trait-stringclass-string narrowed to the name of a trait. Traits are the odd member
of the family: the name exists at compile time and ::class resolves it, but
it denotes nothing instantiable, so an analyzer that checks "is this a known
class" rather than "is this a known trait" lets an ordinary class name
through.
References:
- PHPStan TypeNodeResolver trait-string resolves to ClassStringType| Analyzer | Version | Result | Diagnostics |
|---|---|---|---|
| phan | 6.0.10Phan 6.0.10 php-ast version 1.1.3 PHP version used to run Phan: 8.5.11 | Unrecognized | phpdoc_advanced_fallback_trait_string.php:30: Saw a token Phan may have failed to parse after '* @return trait-string': after trait, saw '-' [PhanUnextractableAnnotationSuffix] phpdoc_advanced_fallback_trait_string.php:32: Return type of returnsTraitString() is undeclared type \Conformance\Tests\PhpdocAdvancedFallbackTraitString\trait [PhanUndeclaredTypeReturnType] phpdoc_advanced_fallback_trait_string.php:34: Returning SomeTrait::class of type string but returnsTraitString() is declared to return \Conformance\Tests\PhpdocAdvancedFallbackTraitString\trait (no real type) (the inferred real return type has nothing in common with the declared phpdoc return type) [PhanTypeMismatchReturnProbablyReal] phpdoc_advanced_fallback_trait_string.php:42: Saw possibly unextractable annotation for a fragment of comment '* @param trait-string $value': after trait, did not see an element name (will guess based on comment order) [PhanUnextractableAnnotationElementName] phpdoc_advanced_fallback_trait_string.php:42: Saw a token Phan may have failed to parse after '* @param trait-string $value': after trait, saw '-' [PhanUnextractableAnnotationSuffix] phpdoc_advanced_fallback_trait_string.php:44: Parameter $value has undeclared type \Conformance\Tests\PhpdocAdvancedFallbackTraitString\trait [PhanUndeclaredTypeParameter] phpdoc_advanced_fallback_trait_string.php:49: Argument 1 ($value) is returnsTraitString() of type \Conformance\Tests\PhpdocAdvancedFallbackTraitString\trait but \Conformance\Tests\PhpdocAdvancedFallbackTraitString\acceptsString() takes string defined at /Users/megurine/repo/php/php-typing-conformance/conformance/tests/phpdoc_advanced_fallback_trait_string.php:37 [PhanTypeMismatchArgument] phpdoc_advanced_fallback_trait_string.php:52: Argument 1 ($value) is SomeTrait::class of type string but \Conformance\Tests\PhpdocAdvancedFallbackTraitString\acceptsTraitString() takes \Conformance\Tests\PhpdocAdvancedFallbackTraitString\trait (no real type) defined at /Users/megurine/repo/php/php-typing-conformance/conformance/tests/phpdoc_advanced_fallback_trait_string.php:44 (the inferred real argument type has nothing in common with the parameter's phpdoc type) [PhanTypeMismatchArgumentProbablyReal] phpdoc_advanced_fallback_trait_string.php:55: Argument 1 ($value) is SomeClass::class of type string but \Conformance\Tests\PhpdocAdvancedFallbackTraitString\acceptsTraitString() takes \Conformance\Tests\PhpdocAdvancedFallbackTraitString\trait (no real type) defined at /Users/megurine/repo/php/php-typing-conformance/conformance/tests/phpdoc_advanced_fallback_trait_string.php:44 (the inferred real argument type has nothing in common with the parameter's phpdoc type) [PhanTypeMismatchArgumentProbablyReal]
Expectation diffLine 34: Expected valid value to be accepted, got ["Returning SomeTrait::class of type string but returnsTraitString() is declared to return \\Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\trait (no real type) (the inferred real return type has nothing in common with the declared phpdoc return type) [PhanTypeMismatchReturnProbablyReal]"] Line 49: Expected valid value to be accepted, got ["Argument 1 ($value) is returnsTraitString() of type \\Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\trait but \\Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\acceptsString() takes string defined at /Users/megurine/repo/php/php-typing-conformance/conformance/tests/phpdoc_advanced_fallback_trait_string.php:37 [PhanTypeMismatchArgument]"] Line 52: Expected valid value to be accepted, got ["Argument 1 ($value) is SomeTrait::class of type string but \\Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\acceptsTraitString() takes \\Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\trait (no real type) defined at /Users/megurine/repo/php/php-typing-conformance/conformance/tests/phpdoc_advanced_fallback_trait_string.php:44 (the inferred real argument type has nothing in common with the parameter's phpdoc type) [PhanTypeMismatchArgumentProbablyReal]"] |
| phpstan | 2.3.1PHPStan - PHP Static Analysis Tool 2.3.1 | Not enforced | No diagnostics reported.
