Cannot combine generic key types when @template is limited to array-key #10871

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1. ondrejmirtes

   added

   bug

   on May 30, 2024
2. ondrejmirtes

   added this to the Generics milestone on May 30, 2024
3. SerethiX commented on Jul 23, 2024

   

   SerethiX

   on Jul 23, 2024

   More actions

   The type checking also seems to stop, once array-key is used.

   <?php declare(strict_types = 1);
   
   /** 
   -  * @template T of array-key
   +  * @template T of int|string
     * @param non-empty-array<T, mixed> $bar
     * @return T
     */
   function foo(array $bar): int|string {
       \PHPStan\dumpType($bar);
   	
   	int_only(array_key_first($bar));
   
   	return array_key_first($bar);
   }
   
   function int_only(int $param): void {
   }
   
   if (is_string(foo(['foo' => 'bar']))) echo 'is_string';
   if (is_int(foo(['bar']))) echo 'is_int';

   This example failes to detect the possible type error, while int|string correctly detects it: https://phpstan.org/r/8213d7d7-f36c-4e34-8fbf-64976a1dcde0
4. phpstan-bot commented on Feb 21, 2025

   

   phpstan-bot

   on Feb 21, 2025

   Contributor

   More actions

   @SerethiX After the latest push in 2.1.x, PHPStan now reports different result with your code snippet:

   @@ @@
    19: Call to function is_string() with 'foo' will always evaluate to true.
    20: Call to function is_int() with 0 will always evaluate to true.
    
   -PHP 7.3 – 7.4 (4 errors)
   +PHP 7.2 – 7.4 (4 errors)
    ==========
    
     8: Function foo() uses native union types but they're supported only on PHP 8.0 and later.
     9: Dumped type: non-empty-array<T of (int|string) (function foo(), argument), mixed>
   -19: Call to function is_string() with 'foo' will always evaluate to true.
   -20: Call to function is_int() with 0 will always evaluate to true.
   -
   -PHP 7.2 (6 errors)
   -==========
   -
   - 8: Function foo() uses native union types but they're supported only on PHP 8.0 and later.
   - 9: Dumped type: non-empty-array<T of (int|string) (function foo(), argument), mixed>
   -11: Function array_key_first not found.
   -13: Function array_key_first not found.
    19: Call to function is_string() with 'foo' will always evaluate to true.
    20: Call to function is_int() with 0 will always evaluate to true.

   Full report

   PHP 8.0 – 8.3 (3 errors)

   Line	Error
   9	`Dumped type: non-empty-array<T of (int
   19	Call to function is_string() with 'foo' will always evaluate to true.
   20	Call to function is_int() with 0 will always evaluate to true.

   PHP 7.2 – 7.4 (4 errors)

   Line	Error
   8	Function foo() uses native union types but they're supported only on PHP 8.0 and later.
   9	`Dumped type: non-empty-array<T of (int
   19	Call to function is_string() with 'foo' will always evaluate to true.
   20	Call to function is_int() with 0 will always evaluate to true.
5. phpstan-bot commented on Feb 21, 2025

   

   phpstan-bot

   on Feb 21, 2025

   Contributor

   More actions

   @SerethiX After the latest push in 2.1.x, PHPStan now reports different result with your code snippet:

   @@ @@
    19: Call to function is_string() with 'foo' will always evaluate to true.
    20: Call to function is_int() with 0 will always evaluate to true.
    
   -PHP 7.3 – 7.4 (5 errors)
   +PHP 7.2 – 7.4 (5 errors)
    ==========
    
     8: Function foo() uses native union types but they're supported only on PHP 8.0 and later.
     9: Dumped type: non-empty-array<T of int|string (function foo(), argument), mixed>
    11: Parameter #1 $param of function int_only expects int, T of int|string given.
   -19: Call to function is_string() with 'foo' will always evaluate to true.
   -20: Call to function is_int() with 0 will always evaluate to true.
   -
   -PHP 7.2 (6 errors)
   -==========
   -
   - 8: Function foo() uses native union types but they're supported only on PHP 8.0 and later.
   - 9: Dumped type: non-empty-array<T of int|string (function foo(), argument), mixed>
   -11: Function array_key_first not found.
   -13: Function array_key_first not found.
    19: Call to function is_string() with 'foo' will always evaluate to true.
    20: Call to function is_int() with 0 will always evaluate to true.

   Full report

   PHP 8.0 – 8.3 (4 errors)

   Line	Error
   9	`Dumped type: non-empty-array<T of int
   11	`Parameter #1 $param of function int_only expects int, T of int
   19	Call to function is_string() with 'foo' will always evaluate to true.
   20	Call to function is_int() with 0 will always evaluate to true.

   PHP 7.2 – 7.4 (5 errors)

   Line	Error
   8	Function foo() uses native union types but they're supported only on PHP 8.0 and later.
   9	`Dumped type: non-empty-array<T of int
   11	`Parameter #1 $param of function int_only expects int, T of int
   19	Call to function is_string() with 'foo' will always evaluate to true.
   20	Call to function is_int() with 0 will always evaluate to true.
6. phpstan-bot commented on Sep 9, 2026

   

   phpstan-bot

   on Sep 9, 2026

   Contributor

   More actions

   Closed via merging phpstan/phpstan-src#6376
7. phpstan-bot

   closed this as completedon Sep 9, 2026
8. github-actions commented on Oct 11, 2026

   

   github-actionsBot

   on Oct 11, 2026 – with GitHub Actions

   More actions

   This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
9. github-actions

   locked as resolved and limited conversation to collaborators on Oct 11, 2026