`key-of<T>` with a class-constant operand

Group: Advanced PHPDoc types · Category: ecosystem · File: phpdoc_advanced_fallback_key_of_constant.php

The plain key-of test writes its shape out inline; here the operand is a reference to a class constant holding an array. Evaluating it needs one step more than the inline form: the constant has to be resolved to its value and the value to its keys before there is anything to take the keys *of*. A tool can support key-of<array{...}> and still not follow the reference. References: - PHPStan phpdoc-types: key-of with constant operands - Psalm utility_types.md: key-of on class constants

Analyzer results

Analyzer	Version	Result	Diagnostics
phan	6.0.7Phan 6.0.7 php-ast version 1.1.3 PHP version used to run Phan: 8.5.9	Unrecognized	phpdoc_advanced_fallback_key_of_constant.php:27: Saw a token Phan may have failed to parse after '* @return key-of<Config::MAP>': after key-of, saw '<' [PhanUnextractableAnnotationSuffix] phpdoc_advanced_fallback_key_of_constant.php:39: Saw possibly unextractable annotation for a fragment of comment '* @param key-of<Config::MAP> $key': after key-of, did not see an element name (will guess based on comment order) [PhanUnextractableAnnotationElementName] phpdoc_advanced_fallback_key_of_constant.php:39: Saw a token Phan may have failed to parse after '* @param key-of<Config::MAP> $key': after key-of, saw '<' [PhanUnextractableAnnotationSuffix] Recognition: spelling not resolved — reported on declaration line(s) 27, 39 Enforcement: 0/1 of the expected violations reported — incidental, since the spelling was not resolved
phpstan	2.2.8PHPStan - PHP Static Analysis Tool 2.2.8	Enforced reported Lv.5+	phpdoc_advanced_fallback_key_of_constant.php:53: Parameter #1 $key of function Conformance\Tests\PhpdocAdvancedFallbackKeyOfConstant\acceptsConfigKey expects 'debug'\|'verbose', 'missing' given. [identifier=argument.type] [reported-from-level=5] With strict-rules phpdoc_advanced_fallback_key_of_constant.php:53: Parameter #1 $key of function Conformance\Tests\PhpdocAdvancedFallbackKeyOfConstant\acceptsConfigKey expects 'debug'\|'verbose', 'missing' given. [identifier=argument.type] Recognition: spelling resolved Enforcement: 1/1 of the expected violations reported
psalm	6.16.1Psalm 6.16.1@f1f5de594dc76faf8784e02d3dc4716c91c6f6ac next: 7.0.0-beta19	Enforced	phpdoc_advanced_fallback_key_of_constant.php:53: Argument 1 of Conformance\Tests\PhpdocAdvancedFallbackKeyOfConstant\acceptsConfigKey expects 'debug'\|'verbose', but 'missing' provided [InvalidArgument] Recognition: spelling resolved Enforcement: 1/1 of the expected violations reported
mago	1.46.0mago 1.46.0	Enforced	phpdoc_advanced_fallback_key_of_constant.php:53: Invalid argument type for argument #1 of `Conformance\Tests\PhpdocAdvancedFallbackKeyOfConstant\acceptsConfigKey`: expected `string('debug')\|string('verbose')`, but found `string('missing')`. [invalid-argument] Recognition: spelling resolved Enforcement: 1/1 of the expected violations reported
mir	0.70.1mir 0.70.1	Not enforced	No diagnostics reported. Recognition: spelling resolved Enforcement: 0/1 of the expected violations reported
phpantom	0.9.0phpantom_lsp 0.9.0	Incidental (1/1)	phpdoc_advanced_fallback_key_of_constant.php:31: Return type string is incompatible with declared return type key-of<Config::MAP> [type_mismatch_return] phpdoc_advanced_fallback_key_of_constant.php:46: Argument 1 ($value) expects string, got key-of<Config::MAP> [type_mismatch_argument] phpdoc_advanced_fallback_key_of_constant.php:49: Argument 1 ($key) expects key-of<Config::MAP>, got 'debug' [type_mismatch_argument] phpdoc_advanced_fallback_key_of_constant.php:50: Argument 1 ($key) expects key-of<Config::MAP>, got 'verbose' [type_mismatch_argument] phpdoc_advanced_fallback_key_of_constant.php:53: Argument 1 ($key) expects key-of<Config::MAP>, got 'missing' [type_mismatch_argument] Recognition: spelling resolved Enforcement: 1/1 of the expected violations reported — incidental, since values the type admits were also rejected on line(s) 31, 46, 49, 50 Expectation diff Line 31: Expected valid value to be accepted, got ["Return type string is incompatible with declared return type key-of<Config::MAP> [type_mismatch_return]"] Line 46: Expected valid value to be accepted, got ["Argument 1 ($value) expects string, got key-of<Config::MAP> [type_mismatch_argument]"] Line 49: Expected valid value to be accepted, got ["Argument 1 ($key) expects key-of<Config::MAP>, got 'debug' [type_mismatch_argument]"] Line 50: Expected valid value to be accepted, got ["Argument 1 ($key) expects key-of<Config::MAP>, got 'verbose' [type_mismatch_argument]"]
intelephense	1.18.5intelephense 1.18.5	Not enforced	No diagnostics reported. Recognition: spelling resolved Enforcement: 0/1 of the expected violations reported
phpy	0.2.0phpy 0.2.0	Not enforced	No diagnostics reported. Recognition: spelling resolved Enforcement: 0/1 of the expected violations reported
qodana	262.8665.325Qodana 262.8665.325	Unrecognized	phpdoc_advanced_fallback_key_of_constant.php:27: Return type in PHPDoc does not match the actual return type [PhpReturnDocTypeMismatchInspection] Recognition: spelling not resolved — reported on declaration line(s) 27 Enforcement: 0/1 of the expected violations reported — incidental, since the spelling was not resolved
noverify	0.5.5NoVerify, version 0.5.5: built on: 2025.04.22 14:36:46 OS: r-kuchinskas arm64 Commit: 4774b82f8adc53fbef38f95e97af4b953b4d1529	Not enforced	No diagnostics reported. Recognition: spelling resolved Enforcement: 0/1 of the expected violations reported
steins	0.1.5steins 0.1.5 (2026-08-12 revision 39b4cc1)	Enforced	phpdoc_advanced_fallback_key_of_constant.php:53: argument "missing" to acceptsConfigKey() violates declared @param key-of<Config::MAP> $key — declared contract violation [phpdoc.param-mismatch] Recognition: spelling resolved Enforcement: 1/1 of the expected violations reported
phpstan-strict	2.2.8PHPStan - PHP Static Analysis Tool 2.2.8	Enforced	phpdoc_advanced_fallback_key_of_constant.php:53: Parameter #1 $key of function Conformance\Tests\PhpdocAdvancedFallbackKeyOfConstant\acceptsConfigKey expects 'debug'\|'verbose', 'missing' given. [identifier=argument.type] Recognition: spelling resolved Enforcement: 1/1 of the expected violations reported
psalm-next	7.0.0-beta19Psalm 7.0.0-beta19@7e751c06a756fa64dc4c759c09fe4a173afcb433	Enforced	phpdoc_advanced_fallback_key_of_constant.php:53: Argument 1 of Conformance\Tests\PhpdocAdvancedFallbackKeyOfConstant\acceptsConfigKey expects 'debug'\|'verbose', but 'missing' provided [InvalidArgument] Recognition: spelling resolved Enforcement: 1/1 of the expected violations reported

