Bug report

From the below code the return type of sayHello() is specified in HelloWorldInterface.
When child class returns array its format is array{abc: int};

<?php declare(strict_types = 1);

interface HelloWorldInterface
{
	/**
	 * @return array{abc: int}|string
	 */
	public function sayHello();
}

class HelloWorld implements HelloWorldInterface
{
	/**
	 * @inheritDoc
	 */
	public function sayHello(): array
	{
		return [
			"abc" => 1,
		];
	}
}

I don't get why it is complaining.

Code snippet that reproduces the problem

https://phpstan.org/r/bbaf4883-1af5-45d7-b38d-7567e32eef99

Expected output

No errors.

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