compileMappers(Node\Expr $outputNode): iterable
+    {
+        foreach ($this->fields as $mapper) {
+            if (!$mapper instanceof Contracts\CompilableInterface) {
+                throw new \RuntimeException(strtr(
+                    'Expected a %expected%, but got an object of type %actual%.',
+                    [
+                        '%expected%' => Contracts\CompilableInterface::class,
+                        '%actual%' => get_class($mapper),
+                    ]
+                ));
             }
-        }
 
-        return $output;
+            yield $mapper->compile($outputNode);
+        }
     }
 }