minor #2859 clarify the type of returned loaders (xabbuh)
minor #2859 clarify the type of returned loaders (xabbuh)

This PR was merged into the 1.x branch.

Discussion
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clarify the type of returned loaders

Commits
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0eb29aa5 clarify the type of returned loaders

nicolas-grekas/Twig,twigphp/Twig,nicolas-grekas/Twig,twigphp/Twig,nicolas-grekas/Twig,nicolas-grekas/Twig,twigphp/Twig,nicolas-grekas/Twig