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