bug #7 Fix method signatures for legacy compatibility (Frans Weerts)

This PR was squashed before being merged into the main branch.

Discussion
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Fix method signatures for legacy compatibility

Fixes #5

Commits
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090e89d Fix method signatures for legacy compatibility

src/DynamicFormBuilder.php

@@ -191,7 +191,10 @@ public function count(): int
         return $this->builder->count();
     }
 
-    public function add(string|FormBuilderInterface $child, string $type = null, array $options = []): static
+    /**
+     * @param string|FormBuilderInterface $child
+     */
+    public function add($child, string $type = null, array $options = []): static
     {
         $this->builder->add($child, $type, $options);
 
@@ -286,7 +289,7 @@ public function setAttributes(array $attributes): static
         return $this;
     }
 
-    public function setDataMapper(?DataMapperInterface $dataMapper): static
+    public function setDataMapper(DataMapperInterface $dataMapper = null): static
     {
         $this->builder->setDataMapper($dataMapper);
 
@@ -335,7 +338,10 @@ public function setMethod(string $method): static
         return $this;
     }
 
-    public function setPropertyPath(null|string|PropertyPathInterface $propertyPath): static
+    /**
+     * @param string|PropertyPathInterface|null $propertyPath
+     */
+    public function setPropertyPath($propertyPath): static
     {
         $this->builder->setPropertyPath($propertyPath);