Optimize keepVoidType (#4735)

Author: staabm

src/Analyser/MutatingScope.php

@@ -2746,6 +2746,7 @@ public function getKeepVoidType(Expr $node): Type
 				(
 					!$node instanceof FuncCall
 					&& !$node instanceof MethodCall
+					&& !$node instanceof Expr\NullsafeMethodCall
 					&& !$node instanceof Expr\StaticCall
 				) || $node->isFirstClassCallable()
 			)

tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

@@ -1768,6 +1768,11 @@ public function testBug6720(): void
 		$this->analyse([__DIR__ . '/data/bug-6720.php'], []);
 	}
 
+	public function testBug6720b(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-6720b.php'], []);
+	}
+
 	public function testBug8659(): void
 	{
 		$this->analyse([__DIR__ . '/data/bug-8659.php'], []);

tests/PHPStan/Rules/Functions/data/bug-6720b.php

@@ -0,0 +1,15 @@
+<?php declare(strict_types = 1);
+
+namespace Bug6720b;
+
+class X {
+	/** @return string|void */
+	function a() {}
+
+}
+
+function b(?string $a): void {}
+
+function doFoo(?X $x):void {
+	b($x?->a());
+}