vimeo/psalm

Different results between `DateTime` and `DateTimeImmutable`

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#5,220 opened on Feb 14, 2021

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Description

I noticed that DateTime and DateTimeImmutable works different way, but those should work as the same.

I first noticed this with PHP 8 named parameters and DateTimeImmutable usage, and I made fix for that part - https://github.com/vimeo/psalm/pull/5218

But now I'm still seeing different handling on DateTime class - and I cannot find the code where that is done.

https://psalm.dev/r/129b9fce2b https://psalm.dev/r/ee31f26136

Contributor guide

Research direction
Investigate the code path for DateTime vs DateTimeImmutable in Psalm's type system. Look at the handling of built in classes and named parameters. The issue is that DateTime has different behavior than DateTimeImmutable, but they should be consistent. Examine the PR #5218 as a reference for fixing similar issues.
Tech stack
php
Domain
backendtooling
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.
Half day
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.
Mostly clear
Prerequisites
PHP
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50