Fix function declaration

.gitignore

@@ -1,13 +1,21 @@
-nbproject
-docs/api/phpdoc-cache-*
-docs/coverage
+# composer generated files
 /vendor/
+composer.lock
+
+# -- Temp folder
 coverage.xml
+docs/api/phpdoc-cache-*
+docs/coverage
+yarn.lock
+test-report.xml
+
+# -- IDE specific path / files
+nbproject
 .settings
 .buildpath
 .project
-composer.lock
-test-report.xml
-yarn.lock
+.phpunit.result.cache
+.DS_Store
+.reports
 *.iml
-.idea
+.idea

src/phpstream/Stream.php

@@ -236,7 +236,7 @@ public abstract function max(callable|Comparator $cmp = null): Optional;
 	 *
 	 * @return mixed The reduced value of the stream.
 	 */
-	public abstract function reduce(callable|BinaryFunction $reducer, $initialValue = null): mixed;
+	public abstract function reduce(callable|BinaryFunction $reducer, mixed $initialValue = null): mixed;
 
 	/**
 	 * Collect data according given Stream collector.

src/phpstream/impl/GeneratorStream.php

@@ -169,7 +169,7 @@ public function max(callable|Comparator $cmp = null): Optional {
 		return $collector->collect($this->iterable);
 	}
 
-	public function reduce(callable|BinaryFunction $reducer, $initialValue = null): mixed {
+	public function reduce(callable|BinaryFunction $reducer, mixed $initialValue = null): mixed {
 		$iterable = $this->iterable;
 		$fn = $reducer instanceof BinaryFunction
 				? function ($carry, $item) use ($reducer) {