Variable assignment inside if-statement gives unexpected type

[Cxarli]

Bug report

Version: PHPStan - PHP Static Analysis Tool 0.11.x-dev@f6fed5f (but also occurs on the web version)

If you assign a variable inside an if-statement, it seems the type hinting derived from the rest of that if-statement is lost inside the actual clause.

Code snippet that reproduces the problem

<?php
class TestClass {
    /**
     * @var string
     */
    public $field = 'value';
}

/**
 * @return TestClass|null
 */
function getTest() {
    // Impossible but successfully mutes the `Function getTest() never returns TestClass` warning
    if (1 + 1 == 3) return new TestClass;

    return null;
}

/**
 * @return void
 */
function main() {
    if (is_object($test = getTest())) {
        // Cannot access property $field on TestClass|null
        echo $test->field;
    }
}

https://phpstan.org/r/16f1a2ba-5624-4f82-b716-0544d7427594

Expected output

I didn't expect this warning to happen. If you place the assignment before the if-statement, everything is fine. The (private) code base I'm working on has this all over the place however, so it makes using phpstan a bit harder.

[cs278]

Confirmed this is still an issue in 0.12.

[guilliamxavier]

I stumbled upon the same issue with an if (is_string($x = get_string_or_false())) { /* $x is string but phpstan thinks is string|false */ }: https://phpstan.org/r/22136e13-8b8d-47e0-914e-13cab7476b82 (f1 warns, f2 doesn't)

[phpstan-bot]

@Cxarli PHPStan now reports different result with your code snippet:

@@ @@
-25: Cannot access property $field on TestClass|null.
+No errors

[phpstan-bot]

@Cxarli PHPStan now reports different result with your code snippet:

@@ @@
-25: Cannot access property $field on TestClass|null.
+ 6: Property TestClass::$field has no typehint specified.
+12: Function getTest() has no return typehint specified.
+22: Function main() has no return typehint specified.

Full report

Line	Error
6	Function main() has no return typehint specified.
12	Function main() has no return typehint specified.
22	Function main() has no return typehint specified.

[Cxarli]

That seems to fix it. Closed

[ondrejmirtes]

This issue isn't solved, it just moved to level 8: https://phpstan.org/r/c761685b-cc60-4d01-bbbd-c903d75453c2

[phpstan-bot]

@guilliamxavier After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-6: Parameter #1 $json of function json_decode expects string, string|false given.
+No errors

[phpstan-bot]

@ondrejmirtes After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-25: Cannot access property $field on TestClass|null.
+No errors

[ondrejmirtes]

Fixed: phpstan/phpstan-src@b2bf703

[github-actions]

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