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Error Identifier: conditionalType.subjectNotFound

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

class Foo
{
    /**
     * @return ($value is string ? int : bool)
     */
    public function doFoo(mixed $value): int|bool
    {
        // ...
    }
}

Why is it reported? #

A conditional return type uses a subject type that does not reference any @template tag. In a class method without @template tags, the subject of a conditional type must refer to a parameter using the $param is Type syntax rather than a bare type name.

How to fix it #

If the condition depends on a parameter, use the $param is Type syntax:

 <?php declare(strict_types = 1);
 
 class Foo
 {
     /**
-     * @return ($value is string ? int : bool)
+     * @param string|int $value
+     * @return ($value is string ? int : bool)
      */
-    public function doFoo(mixed $value): int|bool
+    public function doFoo(string|int $value): int|bool
     {
         // ...
     }
 }

If you intend to use a template type as the subject, declare it with @template:

 <?php declare(strict_types = 1);
 
 class Foo
 {
     /**
+     * @template T
-     * @return (int is string ? int : bool)
+     * @return (T is string ? int : bool)
      */
-    public function doFoo(mixed $value): int|bool
+    public function doFoo(mixed $value): int|bool
     {
         // ...
     }
 }

How to ignore this error #

You can use the identifier conditionalType.subjectNotFound to ignore this error using a comment:

// @phpstan-ignore conditionalType.subjectNotFound
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: conditionalType.subjectNotFound

Rules that report this error #

• PHPStan\Rules\PhpDoc\FunctionConditionalReturnTypeRule [1]
• PHPStan\Rules\PhpDoc\MethodConditionalReturnTypeRule [1]

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