infer closure type from being passed into function's return type with callable signature

Bug report

I have a closure that passes a closure-parameter to an external method.

<?php

class A {
	/**
	 * @param array{string, int, bool} $array
	 */
	public function do(array $array): B
	{
		return new B;
	}
}

class B {}

class C {
	public function __construct(private A $a) {}

	/**
	 * @return Callable(array{string, int, bool}): B
	 */
	public function getCallable(): Callable
	{
		/**
		 * @param array{string, int, bool}
		 */
		return function (array $array): B 
		{
			return $this->a->do($array);
		};
	}
}

The closure return type has been declared with the correct parameter-type and inside the function the parameteres of the returned closure are also declared correctly.

Yet PHPStan complaints that the function called within the closure "expects array{string, int, bool}, array given".

I am sure I am missing something somewhere as I doubt that I am the only one stumbling over this.

Code snippet that reproduces the problem

https://phpstan.org/r/799ddd60-8c84-485c-bb0b-46b700bf2635

Expected output

No errors

Did PHPStan help you today? Did it make you happy in any way?

No response

I figured I could "fix" this by adding a /** @var array{string, int, bool} $array */ right before passing the variable inside the closure. But that seems to be a hacky patch for something that should be solved differently as all the information should already be available.

See https://phpstan.org/r/c6ef9c9b-8444-4b45-a3de-5493de78738a

Hello Andreas,
PHPStan currently doesn't read PHPDocs above closures so this PHPDoc is not used at all:

		/**
		 * @param array{string, int, bool}
		 */
		return function (array $array): B 
		{
			return $this->a->do($array);
		};

And there's a feature request for this already: #3770

The reason why we didn't add this yet is because PHPStan is pretty smart about inferring closure parameter and return type automatically based on where the closure is passed to. Some examples:

Closure passed to array_map and array_filter will correctly get the parameter type based on the array passed into the function call: https://phpstan.org/r/c3921b14-1546-4848-8058-07d149e98f4a
Closure passed to a parameter with the correct callable signature will correctly get the parameter type based on the signature: https://phpstan.org/r/377e784b-a102-4c54-932f-c6b091136764
Recently added *ClosureTypeExtensions that allow Larastan to infer precise closure type with custom logic:

User::doesntHave('accounts', 'and', function (Builder $query) {
    // Builder<Account> because it figures that out based on `User` and `accounts`
    \PHPStan\dumpType($query);
});

So in my experience this is much better than requiring the user to write @param and @return above their closures.

I'm typing this all out because I have a similar suggestion here. When looking at the code sample, PHPStan could figure out what's going to be passed into the closure based on the @return above the method thanks to the fact the closure is directly in return statement:

	/**
	 * @return callable(array{string, int, bool}): B
	 */
	public function getCallable(): callable
	{
		return function (array $array): B 
		{
			\PHPStan\dumpType($array); // array{string, int, bool}
			return $this->a->do($array);
		};
	}
}

WDYT?

@ondrejmirtes

Hey @ondrejmirtes.

Adding the PHPDoc above the closure was merely a try to see whether it fixes the issue. I would be totally happy for PHPStan to infer the type from the @return annotation of the function returning the callable as you have sketched out above!

But I did get you right that that is an idea how to solve that and not yet working code, didn't I? 'Cause currently the PHPSTan\dumpType() merely prints array...

Yes, it's just a suggestion how PHPStan could be improved 😊

@heiglandreas

@heiglandreas After the latest push in 2.0.x, PHPStan now reports different result with your code snippet:

@@ @@
-PHP 8.0 – 8.3 (1 error)
+PHP 8.0 – 8.3 (2 errors)
 ==========
 
+26: PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40
 28: Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.
 
-PHP 7.2 – 7.4 (2 errors)
+PHP 7.2 – 7.4 (3 errors)
 ==========
 
 16: Promoted properties are supported only on PHP 8.0 and later.
+26: PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40
 28: Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.