Source

<?php

declare(strict_types=1);

namespace Conformance\Tests\PhpdocAdvancedFallbackKeyOfConstant;

/**
 * `key-of<T>` with a class-constant operand
 *
 * The plain `key-of` test writes its shape out inline; here the operand is a
 * reference to a class constant holding an array. Evaluating it needs one step
 * more than the inline form: the constant has to be resolved to its value and
 * the value to its keys before there is anything to take the keys *of*. A tool
 * can support `key-of<array{...}>` and still not follow the reference.
 *
 * References:
 * - PHPStan phpdoc-types: key-of with constant operands
 * - Psalm utility_types.md: key-of on class constants
 */

final class Config
{
    public const MAP = ['debug' => false, 'verbose' => true];
}

/**
 * @return key-of<Config::MAP>
 */
function returnsConfigKey() // T: key-of<Config::MAP>
{
    return \random_int(0, 1) === 1 ? 'debug' : 'verbose'; // V
}

function acceptsString(string $value): void
{
}

/**
 * @param key-of<Config::MAP> $key
 */
function acceptsConfigKey($key): void // T: key-of<Config::MAP>
{
}

// Every key of the constant is a string.
acceptsString(returnsConfigKey()); // V

// Both keys of the constant satisfy the parameter.
acceptsConfigKey('debug'); // V
acceptsConfigKey('verbose'); // V

// A string that is not one of them does not.
acceptsConfigKey('missing'); // E?: 'missing' is not a key of Config::MAP

key-of<T> with a class-constant operand

Analyzer results

Source

`key-of<T>` with a class-constant operand