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Narrowing a backed enum by its ->value comparison

Group: Cross-analyzer regressions · Category: regression · File: regressions_backed_enum_value_narrowing.php

A backed enum's case↔value map is a bijection, so $s->value === 'H' uniquely selects Suit::Hearts, and the fall-through is Suit::Spades. The match ($s) that follows is therefore exhaustive with only the Suit::Spades arm. Analyzers diverge on whether they propagate a ->value comparison to the enum case. PHPStan narrows case identity ($s === Suit::Hearts) but not the ->value form, so it keeps the full Suit type and reports the match as non-exhaustive. Source lead: cross-tool narrowing probe (companion to the class-string case).

Analyzer results

AnalyzerVersionResultDiagnostics
phan 6.0.7Phan 6.0.7 php-ast version 1.1.3 PHP version used to run Phan: 8.5.9 Pass

No diagnostics reported.

phpstan 2.2.8PHPStan - PHP Static Analysis Tool 2.2.8 Pass reported Lv.4+ 
regressions_backed_enum_value_narrowing.php:33: Match expression does not handle remaining value: Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit::Hearts [identifier=match.unhandled] [reported-from-level=4]
With strict-rules
regressions_backed_enum_value_narrowing.php:33: Match expression does not handle remaining value: Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit::Hearts [identifier=match.unhandled]
psalm 6.16.1Psalm 6.16.1@f1f5de594dc76faf8784e02d3dc4716c91c6f6ac
next: 7.0.0-beta19		 Pass 
regressions_backed_enum_value_narrowing.php:33: This match expression is not exhaustive - consider values enum(Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit::Hearts) [UnhandledMatchCondition]
mago 1.46.0mago 1.46.0 Pass 
regressions_backed_enum_value_narrowing.php:33: Non-exhaustive `match` expression: subject of type `enum(Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit)` is not fully handled. [match-not-exhaustive]
mir 0.70.1mir 0.70.1 Pass

No diagnostics reported.

phpantom 0.9.0phpantom_lsp 0.9.0 Pass

No diagnostics reported.

intelephense 1.18.5intelephense 1.18.5 Pass

No diagnostics reported.

phpy 0.2.0phpy 0.2.0 Pass

No diagnostics reported.

qodana 262.8665.325Qodana 262.8665.325 Fail 
regressions_backed_enum_value_narrowing.php:33: 'match' expression has uncovered enum cases [PhpUncoveredEnumCasesInspection]
Expectation diff
Line 33: Unexpected errors ["'match' expression has uncovered enum cases [PhpUncoveredEnumCasesInspection]"]
noverify 0.5.5NoVerify, version 0.5.5: built on: 2025.04.22 14:36:46 OS: r-kuchinskas arm64 Commit: 4774b82f8adc53fbef38f95e97af4b953b4d1529 Pass 
regressions_backed_enum_value_narrowing.php:27: Class or interface named \Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit does not exist [undefinedClass]
regressions_backed_enum_value_narrowing.php:29: Property {\Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit}->value does not exist [undefinedProperty]
regressions_backed_enum_value_narrowing.php:34: Class constant \Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit::Spades does not exist [undefinedConstant]
steins 0.1.5steins 0.1.5 (2026-08-12 revision 39b4cc1) Pass

No diagnostics reported.

phpstan-strict 2.2.8PHPStan - PHP Static Analysis Tool 2.2.8 Pass 
regressions_backed_enum_value_narrowing.php:33: Match expression does not handle remaining value: Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit::Hearts [identifier=match.unhandled]
psalm-next 7.0.0-beta19Psalm 7.0.0-beta19@7e751c06a756fa64dc4c759c09fe4a173afcb433 Pass 
regressions_backed_enum_value_narrowing.php:33: This match expression is not exhaustive - consider values enum(Conformance\Tests\RegressionsBackedEnumValueNarrowing\Suit::Hearts) [UnhandledMatchCondition]

Source

<?php

declare(strict_types=1);

namespace Conformance\Tests\RegressionsBackedEnumValueNarrowing;

/**
 * Narrowing a backed enum by its `->value` comparison.
 *
 * A backed enum's case↔value map is a bijection, so `$s->value === 'H'` uniquely selects
 * `Suit::Hearts`, and the fall-through is `Suit::Spades`. The `match ($s)` that follows is
 * therefore exhaustive with only the `Suit::Spades` arm.
 *
 * Analyzers diverge on whether they propagate a `->value` comparison to the enum case.
 * PHPStan narrows case identity (`$s === Suit::Hearts`) but not the `->value` form, so it
 * keeps the full `Suit` type and reports the `match` as non-exhaustive.
 *
 * Source lead: cross-tool narrowing probe (companion to the class-string case).
 */

enum Suit: string
{
    case Hearts = 'H';
    case Spades = 'S';
}

function describe(Suit $s): string // E<noverify>: NoVerify 0.5.5 does not support enums and treats Suit as an undefined class
{
    if ($s->value === 'H') { // E<noverify>: enum property ->value unresolved because enums are unsupported
        return 'hearts';
    }

    return match ($s) { // E<phpstan>: $s not narrowed by ->value === 'H', so match is seen as non-exhaustive (Suit::Hearts unhandled) // E<phpstan-strict>: same // E<psalm>: UnhandledMatchCondition // E<mago>: match-not-exhaustive. Phan alone treats it as exhaustive
        Suit::Spades => 'spades', // E<noverify>: enum case constant Suit::Spades unresolved
    };
}