Fixed variable certainty of a nonexistent variable after isset()

Author: ondrejmirtes

src/Analyser/TypeSpecifier.php

@@ -45,6 +45,7 @@
 use PHPStan\Type\TypeUtils;
 use PHPStan\Type\TypeWithClassName;
 use PHPStan\Type\UnionType;
+use function array_reverse;
 
 class TypeSpecifier
 {
@@ -572,8 +573,15 @@ public function specifyTypesInCondition(
 				throw new \PHPStan\ShouldNotHappenException();
 			}
 
+			$vars = array_reverse($vars);
+
 			$types = null;
 			foreach ($vars as $var) {
+				if ($var instanceof Expr\Variable && is_string($var->name)) {
+					if ($scope->hasVariableType($var->name)->no()) {
+						return new SpecifiedTypes([], []);
+					}
+				}
 				if ($expr instanceof Expr\Isset_) {
 					if (
 						$var instanceof ArrayDimFetch

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -10209,6 +10209,11 @@ public function dataCount(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/count-type.php');
 	}
 
+	public function dataBug3985(): array
+	{
+		return $this->gatherAssertTypes(__DIR__ . '/data/bug-3985.php');
+	}
+
 	/**
 	 * @dataProvider dataBug2574
 	 * @dataProvider dataBug2577
@@ -10293,6 +10298,7 @@ public function dataCount(): array
 	 * @dataProvider dataBug1924
 	 * @dataProvider dataExtraIntTypes
 	 * @dataProvider dataCount
+	 * @dataProvider dataBug3985
 	 * @param string $assertType
 	 * @param string $file
 	 * @param mixed ...$args

tests/PHPStan/Analyser/data/bug-3985.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Bug3985;
+
+use PHPStan\TrinaryLogic;
+use function PHPStan\Analyser\assertVariableCertainty;
+
+class Foo
+{
+	public function doFoo(array $array): void
+	{
+		foreach ($array as $val) {
+			if (isset($foo[1])) {
+				assertVariableCertainty(TrinaryLogic::createNo(), $foo);
+			}
+		}
+	}
+
+	public function doBar(): void
+	{
+		if (isset($foo[1])) {
+			assertVariableCertainty(TrinaryLogic::createNo(), $foo);
+		}
+	}
+}