|
| psalm | 6.20.0Psalm 6.20.0@804f03c0c183d149fcd4b8c7c0c9b3fbf836d34c next: 7.0.0-rc2 |
Unrecognized (pzoom≠) | phpdoc_advanced_fallback_trait_string.php:30: The declared return type 'trait-string' for Conformance\Tests\PhpdocAdvancedFallbackTraitString\returnsTraitString is incorrect, got 'Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeTrait::class' [InvalidReturnType] phpdoc_advanced_fallback_trait_string.php:34: The inferred type 'Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeTrait::class' does not match the declared return type 'trait-string' for Conformance\Tests\PhpdocAdvancedFallbackTraitString\returnsTraitString [InvalidReturnStatement] phpdoc_advanced_fallback_trait_string.php:52: Argument 1 of Conformance\Tests\PhpdocAdvancedFallbackTraitString\acceptsTraitString expects trait-string, but Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeTrait::class provided [InvalidArgument] phpdoc_advanced_fallback_trait_string.php:55: Argument 1 of Conformance\Tests\PhpdocAdvancedFallbackTraitString\acceptsTraitString expects trait-string, but Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeClass::class provided [InvalidArgument] pzoom (Psalm port)No diagnostics from pzoom.
Expectation diffLine 34: Expected valid value to be accepted, got ["The inferred type 'Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\SomeTrait::class' does not match the declared return type 'trait-string' for Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\returnsTraitString [InvalidReturnStatement]"] Line 52: Expected valid value to be accepted, got ["Argument 1 of Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\acceptsTraitString expects trait-string, but Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\SomeTrait::class provided [InvalidArgument]"] |
| mago | 1.57.0mago 1.57.0 | Widened to class-string | No diagnostics reported.
|
| mir | 0.87.0mir 0.87.0 | Incidental (1/1) | phpdoc_advanced_fallback_trait_string.php:34: InvalidReturnType: Return type 'class-string<Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeTrait>' is not compatible with declared 'trait-string' [MIR0200] phpdoc_advanced_fallback_trait_string.php:52: InvalidArgument: Argument $value of acceptsTraitString() expects 'trait-string', got 'class-string<Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeTrait>' [MIR0201] phpdoc_advanced_fallback_trait_string.php:55: InvalidArgument: Argument $value of acceptsTraitString() expects 'trait-string', got 'class-string<Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeClass>' [MIR0201]
Expectation diffLine 34: Expected valid value to be accepted, got ["InvalidReturnType: Return type 'class-string<Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\SomeTrait>' is not compatible with declared 'trait-string' [MIR0200]"] Line 52: Expected valid value to be accepted, got ["InvalidArgument: Argument $value of acceptsTraitString() expects 'trait-string', got 'class-string<Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\SomeTrait>' [MIR0201]"] |
| phpantom | 0.11.1phpantom_lsp 0.11.1 | Not enforced | No diagnostics reported.
|
| intelephense | 1.18.5intelephense 1.18.5 | Widened to class-string | No diagnostics reported.
|
| phpactor | 2026.10.07.0Phpactor 2026.10.07.0 | Not enforced | No diagnostics reported.
|
| phpy | 1.0.19409phpy 1.0.19409 | Not enforced | No diagnostics reported.
|
| qodana | 262.10968.76PhpStorm 262.10968.76 | Widened to string | No diagnostics reported.
