vimeo/psalm

Emit an issue when using coalesce operator if the first operand can't be null

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#7,101 opened on Dec 8, 2021

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 (10 comments) (0 reactions) (0 assignees)PHP (668 forks)batch import
Help wantedenhancement

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Description

https://psalm.dev/r/154ffd42b2

/** @var string $q */
$a = explode(',', $q);

return $a[0] ?? '';

Should've resulted in TypeDoesNotContainNull but not.

Compare with:

https://3v4l.org/pgbW6

Contributor guide

Research direction
Investigate why Psalm does not emit TypeDoesNotContainNull when using the null coalesce operator on an array access that is guaranteed non null. Check the handling of array access types and the null coalesce operator in Psalm's type system.
Tech stack
php
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
PHPGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60