Array unions are improperly collapsed

[gnarlyquack]

Bug report

array{a, b}|array{c, d} is improperly collapsed as array{a|c, b|d}

Code snippet that reproduces the problem

https://phpstan.org/r/2fe252ba-d874-4f42-9164-d5672993d555

Expected output

Line 10: No error
Line 30: Function do_foo() should return array(true, null)|array(null, true) but returns ....
Actually, something (else) weird seems to be going on in line 30 since the reported "actual" type doesn't seem to make any sense.

[gnarlyquack]

Actually, this seems to be an issue with array unions in general:
https://phpstan.org/r/794c728c-a1a8-4dee-8c80-42fcd9907ac8
I would expect an error on line 8 but, as can be seen on line 17, PHPStan is ok with a mixed array being returned.

I think my original message may have misemphasized the issue: the concern isn't just that the returned array type isn't deduced from the typecheck, but that an error isn't raised when an array of incorrect type is returned:
https://phpstan.org/r/9dbdde14-c59b-41db-a54b-7fdee611037a
I would expect errors on lines 15 and 19.

[ondrejmirtes]

Hi, just a heads-up - I consider this a feature request, with such complex needs you'd be much better served modeling your types as objects.

[gnarlyquack]

I would consider it, but I'm getting bit by #3034
https://phpstan.org/r/3d46f2f0-cf4a-4a48-8a19-3a990a8dd93d
https://phpstan.org/r/658abac8-0972-4537-a51e-9f4200929c1d

[phpstan-bot]

@gnarlyquack PHPStan now reports different result with your code snippet:

@@ @@
 45: Function foo\bar() never returns foo\Error<array<string>> so it can be removed from the return typehint.
-65: Function foo\bar() should return foo\Error<array<string>>|foo\Success<bool> but returns foo\Error<array<int, string>>.
+65: Function foo\bar() should return foo\Error<array<string>>|foo\Success<bool> but returns foo\Error<array(string)>.

Full report

Line	Error
45	Function foo\bar() never returns foo\Error<array<string>> so it can be removed from the return typehint.
65	`Function foo\bar() should return foo\Error<array>

[phpstan-bot]

@gnarlyquack PHPStan now reports different result with your code snippet:

@@ @@
 45: Function foo\bar() never returns foo\Error<array<int, string>> so it can be removed from the return typehint.
-65: Function foo\bar() should return foo\Error<array<int, string>>|foo\Success<bool> but returns foo\Error<array<int, string>>.
+65: Function foo\bar() should return foo\Error<array<int, string>>|foo\Success<bool> but returns foo\Error<array(string)>.

Full report

Line	Error
45	Function foo\bar() never returns foo\Error<array<int, string>> so it can be removed from the return typehint.
65	`Function foo\bar() should return foo\Error<array<int, string>>

[Seldaek]

Another example for this feature request https://phpstan.org/r/14283564-cafe-450f-a734-ab6188da40d8 - bit me while trying to type the write() function here https://github.com/Seldaek/monolog/blob/main/src/Monolog/Handler/AbstractProcessingHandler.php#L40 which accepts a record array with the addition of a formatted key.

Not a huge deal, I duplicated the record array in this one special instance, but would have been neat if it just worked :) And yes I can see the argument that records should be objects perhaps, but they've been arrays for 11+ years and there's lots of code working with that assumption.

[phpstan-bot]

@gnarlyquack After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-45: Function foo\bar() never returns foo\Error<array<string>> so it can be removed from the return typehint.
-65: Function foo\bar() should return foo\Error<array<string>>|foo\Success<bool> but returns foo\Error<array<int, string>>.
+45: Function foo\bar() never returns foo\Error<array<string>> so it can be removed from the return type.
+65: Function foo\bar() should return foo\Error<array<string>>|foo\Success<bool> but returns foo\Error<array(string)>.

Full report

Line	Error
45	Function foo\bar() never returns foo\Error<array<string>> so it can be removed from the return type.
65	`Function foo\bar() should return foo\Error<array>

[phpstan-bot]

@gnarlyquack After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-45: Function foo\bar() never returns foo\Error<array<int, string>> so it can be removed from the return typehint.
-65: Function foo\bar() should return foo\Error<array<int, string>>|foo\Success<bool> but returns foo\Error<array<int, string>>.
+45: Function foo\bar() never returns foo\Error<array<int, string>> so it can be removed from the return type.
+65: Function foo\bar() should return foo\Error<array<int, string>>|foo\Success<bool> but returns foo\Error<array(string)>.

Full report

Line	Error
45	Function foo\bar() never returns foo\Error<array<int, string>> so it can be removed from the return type.
65	`Function foo\bar() should return foo\Error<array<int, string>>

[phpstan-bot]

@gnarlyquack After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
 10: Parameter #1 $flag of function do_bar expects bool, true|null given.
-30: Function do_foo() should return array(true|null, true|null) but returns array(null, int<1, max>).
+30: Function do_foo() should return array{true|null, true|null} but returns array{null, int<1, max>}.

Full report

Line	Error
10	`Parameter #1 $flag of function do_bar expects bool, true
30	`Function do_foo() should return array{true

[phpstan-bot]

@gnarlyquack After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-45: Function foo\bar() never returns foo\Error<array<string>> so it can be removed from the return typehint.
-65: Function foo\bar() should return foo\Error<array<string>>|foo\Success<bool> but returns foo\Error<array<int, string>>.
+45: Function foo\bar() never returns foo\Error<array<string>> so it can be removed from the return type.
+65: Function foo\bar() should return foo\Error<array<string>>|foo\Success<bool> but returns foo\Error<array{string}>.

Full report

Line	Error
45	Function foo\bar() never returns foo\Error<array<string>> so it can be removed from the return type.
65	`Function foo\bar() should return foo\Error<array>

[phpstan-bot]

@gnarlyquack After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-45: Function foo\bar() never returns foo\Error<array<int, string>> so it can be removed from the return typehint.
-65: Function foo\bar() should return foo\Error<array<int, string>>|foo\Success<bool> but returns foo\Error<array<int, string>>.
+45: Function foo\bar() never returns foo\Error<array<int, string>> so it can be removed from the return type.
+65: Function foo\bar() should return foo\Error<array<int, string>>|foo\Success<bool> but returns foo\Error<array{string}>.

Full report

Line	Error
45	Function foo\bar() never returns foo\Error<array<int, string>> so it can be removed from the return type.
65	`Function foo\bar() should return foo\Error<array<int, string>>

[phpstan-bot]

@gnarlyquack After the latest push in 1.8.x, PHPStan now reports different result with your code snippet:

@@ @@
 10: Parameter #1 $flag of function do_bar expects bool, true|null given.
-30: Function do_foo() should return array(true|null, true|null) but returns array(null, int<1, max>).
+30: Function do_foo() should return array{null, true}|array{true, null} but returns array{null, int<1, max>}.

Full report

Line	Error
10	`Parameter #1 $flag of function do_bar expects bool, true
30	`Function do_foo() should return array{null, true}