Fix $var ?? null

Author: ondrejmirtes

src/Analyser/TypeSpecifier.php

@@ -763,7 +763,7 @@ public function specifyTypesInCondition(
 				);
 			}
 
-			if ((new ConstantBooleanType(false))->isSuperTypeOf($scope->getType($expr->right))->yes()) {
+			if ((new ConstantBooleanType(false))->isSuperTypeOf($scope->getType($expr->right)->toBoolean())->yes()) {
 				return $this->create(
 					$expr->left,
 					new NullType(),

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -415,6 +415,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-987.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-3677.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4215.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-10224.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4695.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-2977.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-3190.php');

tests/PHPStan/Analyser/data/bug-10224.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Bug10224;
+
+use PHPStan\TrinaryLogic;
+use function PHPStan\Testing\assertType;
+use function PHPStan\Testing\assertVariableCertainty;
+
+function foo(bool $condition): ?string
+{
+	if ($condition) {
+		$foo = 'bar';
+	}
+	if ($foo ?? null) {
+		assertVariableCertainty(TrinaryLogic::createYes(), $foo);
+		return $foo;
+	}
+	return null;
+}
+
+function bar(bool $condition, $a): ?string
+{
+	if ($condition) {
+		$foo = $a;
+	}
+	if ($foo ?? null) {
+		assertVariableCertainty(TrinaryLogic::createYes(), $foo);
+		assertType("mixed~null", $foo);
+		return $foo;
+	}
+	return null;
+}