Full report

PHP 8.0 – 8.3 (2 errors)

Line	Error
26	`PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40`
28	`Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.`

PHP 7.2 – 7.4 (3 errors)

Line	Error
16	`Promoted properties are supported only on PHP 8.0 and later.`
26	`PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40`
28	`Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.`

@heiglandreas

@heiglandreas After the latest push in 2.0.x, PHPStan now reports different result with your code snippet:

@@ @@
-PHP 8.0 – 8.3 (1 error)
+PHP 8.0 – 8.3 (2 errors)
 ==========
 
+24: PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40
 28: Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.
 
-PHP 7.2 – 7.4 (2 errors)
+PHP 7.2 – 7.4 (3 errors)
 ==========
 
 16: Promoted properties are supported only on PHP 8.0 and later.
+24: PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40
 28: Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.

Full report

PHP 8.0 – 8.3 (2 errors)

Line	Error
24	`PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40`
28	`Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.`

PHP 7.2 – 7.4 (3 errors)

Line	Error
16	`Promoted properties are supported only on PHP 8.0 and later.`
24	`PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40`
28	`Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.`

@heiglandreas

@heiglandreas After the latest push in 2.0.x, PHPStan now reports different result with your code snippet:

@@ @@
-PHP 8.0 – 8.3 (1 error)
+PHP 8.0 – 8.3 (2 errors)
 ==========
 
+24: PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40 on line 2
 28: Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.
 
-PHP 7.2 – 7.4 (2 errors)
+PHP 7.2 – 7.4 (3 errors)
 ==========
 
 16: Promoted properties are supported only on PHP 8.0 and later.
+24: PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40 on line 2
 28: Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.

Full report

PHP 8.0 – 8.3 (2 errors)

Line	Error
24	`PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40 on line 2`
28	`Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.`

PHP 7.2 – 7.4 (3 errors)

Line	Error
16	`Promoted properties are supported only on PHP 8.0 and later.`
24	`PHPDoc tag @param has invalid value (array{string, int, bool}): Unexpected token "\n\t\t ", expected variable at offset 40 on line 2`
28	`Parameter #1 $array of method A::do() expects array{string, int, bool}, array given.`

It's very easy to implement. We need to update this place: https://github.com/phpstan/phpstan-src/blob/88d5b8cf0cb2da8873dc33222b5f8b4727f0756a/src/Analyser/NodeScopeResolver.php#L757-L761

And call processClosureNode / processArrowFunctionNode with the method's return type as $passedToType.

Add regression test for #11317

@ondrejmirtes

@ondrejmirtes After the latest push in 2.2.x, PHPStan now reports different result with your code snippet:

@@ @@
+10: Call to function array_map() on a separate line has no effect.
 11: Dumped type: int

Full report

Line	Error
10	`Call to function array_map() on a separate line has no effect.`
11	`Dumped type: int`

Add regression test for #11317

Updated PHPStan to commit c871d1f9a556bb764f0a4527032ceeebe17437de

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infer closure type from being passed into function's return type with callable signature #11317

Bug report

Code snippet that reproduces the problem

Expected output

Did PHPStan help you today? Did it make you happy in any way?

PHP 8.0 – 8.3 (2 errors)

PHP 7.2 – 7.4 (3 errors)

PHP 8.0 – 8.3 (2 errors)

PHP 7.2 – 7.4 (3 errors)

PHP 8.0 – 8.3 (2 errors)

PHP 7.2 – 7.4 (3 errors)

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infer closure type from being passed into function's return type with callable signature #11317

Description

Bug report

Code snippet that reproduces the problem

Expected output

Did PHPStan help you today? Did it make you happy in any way?

Activity

heiglandreas commented on Jul 10, 2024

ondrejmirtes commented on Jul 10, 2024

heiglandreas commented on Jul 11, 2024

ondrejmirtes commented on Jul 11, 2024

phpstan-bot commented on Sep 4, 2024

PHP 8.0 – 8.3 (2 errors)

PHP 7.2 – 7.4 (3 errors)

phpstan-bot commented on Sep 7, 2024

PHP 8.0 – 8.3 (2 errors)

PHP 7.2 – 7.4 (3 errors)

phpstan-bot commented on Sep 8, 2024

PHP 8.0 – 8.3 (2 errors)

PHP 7.2 – 7.4 (3 errors)

ondrejmirtes commented on Nov 3, 2024

phpstan-bot commented on Jul 7, 2026

github-actions commented on Oct 29, 2026

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