Override variable certainty in global scope with @var

src/Analyser/NodeScopeResolver.php

@@ -73,6 +73,7 @@
 use PHPStan\Reflection\Php\DummyParameter;
 use PHPStan\Reflection\Php\PhpMethodReflection;
 use PHPStan\Reflection\ReflectionProvider;
+use PHPStan\TrinaryLogic;
 use PHPStan\Type\Accessory\NonEmptyArrayType;
 use PHPStan\Type\ArrayType;
 use PHPStan\Type\CallableType;
@@ -2457,6 +2458,10 @@ private function processStmtVarAnnotation(MutatingScope $scope, Node\Stmt $stmt,
 				continue;
 			}
 
+			if ($scope->getFunction() === null && !$scope->isInAnonymousFunction()) {
+				$certainty = TrinaryLogic::createYes();
+			}
+
 			$scope = $scope->assignVariable($name, $varTag->getType(), $certainty);
 		}
 

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -9970,6 +9970,11 @@ public function dataArrayTypehintWithoutNullInPhpDoc(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/array-typehint-without-null-in-phpdoc.php');
 	}
 
+	public function dataOverrideVariableCertaintyInRootScope(): array
+	{
+		return $this->gatherAssertTypes(__DIR__ . '/data/override-root-scope-variable.php');
+	}
+
 	/**
 	 * @dataProvider dataBug2574
 	 * @dataProvider dataBug2577
@@ -10027,6 +10032,7 @@ public function dataArrayTypehintWithoutNullInPhpDoc(): array
 	 * @dataProvider dataMixedTypehint
 	 * @dataProvider dataVariadics
 	 * @dataProvider dataArrayTypehintWithoutNullInPhpDoc
+	 * @dataProvider dataOverrideVariableCertaintyInRootScope
 	 * @param string $assertType
 	 * @param string $file
 	 * @param mixed ...$args

tests/PHPStan/Analyser/data/override-root-scope-variable.php

@@ -0,0 +1,42 @@
+<?php
+
+use PHPStan\TrinaryLogic;
+use function PHPStan\Analyser\assertVariableCertainty;
+
+assertVariableCertainty(TrinaryLogic::createMaybe(), $foo);
+
+/** @var Foo $foo */
+
+assertVariableCertainty(TrinaryLogic::createYes(), $foo);
+
+function (): void {
+	assertVariableCertainty(TrinaryLogic::createNo(), $foo);
+
+	/** @var Foo $foo */
+
+	assertVariableCertainty(TrinaryLogic::createNo(), $foo);
+};
+
+function (): void {
+	if (rand(0, 1) === 0) {
+		$foo = doFoo();
+	}
+
+	assertVariableCertainty(TrinaryLogic::createMaybe(), $foo);
+
+	/** @var Foo $foo */
+
+	assertVariableCertainty(TrinaryLogic::createMaybe(), $foo);
+};
+
+assertVariableCertainty(TrinaryLogic::createMaybe(), $bar);
+assert($bar instanceof Foo);
+assertVariableCertainty(TrinaryLogic::createYes(), $bar);
+
+function (): void {
+	assertVariableCertainty(TrinaryLogic::createNo(), $bar);
+
+	assert($bar instanceof Foo);
+
+	assertVariableCertainty(TrinaryLogic::createYes(), $bar);
+};