mirror of
https://github.com/danog/psalm.git
synced 2024-12-05 21:19:03 +01:00
158 lines
2.3 KiB
Markdown
158 lines
2.3 KiB
Markdown
# UnsafeGenericInstantiation
|
||
|
||
Emitted when an attempt is made to instantiate a class using `new static` without a constructor that's final:
|
||
|
||
```php
|
||
<?php
|
||
|
||
/**
|
||
* @template T
|
||
* @psalm-consistent-constructor
|
||
*/
|
||
class Container {
|
||
/**
|
||
* @var T
|
||
*/
|
||
public $t;
|
||
|
||
/**
|
||
* @param T $t
|
||
*/
|
||
public function __construct($t) {
|
||
$this->t = $t;
|
||
}
|
||
|
||
/**
|
||
* @template U
|
||
* @param U $u
|
||
* @return static<U>
|
||
*/
|
||
public function getInstance($u) : static
|
||
{
|
||
return new static($u);
|
||
}
|
||
}
|
||
```
|
||
|
||
|
||
## What’s wrong here?
|
||
|
||
The problem comes when extending the class:
|
||
|
||
```php
|
||
<?php
|
||
|
||
/**
|
||
* @template T
|
||
* @psalm-consistent-constructor
|
||
*/
|
||
class Container {
|
||
/**
|
||
* @var T
|
||
*/
|
||
public $t;
|
||
|
||
/**
|
||
* @param T $t
|
||
*/
|
||
public function __construct($t) {
|
||
$this->t = $t;
|
||
}
|
||
|
||
/**
|
||
* @template U
|
||
* @param U $u
|
||
* @return static<U>
|
||
*/
|
||
public function getInstance($u) : static
|
||
{
|
||
return new static($u);
|
||
}
|
||
}
|
||
|
||
/**
|
||
* @extends Container<string>
|
||
*/
|
||
class StringContainer extends Container {}
|
||
|
||
$c = StringContainer::getInstance(new stdClass());
|
||
// creates StringContainer<stdClass>, clearly invalid
|
||
```
|
||
|
||
## How to fix
|
||
|
||
Either use `new self` instead of `new static`:
|
||
|
||
```php
|
||
<?php
|
||
|
||
/**
|
||
* @template T
|
||
* @psalm-consistent-constructor
|
||
*/
|
||
class Container {
|
||
/**
|
||
* @var T
|
||
*/
|
||
public $t;
|
||
|
||
/**
|
||
* @param T $t
|
||
*/
|
||
public function __construct($t) {
|
||
$this->t = $t;
|
||
}
|
||
|
||
/**
|
||
* @template U
|
||
* @param U $u
|
||
* @return self<U>
|
||
*/
|
||
public function getInstance($u) : self
|
||
{
|
||
return new self($u);
|
||
}
|
||
}
|
||
```
|
||
|
||
Or you can add a `@psalm-consistent-templates` annotation which ensures that any child class has the same generic params:
|
||
|
||
```php
|
||
<?php
|
||
|
||
/**
|
||
* @template T
|
||
* @psalm-consistent-constructor
|
||
* @psalm-consistent-templates
|
||
*/
|
||
class Container {
|
||
/**
|
||
* @var T
|
||
*/
|
||
public $t;
|
||
|
||
/**
|
||
* @param T $t
|
||
*/
|
||
public function __construct($t) {
|
||
$this->t = $t;
|
||
}
|
||
|
||
/**
|
||
* @template U
|
||
* @param U $u
|
||
* @return static<U>
|
||
*/
|
||
public function getInstance($u) : static
|
||
{
|
||
return new static($u);
|
||
}
|
||
}
|
||
|
||
/**
|
||
* @template T
|
||
* @psalm-extends Container<T>
|
||
*/
|
||
class LazyLoadingContainer extends Container {}
|
||
```
|