Support refinement of tagged unions of array shapes

[arnaud-lb]

Feature request

If we have some types like

@phpstan-type Pizza   array{type: 'pizza', toppings: Topping[]}
@phpstan-type Pasta   array{type: 'pasta', salsa: Salsa}
@phpstan-type Meal    Pizza|Pasta

PHPStan could be able to determine which Meal we have after looking at the type field:

/**
 * @param Meal $meal
 */
function ($meal) {
    if ($meal['type'] === 'pizza') {
        \PHPStan\dumpType($meal); // array{type: 'pizza', toppings: Topping[]} (Pizza)
    } else {
        \PHPStan\dumpType($meal); // array{type: 'pasta', salsa: Salsa} (Pasta)
    }
}

https://phpstan.org/r/cacfda2a-94de-4bb6-8da6-2c0d36732967

Flow documentation on disjoint unions: https://flow.org/en/docs/types/unions/#toc-disjointo-object-unions

[ZebulanStanphill]

Array unions are currently collapsed improperly. See #3801.

[ondrejmirtes]

Sometimes they are, but not in this case: https://phpstan.org/r/5722f56e-2429-4bfa-9ef2-78b733286287

[Seldaek]

One additional case from #6499 reposting it here for the bot's enjoyment :P

https://phpstan.org/r/2bb784a9-284c-458f-b001-5914ca6f2a70

[ondrejmirtes]

Another example from @simPod https://phpstan.org/r/2ab591eb-3a1c-434e-9c96-c46b8ef53efb

[ondrejmirtes]

See #7666

[phpstan-bot]

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

@@ @@
-18: Dumped type: array{type: 'pizza', salsa: string}|array{type: 'pizza', toppings: array<string>}
-20: Dumped type: array{type: 'pasta', salsa: string}|array{type: 'pasta', toppings: array<string>}
+18: Dumped type: array{type: 'pizza', toppings: array<string>}
+20: Dumped type: array{type: 'pasta', salsa: string}

Full report

Line	Error
18	Dumped type: array{type: 'pizza', toppings: array<string>}
20	Dumped type: array{type: 'pasta', salsa: string}

[phpstan-bot]

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

@@ @@
 17: Dumped type: array{type: 'pasta', salsa: string}|array{type: 'pizza', toppings: array<string>}
-19: Dumped type: array{type: 'pizza', salsa: string}|array{type: 'pizza', toppings: array<string>}
-21: Dumped type: array{type: 'pasta', salsa: string}|array{type: 'pasta', toppings: array<string>}
+19: Dumped type: array{type: 'pizza', toppings: array<string>}
+21: Dumped type: array{type: 'pasta', salsa: string}

Full report

Line	Error
17	`Dumped type: array{type: 'pasta', salsa: string}
19	Dumped type: array{type: 'pizza', toppings: array<string>}
21	Dumped type: array{type: 'pasta', salsa: string}

[github-actions]

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