False-positive TypeDoesNotContainType while using conditional type for return

[MaSpeng]

Description

While trying to use a conditional type for a method return value based on the cases of an UnitEnum/BackendEnum, a TypeDoesNotContainType issue arises indicating that the value of parameter with the enum type could never be one of the enum cases.

The issue exists for me while using UnitEnum, BackedEnum<int>, and BackendEnum<string>.

Psalm Snippets

UnitEnum: https://psalm.dev/r/3a92e4a91f
BackedEnum (int): https://psalm.dev/r/cd28e96568
BackedEnum (string): https://psalm.dev/r/4c57a77aa8

PHPStan Snipppets

UnitEnum: https://phpstan.org/r/667b3feb-6a7e-4444-8666-64b37759c0d4
BackedEnum (int): https://phpstan.org/r/01028541-f166-4c1c-9ad1-f6c937fccb7f
BackedEnum (string): https://phpstan.org/r/04041665-afd1-4ebe-9b9b-5ed4725895ff

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/3a92e4a91f

<?php

enum Enum {
    case First;
    
    case Second;
	
	case Third;
}

class FirstId {}

class SecondId {}

class Test {
    /**
     * @return (
     *     $enum is Enum::First
     *         ? \Generator<FirstId>
     *         : (
     *             $enum is Enum::Second
     *             ? \Generator<SecondId>
     *             : never
     *     )
     * )
     **/
    public static function method(Enum $enum): \Generator
    {
        match ($enum) {
            Enum::First => yield new FirstId(),
            Enum::Second => yield new SecondId(),
            default => throw new \LogicException(),
        };
    }
}

/** @psalm-trace $firstIdGenerator **/
$firstIdGenerator = Test::method(Enum::First); // expected type is "Generator<mixed, FirstId, mixed, mixed>" got "Generator<mixed, FirstId, mixed, mixed>"

/** @psalm-trace $secondIdGenerator **/
$secondIdGenerator = Test::method(Enum::Second); // expected type is "Generator<mixed, SecondId, mixed, mixed>" got "Generator<mixed, FirstId, mixed, mixed>"

/** @psalm-trace $never **/
$never = Test::method(Enum::Third); // expected type is "never" got "Generator<mixed, FirstId, mixed, mixed>"

Psalm output (using commit 33b553e):

INFO: Trace - 38:1 - $firstIdGenerator: Generator<mixed, FirstId, mixed, mixed>

INFO: Trace - 41:1 - $secondIdGenerator: Generator<mixed, FirstId, mixed, mixed>

INFO: Trace - 44:1 - $never: Generator<mixed, FirstId, mixed, mixed>

ERROR: TypeDoesNotContainType - 30:13 - Type TGeneratedFromParam0:fn-test::method as Enum for $enum is never =enum(Enum::First)

ERROR: TypeDoesNotContainType - 31:13 - Type TGeneratedFromParam0:fn-test::method as Enum for $enum is never =enum(Enum::Second)

https://psalm.dev/r/cd28e96568

<?php

enum Enum: int {
    case First = 1;
    
    case Second = 2;
	
	case Third = 3;
}

class FirstId {}

class SecondId {}

class Test {
    /**
     * @param Enum $enum
     *
     * @return (
     *     $enum is Enum::First
     *         ? \Generator<FirstId>
     *         : (
     *             $enum is Enum::Second
     *             ? \Generator<SecondId>
     *             : never
     *     )
     * )
     **/
    public static function method(Enum $enum): \Generator
    {
        match ($enum) {
            Enum::First => yield new FirstId(),
            Enum::Second => yield new SecondId(),
            default => throw new \LogicException(),
        };
    }
}

/** @psalm-trace $firstIdGenerator **/
$firstIdGenerator = Test::method(Enum::First); // expected type is "Generator<mixed, FirstId, mixed, mixed>" got "Generator<mixed, FirstId, mixed, mixed>"

/** @psalm-trace $secondIdGenerator **/
$secondIdGenerator = Test::method(Enum::Second); // expected type is "Generator<mixed, SecondId, mixed, mixed>" got "Generator<mixed, FirstId, mixed, mixed>"

/** @psalm-trace $never **/
$never = Test::method(Enum::Third); // expected type is "never" got "Generator<mixed, FirstId, mixed, mixed>"

Psalm output (using commit 33b553e):

INFO: Trace - 40:1 - $firstIdGenerator: Generator<mixed, FirstId, mixed, mixed>

INFO: Trace - 43:1 - $secondIdGenerator: Generator<mixed, FirstId, mixed, mixed>

INFO: Trace - 46:1 - $never: Generator<mixed, FirstId, mixed, mixed>

ERROR: TypeDoesNotContainType - 32:13 - Type TGeneratedFromParam0:fn-test::method as Enum for $enum is never =enum(Enum::First)

ERROR: TypeDoesNotContainType - 33:13 - Type TGeneratedFromParam0:fn-test::method as Enum for $enum is never =enum(Enum::Second)

https://psalm.dev/r/4c57a77aa8

<?php

enum Enum: string {
    case First = 'first';
    
    case Second = 'second';
	
	case Third = 'third';
}

class FirstId {}

class SecondId {}

class Test {
    /**
     * @param Enum $enum
     *
     * @return (
     *     $enum is Enum::First
     *         ? \Generator<FirstId>
     *         : (
     *             $enum is Enum::Second
     *             ? \Generator<SecondId>
     *             : never
     *     )
     * )
     **/
    public static function method(Enum $enum): \Generator
    {
        match ($enum) {
            Enum::First => yield new FirstId(),
            Enum::Second => yield new SecondId(),
            default => throw new \LogicException(),
        };
    }
}

/** @psalm-trace $firstIdGenerator **/
$firstIdGenerator = Test::method(Enum::First); // expected type is "Generator<mixed, FirstId, mixed, mixed>" got "Generator<mixed, FirstId, mixed, mixed>"

/** @psalm-trace $secondIdGenerator **/
$secondIdGenerator = Test::method(Enum::Second); // expected type is "Generator<mixed, SecondId, mixed, mixed>" got "Generator<mixed, FirstId, mixed, mixed>"

/** @psalm-trace $never **/
$never = Test::method(Enum::Third); // expected type is "never" got "Generator<mixed, FirstId, mixed, mixed>"

Psalm output (using commit 33b553e):

INFO: Trace - 40:1 - $firstIdGenerator: Generator<mixed, FirstId, mixed, mixed>

INFO: Trace - 43:1 - $secondIdGenerator: Generator<mixed, FirstId, mixed, mixed>

INFO: Trace - 46:1 - $never: Generator<mixed, FirstId, mixed, mixed>

ERROR: TypeDoesNotContainType - 32:13 - Type TGeneratedFromParam0:fn-test::method as Enum for $enum is never =enum(Enum::First)

ERROR: TypeDoesNotContainType - 33:13 - Type TGeneratedFromParam0:fn-test::method as Enum for $enum is never =enum(Enum::Second)

[weirdan]

This is partially fixed by #9286. All traces produce expected results, but TypeDoesNotContainType is still there.

[weirdan]

TypeDoesNotContainType is no longer reported, and results match those of PHPStan