False positive: Dead catch

Bug report

I'm working on a new version of my library and I have an abstract class that contain this method:

\Phpfastcache\Core\Pool\DriverPoolAbstractTrait

    /**
     * @param ExtendedCacheItemInterface ...$items
     * @return array<array<string, mixed>>
     * @throws PhpfastcacheUnsupportedMethodException
     */
    protected function driverReadMultiple(ExtendedCacheItemInterface ...$items): array
    {
        throw new PhpfastcacheUnsupportedMethodException();
    }

And I do have multiple child class that extends the abstract class, but for compatibility reason some child class override the driverReadMultiple method, and some aren't.

But Phpstan still returns me this error:

 ------ --------------------------------------------------------------------------------------------------------------- 
  Line   Phpfastcache\Core\Pool\CacheItemPoolTrait.php (in context of class Phpfastcache\Drivers\Redis\DriverAbstract)
 ------ ---------------------------------------------------------------------------------------------------------------
  138    Dead catch - Phpfastcache\Exceptions\PhpfastcacheUnsupportedMethodException is never thrown in the try block.
 ------ ---------------------------------------------------------------------------------------------------------------

\Phpfastcache\Core\Pool\CacheItemPoolTrait
This is the "guilty" code:

                try {
                    $driverArrays = $this->driverReadMultiple(...$items);
                } catch (PhpfastcacheUnsupportedMethodException) {
                    /**
                     * Fallback for drivers that does not yet implement driverReadMultiple() method.
                     */
                    $driverArrays = array_combine(
                        array_map(fn($item) => $item->getKey(), $items),
                        array_map(fn($item) => $this->driverRead($item), $items)
                    );
                }

At the moment of this call, from a static analysis point of view, the code is not aware of the child implementing it.

I tried to reproduce it with Phpstan playground, but I think its too specific to Phpfastcache architecture :(

Code snippet that reproduces the problem

No response

Expected output

No error

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It helps me a lot since years thanks again :smi

This bug report is missing a link to reproduction at phpstan.org/try.

It will most likely be closed after manual review.

It shouldn't that hard to create a reproducer...

If I understood correctly the phpfastcache code, it should be something like
https://phpstan.org/r/78c48681-6423-4652-a7f3-0f46c516505b

It shouldn't that hard to create a reproducer...

If I understood correctly the phpfastcache code, it should be something like https://phpstan.org/r/78c48681-6423-4652-a7f3-0f46c516505b

Yeah, exactly, I struggled trying to reproduce it for an hour, but I gave up after being unable to reproduce the behavior. Thanks

@VincentLanglet

@VincentLanglet @Geolim4 After the latest push in 2.0.x, PHPStan now reports different result with your code snippet:

@@ @@
-PHP 8.0 – 8.3 (1 error)
+PHP 8.1 – 8.3 (1 error)
 ==========
 
 12: Dead catch - Exception is never thrown in the try block.
 
-PHP 7.2 – 7.4 (3 errors)
+PHP 8.0 (4 errors)
 ==========
 
+39: Tip: Method Foo2::doThings() always throws an exception, it should have return type "never".
+39: Method Foo2::doThings() has invalid return type never.
 12: Dead catch - Exception is never thrown in the try block.
+11: Method Foo2::driverReadMultiple() should return array but returns never.
+
+PHP 7.2 – 7.4 (6 errors)
+==========
+
+39: Tip: Method Foo2::doThings() always throws an exception, it should have return type "never".
+39: Method Foo2::doThings() has invalid return type never.
+12: Dead catch - Exception is never thrown in the try block.
 12: Non-capturing catch is supported only on PHP 8.0 and later.
+11: Method Foo2::driverReadMultiple() should return array but returns never.
 12: Non-capturing catch is supported only on PHP 8.0 and later.

