Fix phpstan/phpstan#12686: Unable to mark an anonymous function as impure (phpstan#5348)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: 3 people

src/Analyser/TypeSpecifier.php

@@ -2231,6 +2231,30 @@ private function createForExpr(
 			}
 		}
 
+		if (
+			$expr instanceof FuncCall
+			&& !$expr->name instanceof Name
+		) {
+			$nameType = $scope->getType($expr->name);
+			if ($nameType->isCallable()->yes()) {
+				$isPure = null;
+				foreach ($nameType->getCallableParametersAcceptors($scope) as $variant) {
+					$variantIsPure = $variant->isPure();
+					$isPure = $isPure === null ? $variantIsPure : $isPure->and($variantIsPure);
+				}
+
+				if ($isPure !== null) {
+					if ($isPure->no()) {
+						return new SpecifiedTypes([], []);
+					}
+
+					if (!$this->rememberPossiblyImpureFunctionValues && !$isPure->yes()) {
+						return new SpecifiedTypes([], []);
+					}
+				}
+			}
+		}
+
 		if (
 			$expr instanceof MethodCall
 			&& $expr->name instanceof Node\Identifier

tests/PHPStan/Analyser/nsrt/bug-12686.php

@@ -0,0 +1,63 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12686;
+
+use function PHPStan\Testing\assertType;
+
+/** @phpstan-impure */
+$f = function (): bool {
+	return (bool) rand(0,1);
+};
+
+if ($f()) {
+	assertType('bool', $f());
+}
+
+// Pure closure should still have narrowing
+$h = function (): bool {
+	return true;
+};
+
+if ($h()) {
+	assertType('true', $h());
+}
+
+// Multiple callable parameter acceptors (union of closures)
+// When one variant is impure, the combined result should be impure
+/** @phpstan-impure */
+$impure = function (): bool {
+	return (bool) rand(0, 1);
+};
+
+$pure = function (): bool {
+	return true;
+};
+
+if (rand(0, 1)) {
+	$g = $impure;
+} else {
+	$g = $pure;
+}
+
+if ($g()) {
+	assertType('bool', $g());
+}
+
+// Multiple callable parameter acceptors where all are pure
+$pure1 = function (): bool {
+	return true;
+};
+
+$pure2 = function (): bool {
+	return true;
+};
+
+if (rand(0, 1)) {
+	$p = $pure1;
+} else {
+	$p = $pure2;
+}
+
+if ($p()) {
+	assertType('true', $p());
+}

tests/PHPStan/Analyser/nsrt/bug-3770.php

@@ -0,0 +1,27 @@
+<?php declare(strict_types = 1);
+
+namespace Bug3770;
+
+use function PHPStan\Testing\assertType;
+
+// PHPDoc on closures should be respected for purity
+
+/** @phpstan-impure */
+$f = static function (string $input): bool {
+	return strlen($input) > rand(0, 10);
+};
+
+if ($f('hello')) {
+	// Should not narrow to true because closure is impure
+	assertType('bool', $f('hello'));
+}
+
+// Closure with @phpstan-pure should allow narrowing
+/** @phpstan-pure */
+$g = static function (string $input): bool {
+	return strlen($input) > 5;
+};
+
+if ($g('hello world')) {
+	assertType('true', $g('hello world'));
+}

tests/PHPStan/Analyser/nsrt/bug-6822.php

@@ -0,0 +1,36 @@
+<?php declare(strict_types = 1);
+
+namespace Bug6822;
+
+use function PHPStan\Testing\assertType;
+
+// Closures marked as @phpstan-impure should not have their return type narrowed
+
+/** @phpstan-impure */
+$closure = function (): bool {
+	return (bool) rand(0, 1);
+};
+
+assertType('bool', $closure());
+
+if ($closure()) {
+	assertType('bool', $closure());
+
+	if ($closure()) { // should not be reported as "always true"
+		echo 'yes';
+	}
+}
+
+// Same with an explicit impure closure assigned to a variable
+/** @phpstan-impure */
+$impureFn = function (): int {
+	return rand(0, 100);
+};
+
+if ($impureFn() > 50) {
+	assertType('int<0, 100>', $impureFn());
+
+	if ($impureFn() > 50) { // should not be reported as "always true"
+		echo 'yes';
+	}
+}

tests/PHPStan/Rules/Comparison/IfConstantConditionRuleTest.php

@@ -231,4 +231,10 @@ public function testBug4284(): void
 		]);
 	}
 
+	public function testBug6822(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/../../Analyser/nsrt/bug-6822.php'], []);
+	}
+
 }