Improve reduce() signature to exclude null from return type when non-null initial value is passed

phpstan-baseline.neon

@@ -0,0 +1,12 @@
+parameters:
+	ignoreErrors:
+		-
+			message: "#^Parameter \\#1 \\$ of callable callable\\(TResult, TValue\\)\\: TResult expects TResult, TResult\\|null given\\.$#"
+			count: 1
+			path: src/iterable-functions.php
+
+		-
+			message: "#^Function BenTools\\\\IterableFunctions\\\\iterable_reduce\\(\\) should return TResult but returns TResult\\|null\\.$#"
+			count: 1
+			path: src/iterable-functions.php
+

phpstan.neon.dist

@@ -10,3 +10,6 @@ parameters:
         - '~Method BenTools\\IterableFunctions\\IterableObject::map\(\) should return BenTools\\IterableFunctions\\IterableObject<TKey, TResult> but returns BenTools\\IterableFunctions\\IterableObject<int\|string, TResult>~'
 
         - '~Function BenTools\\IterableFunctions\\iterable_map\(\) should return iterable<TKey, TResult> but returns array<TResult>\|BenTools\\IterableFunctions\\IterableObject<TKey, TResult>~'
+
+includes:
+    - phpstan-baseline.neon

src/iterable-functions.php

@@ -95,10 +95,10 @@ function iterable_filter(iterable $iterable, ?callable $filter = null): iterable
  * Reduces an iterable.
  *
  * @param iterable<TValue> $iterable
- * @param callable(TResult|null, TValue):TResult $reduce
- * @param TResult|null $initial
+ * @param TResult $initial
+ * @param callable(TResult, TValue):TResult $reduce
  *
- * @return TResult|null
+ * @return TResult
  *
  * @template TValue
  * @template TResult