fix(stubs): narrow Collection::sum() no-arg return type by TValue #678

Collection<_, int>::sum() now returns int instead of int|float,
matching Psalm's array_sum behavior for typed arrays.

Author: alies-dev

stubs/common/Support/Collection.stubphp

@@ -203,10 +203,18 @@ class Collection implements ArrayAccess, CanBeEscapedWhenCastToString, Enumerabl
      * At runtime, the accumulator starts at 0 and uses the + operator,
      * so the result is always int|float (non-numeric values throw TypeError).
      *
+     * When called without arguments, the return type narrows based on TValue:
+     * - Collection<_, int>::sum() → int (matches array_sum behavior for int arrays)
+     * - Collection<_, float>::sum() → float
+     * - Otherwise → int|float
+     *
      * @template TCallbackReturn of int|float
      *
      * @param  (callable(TValue, TKey): TCallbackReturn)|string|null  $callback
-     * @return ($callback is string|null ? int|float : TCallbackReturn)
+     * @return ($callback is null
+     *  ? (TValue is int ? int : (TValue is float ? float : int|float))
+     *  : ($callback is string ? int|float : TCallbackReturn)
+     * )
      */
     public function sum($callback = null) {}
 }

stubs/common/Support/Enumerable.stubphp

@@ -17,10 +17,15 @@ interface Enumerable extends \Illuminate\Contracts\Support\Arrayable, \Countable
      * At runtime, the accumulator starts at 0 and uses the + operator,
      * so the result is always int|float (non-numeric values throw TypeError).
      *
+     * When called without arguments, the return type narrows based on TValue:
+     * - Collection<_, int>::sum() → int (matches array_sum behavior for int arrays)
+     * - Collection<_, float>::sum() → float
+     * - Otherwise → int|float
+     *
      * @template TCallbackReturn of int|float
      *
      * @param  (callable(TValue, TKey): TCallbackReturn)|string|null  $callback
-     * @return ($callback is string|null ? int|float : TCallbackReturn)
+     * @return ($callback is null ? (TValue is int ? int : (TValue is float ? float : int|float)) : ($callback is string ? int|float : TCallbackReturn))
      */
     public function sum($callback = null);
 }

tests/Type/tests/CollectionMethodsTest.phpt

@@ -211,11 +211,35 @@ final class CollectionTypes
     }
 
     /** @see https://github.com/psalm/psalm-plugin-laravel/issues/678 */
-    public function sumWithoutArguments(): int|float
+    public function sumWithoutArguments(): int
     {
         /** @var Collection<int, int> */
         $numbers = new Collection();
 
+        /** @psalm-check-type-exact $sum = int */
+        $sum = $numbers->sum();
+
+        return $sum;
+    }
+
+    /** @see https://github.com/psalm/psalm-plugin-laravel/issues/678 */
+    public function sumWithoutArgumentsFloat(): float
+    {
+        /** @var Collection<int, float> */
+        $numbers = new Collection();
+
+        /** @psalm-check-type-exact $sum = float */
+        $sum = $numbers->sum();
+
+        return $sum;
+    }
+
+    /** @see https://github.com/psalm/psalm-plugin-laravel/issues/678 */
+    public function sumWithoutArgumentsMixed(): int|float
+    {
+        /** @var Collection<int, int|float> */
+        $numbers = new Collection();
+
         /** @psalm-check-type-exact $sum = float|int */
         $sum = $numbers->sum();