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Error Identifier: method.shadowTemplate

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);

/**
 * @template T of \Exception
 */
class ErrorHandler
{
	/**
	 * @template T
	 * @param T $value
	 * @return T
	 */
	public function handle($value)
	{
		return $value;
	}
}

Why is it reported? #

A method declares a @template type parameter with the same name as one already declared on its containing class. The method-level template type T shadows the class-level template type T, which makes it impossible to reference the class template type from within the method. This is confusing and likely a mistake.

In the example above, the class declares @template T of \Exception, but the method also declares @template T (without the bound). Inside the method, T refers to the method’s template type, not the class-level one.

How to fix it #

Rename the method-level template type to avoid the conflict:

 <?php declare(strict_types = 1);
 
 /**
  * @template T of \Exception
  */
 class ErrorHandler
 {
 	/**
-	 * @template T
-	 * @param T $value
-	 * @return T
+	 * @template U
+	 * @param U $value
+	 * @return U
 	 */
 	public function handle($value)
 	{
 		return $value;
 	}
 }

If the method intends to use the class-level template type, remove the @template declaration from the method:

 /**
  * @template T of \Exception
  */
 class ErrorHandler
 {
 	/**
-	 * @template T
 	 * @param T $value
 	 * @return T
 	 */
 	public function handle($value)
 	{
 		return $value;
 	}
 }

How to ignore this error #

You can use the identifier method.shadowTemplate to ignore this error using a comment:

// @phpstan-ignore method.shadowTemplate
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: method.shadowTemplate

Rules that report this error #

• PHPStan\Rules\Generics\MethodTemplateTypeRule [1]

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