Notes: Checked as plain `string`: a wrong type is reported as "Expected parameter of type 'string'", and a class name passes, exactly as for `@param string`. Quick Documentation still shows `trait-string`, so the spelling is recognised and only the refinement is dropped. Unlike `class-string`, which it keeps as a type of its own, PhpStorm checks `trait-string` as a plain string. |
| 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.
|
| steins | 0.1.8steins 0.1.8 (2026-09-21 revision 76306a9) | Widened to string | No diagnostics reported.
Notes: `trait-string` lowers to `ContractTy::StrOpaque` (ADR-0038) like the rest of the `*-string` family, so Steins never checks that the string names a trait specifically — it accepts any string. |
| phpstan-strict | 2.3.1PHPStan - PHP Static Analysis Tool 2.3.1 | Not enforced | No diagnostics reported.
|
| psalm-next | 7.0.0-rc2Psalm 7.0.0-rc2@20339e3fe5b8d03bcd8061030eb2a83ad50e5783 | Unrecognized | phpdoc_advanced_fallback_trait_string.php:30: The declared return type 'trait-string' for Conformance\Tests\PhpdocAdvancedFallbackTraitString\returnsTraitString is incorrect, got 'Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeTrait::class' [InvalidReturnType] phpdoc_advanced_fallback_trait_string.php:34: The inferred type 'Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeTrait::class' does not match the declared return type 'trait-string' for Conformance\Tests\PhpdocAdvancedFallbackTraitString\returnsTraitString [InvalidReturnStatement] phpdoc_advanced_fallback_trait_string.php:52: Argument 1 of Conformance\Tests\PhpdocAdvancedFallbackTraitString\acceptsTraitString expects trait-string, but Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeTrait::class provided [InvalidArgument] phpdoc_advanced_fallback_trait_string.php:55: Argument 1 of Conformance\Tests\PhpdocAdvancedFallbackTraitString\acceptsTraitString expects trait-string, but Conformance\Tests\PhpdocAdvancedFallbackTraitString\SomeClass::class provided [InvalidArgument]
Expectation diffLine 34: Expected valid value to be accepted, got ["The inferred type 'Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\SomeTrait::class' does not match the declared return type 'trait-string' for Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\returnsTraitString [InvalidReturnStatement]"] Line 52: Expected valid value to be accepted, got ["Argument 1 of Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\acceptsTraitString expects trait-string, but Conformance\\Tests\\PhpdocAdvancedFallbackTraitString\\SomeTrait::class provided [InvalidArgument]"] |
<?php
declare(strict_types=1);
namespace Conformance\Tests\PhpdocAdvancedFallbackTraitString;
/**
* `trait-string`
*
* A `class-string` narrowed to the name of a trait. Traits are the odd member
* of the family: the name exists at compile time and `::class` resolves it, but
* it denotes nothing instantiable, so an analyzer that checks "is this a known
* class" rather than "is this a known trait" lets an ordinary class name
* through.
*
* References:
* - PHPStan TypeNodeResolver `trait-string` resolves to ClassStringType
*/
trait SomeTrait
{
}
final class SomeClass
{
use SomeTrait;
}
/**
* @return trait-string
*/
function returnsTraitString() // T: trait-string
{
return SomeTrait::class; // V
}
function acceptsString(string $value): void
{
}
/**
* @param trait-string $value
*/
function acceptsTraitString($value): void // T: trait-string
{
}
// A `trait-string` value always satisfies a native `string` parameter.
acceptsString(returnsTraitString()); // V
// The name of a trait satisfies the parameter.
acceptsTraitString(SomeTrait::class); // V
// The name of a class that uses it does not.
acceptsTraitString(SomeClass::class); // E?: a class-string is not a trait-string