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BenevolentUnionType with generics produce confusing errors #9732

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Closed
BenevolentUnionType with generics produce confusing errors#9732
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bug
Milestone
Easy fixes

Description

@dktapps
dktapps
opened on Aug 7, 2023

Bug report

When passing $GLOBALS to a function which accepts array<K of string, V>, K is not able to be inferred for some reason.

This started getting reported around 1.10.17 or so.

Code snippet that reproduces the problem

https://phpstan.org/r/63496f72-9ba6-4b08-b393-1442222c6e39

Expected output

The error on line 23 should not be reported, as the type of $GLOBALS is array<string, mixed>.

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Activity

  1. ondrejmirtes
    added
    bug
    on Aug 7, 2023
  2. ondrejmirtes
    added this to the Easy fixes milestone on Aug 7, 2023

  3. dktapps commented on Sep 21, 2023

    @dktapps
    dktapps
    on Sep 21, 2023
    ContributorAuthor

    Seems like this is something to do with the BenevolentUnionType used for the keys of globals. The same also happens with $_SERVER and other superglobals.

    Again, I'd be happy to work on a fix if I can get a pointer where to start looking for the problem.

  4. ondrejmirtes commented on Sep 21, 2023

    @ondrejmirtes
    ondrejmirtes
    on Sep 21, 2023
    Member

    I'd look what happens in ArrayType::inferTemplateTypes() first.

  5. dktapps commented on Sep 21, 2023

    @dktapps
    dktapps
    on Sep 21, 2023
    ContributorAuthor

    Thanks, I'll take a look.

  6. dktapps commented on Sep 21, 2023

    @dktapps
    dktapps
    on Sep 21, 2023
    ContributorAuthor

    Looks like the problem is actually the type itself, rather than the superglobals. I assumed that $GLOBALS would be considered to have type array<string, mixed>. When using an array with array-key for the key, the problem is the same.

    It appears that the real issue here is BenevolentUnionType is suppressing the errors that would make this problem understandable.
    When using a non-benevolent type like array<int|string, mixed> it reports two errors, the second of which makes it very clear where the problem is coming from (see line 34 errors):
    https://phpstan.org/r/a24f065e-16d5-46a4-bc4f-11db8605284c

  7. dktapps
    changed the title [-]Generic key inference from $GLOBALS fails[/-] [+]BenevolentUnionType with generics produce confusing errors[/+] on Sep 21, 2023

  8. dktapps commented on Sep 21, 2023

    @dktapps
    dktapps
    on Sep 21, 2023
    ContributorAuthor

    Related PR: phpstan/phpstan-src#2446

  9. phpstan-bot commented on Sep 26, 2025

    @phpstan-bot
    phpstan-bot
    on Sep 26, 2025
    Contributor

    @dktapps After the latest push in 2.1.x, PHPStan now reports different result with your code snippet:

    @@ @@
 16: No error to ignore is reported on line 16.
-23: Unable to resolve the template type TKeyType in call to method static method HelloWorld::stringifyKeys()
+23: Unable to resolve the template type TKeyType in call to static method HelloWorld::stringifyKeys()
    Full report
    Line Error
    16 No error to ignore is reported on line 16.
    23 Unable to resolve the template type TKeyType in call to static method HelloWorld::stringifyKeys()

  10. phpstan-bot commented on Sep 26, 2025

    @phpstan-bot
    phpstan-bot
    on Sep 26, 2025
    Contributor

    @dktapps After the latest push in 2.1.x, PHPStan now reports different result with your code snippet:

    @@ @@
-26: Unable to resolve the template type TKeyType in call to method static method HelloWorld::stringifyKeys()
+26: Unable to resolve the template type TKeyType in call to static method HelloWorld::stringifyKeys()
 34: Parameter #1 $array of static method HelloWorld::stringifyKeys() expects array<string, mixed>, array<int|string, mixed> given.
-34: Unable to resolve the template type TKeyType in call to method static method HelloWorld::stringifyKeys()
+34: Unable to resolve the template type TKeyType in call to static method HelloWorld::stringifyKeys()
    Full report
    Line Error
    26 Unable to resolve the template type TKeyType in call to static method HelloWorld::stringifyKeys()
    34 `Parameter #1 $array of static method HelloWorld::stringifyKeys() expects array<string, mixed>, array<int
    34 Unable to resolve the template type TKeyType in call to static method HelloWorld::stringifyKeys()
  11. phpstan-bot
    added a commit that references this issue on Feb 27, 2026

    Fix BenevolentUnionType with generics producing false positive errors

    43dc704
  12. VincentLanglet
    added a commit that references this issue on Mar 2, 2026

    Fix phpstan/phpstan#9732: BenevolentUnionType with generics produce c…

    0a4583d

  13. phpstan-bot commented on Mar 2, 2026

    @phpstan-bot
    phpstan-bot
    on Mar 2, 2026
    Contributor

    Closed via merging phpstan/phpstan-src#5070

  14. phpstan-bot
    closed this as completedon Mar 2, 2026
  15. phpstan-bot
    added 2 commits that reference this issue on Mar 2, 2026

    Updated PHPStan to commit 0a4583df557c63266808465d2f7b9ac518e6814f

    0a4583d

    Updated PHPStan to commit dcfce1012b16e49d56e1bd1b0abe39ae97b4ec36

    dcfce10

  16. github-actions commented on Apr 3, 2026

    @github-actions
    github-actionsBot
    on Apr 3, 2026 – with GitHub Actions

    This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.

  17. github-actions
    locked as resolved and limited conversation to collaborators on Apr 3, 2026
  18. phpstan-bot
    added a commit that references this issue on Apr 7, 2026

    Fix phpstan/phpstan#9732: BenevolentUnionType with generics produce c…

    f7c2d72
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