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Custom @assert-if-true predicate narrowing a string to a string subtype

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

A user-defined boolean predicate annotated to narrow its argument to non-empty-string should let a following call that requires non-empty-string type-check. Analyzers diverge on whether they honor the (non-vendor-prefixed) @assert-if-true form and propagate the narrowed string subtype through the guarded branch. Source lead: Mago analyzer test reconcile_non_empty_string (crates/analyzer/tests/cases). Mago narrows and accepts the guarded call; this file records every tool's verdict on the same construct.

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 Fail

No diagnostics reported.

Expectation diff
Line 43: Expected 1 error(s)
phpstan 2.2.11PHPStan - PHP Static Analysis Tool 2.2.11 Pass reported Lv.7+ 
regressions_string_narrowing_assert_if_true.php:37: Parameter #1 $s of function Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, string given. [reported-from-level=7]
regressions_string_narrowing_assert_if_true.php:43: Parameter #1 $s of function Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, string given. [reported-from-level=7]
With strict-rules
regressions_string_narrowing_assert_if_true.php:37: Parameter #1 $s of function Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, string given.
regressions_string_narrowing_assert_if_true.php:43: Parameter #1 $s of function Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, string given.
psalm 6.16.1Psalm 6.16.1@f1f5de594dc76faf8784e02d3dc4716c91c6f6ac
next: 7.0.0-beta19		 Pass (pzoom≠) 
regressions_string_narrowing_assert_if_true.php:37: Argument 1 of Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, but parent type string provided [ArgumentTypeCoercion]
regressions_string_narrowing_assert_if_true.php:43: Argument 1 of Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, but parent type string provided [ArgumentTypeCoercion]
pzoom (Psalm port)
regressions_string_narrowing_assert_if_true.php:43: Argument 1 of takesNonEmpty expects non-empty-string, but parent type string provided [ArgumentTypeCoercion]
mago 1.47.4mago 1.47.4 Pass 
regressions_string_narrowing_assert_if_true.php:43: Possible argument type mismatch for argument #1 of `Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty`: expected `non-empty-string`, but possibly received `string`. [possibly-invalid-argument]
mir 0.72.1mir 0.72.1 Fail

No diagnostics reported.

Expectation diff
Line 43: Expected 1 error(s)
phpantom 0.10.0phpantom_lsp 0.10.0 Fail

No diagnostics reported.

Expectation diff
Line 43: Expected 1 error(s)
intelephense 1.18.5intelephense 1.18.5 Fail

No diagnostics reported.

Expectation diff
Line 43: Expected 1 error(s)
phpactor 2026.07.22.0Phpactor 2026.07.22.0 Fail

No diagnostics reported.

Expectation diff
Line 43: Expected 1 error(s)
phpy 0.2.0phpy 0.2.0 Fail

No diagnostics reported.

Expectation diff
Line 43: Expected 1 error(s)
qodana 262.9437.196Qodana 262.9437.196 Fail

No diagnostics reported.

Expectation diff
Line 43: Expected 1 error(s)
noverify 0.5.5NoVerify, version 0.5.5: built on: 2025.04.22 14:36:46 OS: r-kuchinskas arm64 Commit: 4774b82f8adc53fbef38f95e97af4b953b4d1529 Fail 
regressions_string_narrowing_assert_if_true.php:29: param $s miss matched with phpdoc type <<non-empty-string>> [funcParamTypeMissMatch]
Expectation diff
Line 43: Expected 1 error(s)
steins 0.1.6steins 0.1.6 (2026-08-25 revision c13b4c7) Fail

No diagnostics reported.

Expectation diff
Line 43: Expected 1 error(s)
phpstan-strict 2.2.11PHPStan - PHP Static Analysis Tool 2.2.11 Pass 
regressions_string_narrowing_assert_if_true.php:37: Parameter #1 $s of function Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, string given.
regressions_string_narrowing_assert_if_true.php:43: Parameter #1 $s of function Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, string given.
psalm-next 7.0.0-beta19Psalm 7.0.0-beta19@7e751c06a756fa64dc4c759c09fe4a173afcb433 Pass 
regressions_string_narrowing_assert_if_true.php:37: Argument 1 of Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, but parent type string provided [ArgumentTypeCoercion]
regressions_string_narrowing_assert_if_true.php:43: Argument 1 of Conformance\Tests\RegressionsStringNarrowingAssertIfTrue\takesNonEmpty expects non-empty-string, but parent type string provided [ArgumentTypeCoercion]

Source

<?php

declare(strict_types=1);

namespace Conformance\Tests\RegressionsStringNarrowingAssertIfTrue;

/**
 * Custom @assert-if-true predicate narrowing a string to a string subtype.
 *
 * A user-defined boolean predicate annotated to narrow its argument to `non-empty-string`
 * should let a following call that requires `non-empty-string` type-check. Analyzers
 * diverge on whether they honor the (non-vendor-prefixed) `@assert-if-true` form and
 * propagate the narrowed string subtype through the guarded branch.
 *
 * Source lead: Mago analyzer test `reconcile_non_empty_string`
 * (crates/analyzer/tests/cases). Mago narrows and accepts the guarded call; this file
 * records every tool's verdict on the same construct.
 */

/**
 * @assert-if-true non-empty-string $s
 */
function isNonEmpty(string $s): bool
{
    return $s !== '';
}

/** @param non-empty-string $s */
function takesNonEmpty(string $s): void // E<noverify>: NoVerify cannot evaluate the non-empty-string param type and flags the signature itself
{
    echo $s;
}

function caller(string $s): void
{
    if (isNonEmpty($s)) {
        takesNonEmpty($s); // E<phpstan>: does not narrow $s to non-empty-string through the bare @assert-if-true predicate, so reports argument.type // E<phpstan-strict>: same coercion under strict rules // E<psalm>: reports ArgumentTypeCoercion; parent type stays string. Mago and pzoom honor the assertion and stay clean. Phan is silent on the unguarded call too, so it never checked
    }
}

function unguarded(string $s): void
{
    takesNonEmpty($s); // E: string is not non-empty-string
}