Fixed assert() bug

Author: ondrejmirtes

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -11,6 +11,7 @@
 use PHPStan\Analyser\TypeSpecifierContext;
 use PHPStan\Reflection\ReflectionProvider;
 use PHPStan\Type\Constant\ConstantArrayType;
+use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\MixedType;
 use PHPStan\Type\NeverType;
@@ -63,7 +64,12 @@ public function findSpecifiedType(
 			if ($node->name instanceof \PhpParser\Node\Name) {
 				$functionName = strtolower((string) $node->name);
 				if ($functionName === 'assert') {
-					return $this->findSpecifiedType($scope, $node->args[0]->value);
+					$assertValue = $scope->getType($node->args[0]->value)->toBoolean();
+					if (!$assertValue instanceof ConstantBooleanType) {
+						return null;
+					}
+
+					return $assertValue->getValue();
 				}
 				if (in_array($functionName, [
 					'class_exists',

tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php

@@ -234,10 +234,6 @@ public function testImpossibleCheckTypeFunctionCall(): void
 					'Call to function property_exists() with CheckTypeFunctionCall\Bug2221 and \'foo\' will always evaluate to true.',
 					782,
 				],
-				[
-					'Call to function assert() with bool will always evaluate to true.',
-					786,
-				],
 				[
 					'Call to function property_exists() with CheckTypeFunctionCall\Bug2221 and \'foo\' will always evaluate to true.',
 					786,
@@ -382,4 +378,11 @@ public function testBug2550(): void
 		$this->analyse([__DIR__ . '/data/bug-2550.php'], []);
 	}
 
+	public function testBug3994(): void
+	{
+		$this->checkAlwaysTrueCheckTypeFunctionCall = true;
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-3994.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-3994.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Bug3994;
+
+class HelloWorld
+{
+
+	public function split(string $str): void
+	{
+		$parts = explode(".", $str);
+		assert(count($parts) === 4);
+	}
+
+}