vimeo/psalm

`array_splice` type and side effects not handled properly

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#8,202 opened on Jun 29, 2022

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Help wantedeasy problemsenhancementgood first issue

Description

I recently updated to 5.0.0-beta1 for a PHP 8.1-based project, and now I'm getting an error reported with array_splice().

https://psalm.dev/r/367fd63316

I'm having PHP take a chunk of items off an array in C code, so it takes fewer interpreter steps to get the work done. But Psalm doesn't seem to realize that the return value from splice matches the input type (including preserving string keys), or that the splice changes the array it is given.

Building the equivalent with a for-loop and array_shift() is accepted, or else there is an error in my own understanding.

I'm unsure when I last checked this exact code in Psalm 4.x. The exact version I'm using reports itself as Psalm 5.0.0-beta1@f960d71b7e8dccb0815bce28a22a33ce5410e361.

Contributor guide

Tech stack
None
Domain
developer experiencetooling
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.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
PHPPsalmstatic analysisarray functions
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate how Psalm models the `array splice` function. Look at the function stub definitions in `stubs/` directory, specifically the PHP native function stubs. The issue reports that the return type and side effects are incorrect. Check the existing tests for array splice and consider updating the type definitions or the internal handling of array operations.