Full report

PHP 8.1 – 8.3 (1 error)

Line	Error
12	`Dead catch - Exception is never thrown in the try block.`

PHP 8.0 (4 errors)

Line	Error
39	`Tip: Method Foo2::doThings() always throws an exception, it should have return type "never".`
39	`Method Foo2::doThings() has invalid return type never.`
12	`Dead catch - Exception is never thrown in the try block.`
11	`Method Foo2::driverReadMultiple() should return array but returns never.`

PHP 7.2 – 7.4 (6 errors)

Line	Error
39	`Tip: Method Foo2::doThings() always throws an exception, it should have return type "never".`
39	`Method Foo2::doThings() has invalid return type never.`
12	`Dead catch - Exception is never thrown in the try block.`
12	`Non-capturing catch is supported only on PHP 8.0 and later.`
11	`Method Foo2::driverReadMultiple() should return array but returns never.`
12	`Non-capturing catch is supported only on PHP 8.0 and later.`

@VincentLanglet

@VincentLanglet @Geolim4 After the latest push in 2.0.x, PHPStan now reports different result with your code snippet:

@@ @@
-PHP 8.0 – 8.3 (1 error)
+PHP 8.1 – 8.3 (1 error)
 ==========
 
 12: Dead catch - Exception is never thrown in the try block.
 
-PHP 7.2 – 7.4 (3 errors)
+PHP 8.0 (4 errors)
 ==========
 
+39: Tip: Method Foo2::doThings() always throws an exception, it should have return type "never".
+39: Method Foo2::doThings() has invalid return type never.
 12: Dead catch - Exception is never thrown in the try block.
+11: Method Foo2::driverReadMultiple() should return array<mixed> but returns never.
+
+PHP 7.2 – 7.4 (6 errors)
+==========
+
+39: Tip: Method Foo2::doThings() always throws an exception, it should have return type "never".
+39: Method Foo2::doThings() has invalid return type never.
+12: Dead catch - Exception is never thrown in the try block.
 12: Non-capturing catch is supported only on PHP 8.0 and later.
+11: Method Foo2::driverReadMultiple() should return array<mixed> but returns never.
 12: Non-capturing catch is supported only on PHP 8.0 and later.

Full report

PHP 8.1 – 8.3 (1 error)

Line	Error
12	`Dead catch - Exception is never thrown in the try block.`

PHP 8.0 (4 errors)

Line	Error
39	`Tip: Method Foo2::doThings() always throws an exception, it should have return type "never".`
39	`Method Foo2::doThings() has invalid return type never.`
12	`Dead catch - Exception is never thrown in the try block.`
11	`Method Foo2::driverReadMultiple() should return array<mixed> but returns never.`

PHP 7.2 – 7.4 (6 errors)

Line	Error
39	`Tip: Method Foo2::doThings() always throws an exception, it should have return type "never".`
39	`Method Foo2::doThings() has invalid return type never.`
12	`Dead catch - Exception is never thrown in the try block.`
12	`Non-capturing catch is supported only on PHP 8.0 and later.`
11	`Method Foo2::driverReadMultiple() should return array<mixed> but returns never.`
12	`Non-capturing catch is supported only on PHP 8.0 and later.`

Fix false positive dead catch when overriding non-abstract trait meth…

If I understood correctly the phpfastcache code, it should be something like
phpstan.org/r/78c48681-6423-4652-a7f3-0f46c516505b

I think a possible fix should be similar to what was done in phpstan/phpstan-src#5309

similar suggestions were made for property access

Avoid dead catch false positive for inconsistently overridden trait m…

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False positive: Dead catch #10315

Bug report

Code snippet that reproduces the problem

Expected output

Did PHPStan help you today? Did it make you happy in any way?

PHP 8.1 – 8.3 (1 error)

PHP 8.0 (4 errors)

PHP 7.2 – 7.4 (6 errors)

PHP 8.1 – 8.3 (1 error)

PHP 8.0 (4 errors)

PHP 7.2 – 7.4 (6 errors)

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False positive: Dead catch #10315

Description

Bug report

Code snippet that reproduces the problem

Expected output

Did PHPStan help you today? Did it make you happy in any way?

Activity

mergeable commented on Dec 15, 2023

VincentLanglet commented on Dec 24, 2023

Geolim4 commented on Dec 25, 2023

phpstan-bot commented on Sep 4, 2024

PHP 8.1 – 8.3 (1 error)

PHP 8.0 (4 errors)

PHP 7.2 – 7.4 (6 errors)

phpstan-bot commented on Oct 12, 2024

PHP 8.1 – 8.3 (1 error)

PHP 8.0 (4 errors)

PHP 7.2 – 7.4 (6 errors)

staabm commented on May 5, 2026

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