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psalm/docs/running_psalm/issues/DuplicateArrayKey.md
AndrolGenhald 3ce41d71a4
Clean up issues list, add documentation to help with named variadic confusion. (#5511)
* Clean up issues list, add documentation to help with named variadic confusion.

* Add ComplexFunction and ComplexMethod back to issues list.

I removed them because the documentation files don't exist, but they're used and the documentation just needs to be added.
2021-03-29 15:10:49 -04:00

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# DuplicateArrayKey
Emitted when an array has a key more than once
```php
<?php
$arr = [
'a' => 'one',
'b' => 'two',
'c' => 'this text will be overwritten by the next line',
'c' => 'three',
];
```
This can be caused by variadic arguments if `@no-named-arguments` is not specified:
```php
<?php
function foo($bar, ...$baz): array
{
return [$bar, ...$baz]; // $baz is array<array-key, mixed> since it can have named arguments
}
```
## How to fix
Remove the offending duplicates:
```php
<?php
$arr = [
'a' => 'one',
'b' => 'two',
'c' => 'three',
];
```
The first matching `'c'` key was removed to prevent a change in behaviour (any new duplicate keys overwrite the values of previous ones).