Generics on Interfaces

[bebetoalves]

Hello, I have an interface that implements a method which takes an array of format X and returns an array with the same format X. I tried using generics to express this, but apparently I can't do so because I'm getting "ImplementedReturnTypeMismatch" and "MoreSpecificImplementedParamType" errors.

https://psalm.dev/r/5dd25daf35

<?php

interface Processor
{
    /**
     * @template TKey of array-key
     * @template TValue 
     * @param array<TKey, TValue> $data
     * @return array<TKey, TValue>
     */
    public function process(array $data): array;
}

class QueryProcessor implements Processor
{
    /**
     * @param array{string, list<int>} $data
     * @return array{string, list<int>}
     */
    public function process(array $data): array
    {
        [$query, $parameters] = $data;

        // some data process here

        return [$query, $parameters];
    }
}

class OutputProcessor implements Processor
{
    /**
     * @param list<string> $data
     * @return list<string>
     */
    public function process(array $data): array
    {
        // some data process here

        return $data;
    }
}

$query = new QueryProcessor();
$query->process(['query', [1,2,3]]);

$data = new OutputProcessor();
$data->process(['abc']);

[weirdan]

You just need to lift the generic type param to the interface level: https://psalm.dev/r/c82c7ea6f2