False-positive "not matching the resolved parameter type" with $_POST

[Dmitrii Kustov]

Subject	Details
Plugin	Php Inspections (EA Extended)
Language level	PHP 8.3

Current behaviour

Code like

public function setAvatar(string $fileid = ''): array
{
    $fileid = $_POST['avatar'] ?? $fileid ?? '';
    return [];
}

results in [EA] New value type (array) is not matching the resolved parameter type and might introduce types-related false-positives. on line 3.
Adding is_string check for $_POST['avatar'] before this does not help, either (now on line 4)

public function setAvatar(string $fileid = ''): array
{
    if (is_string($_POST['avatar'])) {
        $fileid = $_POST['avatar'];
    }
    $fileid = $fileid ?? '';
    return [];
}

The only way to "fix" this is to change type of $fileid by allowing array:

public function setAvatar(string|array $fileid = ''): array
{
    $fileid = $_POST['avatar'] ?? $fileid ?? '';
    return [];
}

Which suggests that $_POST['avatar'] is interpreted as array regardless, even though, technically, it should be mixed.

Expected behaviour

While it may be a valid point to mark the first example as potential issue, second example with type check should not be marked, at all. This may be related to #1930, but creating as a new bug, since description seem to suggest a different set of expectations, which may be specific to example there.

Environment details

PhpStorm 2023.3.6
Build #PS-233.15026.12, built on March 21, 2024
Licensed to simbiat.ru / Dmitry Kustov
Subscription is active until May 11, 2024.
For non-commercial open source development only.
Runtime version: 17.0.10+1-b1087.23 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Windows 11.0
GC: G1 Young Generation, G1 Old Generation
Memory: 5120M
Cores: 16
Registry:
  debugger.new.tool.window.layout=true
  run.processes.with.pty=TRUE
  ide.experimental.ui=true
Non-Bundled Plugins:
  com.jetbrains.space (233.15026.16)
  com.kalessil.phpStorm.phpInspectionsEA (5.0.0.0)

[Joe Theuerkauf]

i wonder where the inspection is getting array as a possible assignment type... Is it because you're returning [], which is never assigned to the variable in the first place?

What happens if you change the return type to string and return '';?

Strange behavior.

[Dmitrii Kustov]

This is not related to return type (and changing it will not do anything), but to the fact, that function defines type for $fileid, and I am then assigning to it something, that can be not a string. $_POST['avatar'] is treated as mixed, but array is probably taken from $_POST, which is, indeed, an array.