Array reduce not understanding callback return with generics

[BackEndTea]

Bug report

It seems array_reduce doesn't completely understand the return from the generics.

Code snippet that reproduces the problem

https://phpstan.org/r/e5bcd1ac-83f1-485a-98cd-0d11d1c3386f

Expected output

I expected no errors here

[phpstan-bot]

@BackEndTea After the latest push in 1.9.x, PHPStan now reports different result with your code snippet:

@@ @@
-PHP 8.0 – 8.2 (1 error)
+PHP 8.0 – 8.2
 ==========
 
-18: Method Inheritance::inherit() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<string>.
+No errors
 
-PHP 7.1 – 7.4 (2 errors)
+PHP 7.1 – 7.4 (1 error)
 ==========
 
-18: Method Inheritance::inherit() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<string>.
 33: Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.

Full report

PHP 8.0 – 8.2

No errors

PHP 7.1 – 7.4 (1 error)

Line	Error
33	Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.

[github-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.

[ondrejmirtes]

This issue was never fixed, but merely silenced...

[phpstan-bot]

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

@@ @@
 
 18: Method Inheritance::inherit() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<string>.
 
-PHP 7.1 – 7.4 (2 errors)
+PHP 7.1 – 7.4 (9 errors)
 ==========
 
 18: Method Inheritance::inherit() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<string>.
-33: Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
+33: Method Inheritance::callBack() has parameter $carry with no value type specified in iterable type array.
+33: Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
+33: PHPDoc tag @param for parameter $carry with type array<TKey of (int|string), TValues of bool|float|int|string|null>|null is not subtype of native type array|null.
+33: Parameter $carry of method Inheritance::callBack() has invalid type null.
+35: Strict comparison using === between array|null and null will always evaluate to false.
+39: Argument of an invalid type array|null supplied for foreach, only iterables are supported.
+44: Cannot access offset (int|string) on array|null.
+47: Method Inheritance::callBack() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array|null.

Full report

PHP 8.0 – 8.2 (1 error)

Line	Error
18	`Method Inheritance::inherit() should return array<TKey of (int

PHP 7.1 – 7.4 (9 errors)

Line	Error
18	`Method Inheritance::inherit() should return array<TKey of (int
33	Method Inheritance::callBack() has parameter $carry with no value type specified in iterable type array.
33	Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
33	`PHPDoc tag @param for parameter $carry with type array<TKey of (int
33	Parameter $carry of method Inheritance::callBack() has invalid type null.
35	`Strict comparison using === between array
39	`Argument of an invalid type array
44	`Cannot access offset (int
47	`Method Inheritance::callBack() should return array<TKey of (int

[phpstan-bot]

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

@@ @@
-PHP 8.0 – 8.2 (1 error)
+PHP 8.0 – 8.2 (2 errors)
 ==========
 
 18: Method Inheritance::inherit() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<string>.
+33: Static method Inheritance::callBack() is unused.
 
-PHP 7.1 – 7.4 (2 errors)
+PHP 7.1 – 7.4 (10 errors)
 ==========
 
 18: Method Inheritance::inherit() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<string>.
-33: Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
+33: Method Inheritance::callBack() has parameter $carry with no value type specified in iterable type array.
+33: Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
+33: PHPDoc tag @param for parameter $carry with type array<TKey of (int|string), TValues of bool|float|int|string|null>|null is not subtype of native type array|null.
+33: Parameter $carry of method Inheritance::callBack() has invalid type null.
+33: Static method Inheritance::callBack() is unused.
+35: Strict comparison using === between array|null and null will always evaluate to false.
+39: Argument of an invalid type array|null supplied for foreach, only iterables are supported.
+44: Cannot access offset (int|string) on array|null.
+47: Method Inheritance::callBack() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array|null.

Full report

PHP 8.0 – 8.2 (2 errors)

Line	Error
18	`Method Inheritance::inherit() should return array<TKey of (int
33	Static method Inheritance::callBack() is unused.

PHP 7.1 – 7.4 (10 errors)

Line	Error
18	`Method Inheritance::inherit() should return array<TKey of (int
33	Method Inheritance::callBack() has parameter $carry with no value type specified in iterable type array.
33	Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
33	`PHPDoc tag @param for parameter $carry with type array<TKey of (int
33	Parameter $carry of method Inheritance::callBack() has invalid type null.
33	Static method Inheritance::callBack() is unused.
35	`Strict comparison using === between array
39	`Argument of an invalid type array
44	`Cannot access offset (int
47	`Method Inheritance::callBack() should return array<TKey of (int

[phpstan-bot]

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

@@ @@
 
 18: Method Inheritance::inherit() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<string>.
 
-PHP 7.1 – 7.4 (2 errors)
+PHP 7.1 – 7.4 (8 errors)
 ==========
 
 18: Method Inheritance::inherit() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<string>.
-33: Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
+33: Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
+33: PHPDoc tag @param for parameter $carry with type array<TKey of (int|string), TValues of bool|float|int|string|null>|null is not subtype of native type array|null.
+33: Parameter $carry of method Inheritance::callBack() has invalid type null.
+35: Strict comparison using === between array<TKey of (int|string), TValues of bool|float|int|string|null>|null and null will always evaluate to false.
+39: Argument of an invalid type array<TKey of (int|string), TValues of bool|float|int|string|null>|null supplied for foreach, only iterables are supported.
+44: Cannot access offset TKey of (int|string) on array<TKey of (int|string), TValues of bool|float|int|string|null>|null.
+47: Method Inheritance::callBack() should return array<TKey of (int|string), TValues of bool|float|int|string|null> but returns array<TKey of (int|string), TValues of bool|float|int|string|null>|null.

Full report

PHP 8.0 – 8.2 (1 error)

Line	Error
18	`Method Inheritance::inherit() should return array<TKey of (int

PHP 7.1 – 7.4 (8 errors)

Line	Error
18	`Method Inheritance::inherit() should return array<TKey of (int
33	Method Inheritance::callBack() uses native union types but they're supported only on PHP 8.0 and later.
33	`PHPDoc tag @param for parameter $carry with type array<TKey of (int
33	Parameter $carry of method Inheritance::callBack() has invalid type null.
35	`Strict comparison using === between array<TKey of (int
39	`Argument of an invalid type array<TKey of (int
44	`Cannot access offset TKey of (int
47	`Method Inheritance::callBack() should return array<TKey of (int