Could not infer a return type for array_reduce

[melihovv]

https://psalm.dev/r/57243f56e5

<?php

/**
 * @template TKey as array-key
 * @template TValue as mixed
 */
abstract class AbstractCollection
{
    /**
     * @readonly
     * @var array<TKey, TValue>
     */
    private array $items;

    /**
     * @param array<TKey, TValue> $items
     */
    final public function __construct(array $items)
    {
        $this->items = $items;
    }

    /**
     * @template TReturn
     * @template TInitial
     * @param callable(TInitial|TReturn|null,TValue):(TInitial|TReturn) $callback
     * @param TInitial|null $initial
     * @return TReturn|TInitial|null
     */    
    public function reduce(callable $callback, $initial = null)
    {
        return array_reduce($this->items, $callback, $initial);
    }
}

Gives

INFO: MixedReturnStatement - 32:16 - Could not infer a return type

INFO: MixedInferredReturnType - 28:16 - Could not verify return type 'TInitial|TReturn|null' for AbstractCollection::reduce

Can it be fixed?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/57243f56e5

<?php

/**
 * @template TKey as array-key
 * @template TValue as mixed
 */
abstract class AbstractCollection
{
    /**
     * @readonly
     * @var array<TKey, TValue>
     */
    private array $items;

    /**
     * @param array<TKey, TValue> $items
     */
    final public function __construct(array $items)
    {
        $this->items = $items;
    }

    /**
     * @template TReturn
     * @template TInitial
     * @param callable(TInitial|TReturn|null,TValue):(TInitial|TReturn) $callback
     * @param TInitial|null $initial
     * @return TReturn|TInitial|null
     */    
    public function reduce(callable $callback, $initial = null)
    {
        return array_reduce($this->items, $callback, $initial);
    }
}

Psalm output (using commit f07b6e6):

INFO: MixedReturnStatement - 32:16 - Could not infer a return type

INFO: MixedInferredReturnType - 28:16 - Could not verify return type 'TInitial|TReturn|null' for AbstractCollection::reduce

[orklah]

There is ArrayReduceReturnTypeProvider that handles this function's return type. If you want to take a look, please ask and I'll give you some pointers

[weirdan]

It seems to be fixed: https://psalm.dev/r/755aef1954

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/755aef1954

<?php

/**
 * @template TKey as array-key
 * @template TValue as mixed
 */
abstract class AbstractCollection
{
    /**
     * @readonly
     * @var array<TKey, TValue>
     */
    private array $items;

    /**
     * @param array<TKey, TValue> $items
     */
    final public function __construct(array $items)
    {
        $this->items = $items;
    }

    /**
     * @template TReturn
     * @template TInitial
     * @param callable(TInitial|TReturn|null,TValue):(TInitial|TReturn) $callback
     * @param TInitial|null $initial
     * @return TReturn|TInitial|null
     */    
    public function reduce(callable $callback, $initial = null)
    {
        return array_reduce($this->items, $callback, $initial);
    }
}

Psalm output (using commit 7869cb5):

No issues!