Support nested assigns

Author: staabm

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -282,11 +282,22 @@ public function findSpecifiedType(
 		$assignedInCallVars = [];
 		if ($node instanceof Expr\CallLike) {
 			foreach ($node->getArgs() as $arg) {
-				if (!$arg->value instanceof Expr\Assign) {
-					continue;
+				$expr = $arg->value;
+				while ($expr instanceof Expr\Assign) {
+					$expr = $expr->expr;
 				}
+				$assignedExpr = $expr;
+
+				$expr = $arg->value;
+				while ($expr instanceof Expr\Assign) {
+					$assignedInCallVars[] = new Expr\Assign(
+						$expr->var,
+						$assignedExpr,
+						$expr->getAttributes()
+					);
 
-				$assignedInCallVars[] = $arg->value;
+					$expr = $expr->expr;
+				}
 			}
 		}
 		foreach ($sureTypes as $sureType) {

tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php

@@ -1071,6 +1071,21 @@ public function testBug12087(): void
 		]);
 	}
 
+	#[RequiresPhp('>= 8.1')]
+	public function testBug12087c(): void
+	{
+		$tipText = 'Because the type is coming from a PHPDoc, you can turn off this check by setting <fg=cyan>treatPhpDocTypesAsCertain: false</> in your <fg=cyan>%configurationFile%</>.';
+
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-12087c.php'], [
+			[
+				'Call to function is_null() with null will always evaluate to true.',
+				17,
+				$tipText,
+			],
+		]);
+	}
+
 	public function testBug9666(): void
 	{
 		$tipText = 'Because the type is coming from a PHPDoc, you can turn off this check by setting <fg=cyan>treatPhpDocTypesAsCertain: false</> in your <fg=cyan>%configurationFile%</>.';

tests/PHPStan/Rules/Comparison/data/bug-12087c.php

@@ -9,14 +9,10 @@ enum Button: int
 	case Off = 0;
 }
 
-function doFoo() {
-	$value = 10;
-
-	is_null($foo = $value = Button::tryFrom($value));
-}
-
-function doFoo2() {
+function doFoo()
+{
+	$foo = 'abc';
 	$value = 10;
 
-	is_null($foo ??= Button::tryFrom($value));
+	is_null($value = $foo = Button::tryFrom($value));
 }