Nullsafe operator on null results in null

Author: ondrejmirtes

src/Analyser/MutatingScope.php

@@ -1702,6 +1702,9 @@ private function resolveType(string $exprString, Expr $node): Type
 
 		if ($node instanceof Expr\NullsafeMethodCall) {
 			$varType = $this->getType($node->var);
+			if ($varType->isNull()->yes()) {
+				return new NullType();
+			}
 			if (!TypeCombinator::containsNull($varType)) {
 				return $this->getType(new MethodCall($node->var, $node->name, $node->args));
 			}
@@ -1797,6 +1800,9 @@ private function resolveType(string $exprString, Expr $node): Type
 
 		if ($node instanceof Expr\NullsafePropertyFetch) {
 			$varType = $this->getType($node->var);
+			if ($varType->isNull()->yes()) {
+				return new NullType();
+			}
 			if (!TypeCombinator::containsNull($varType)) {
 				return $this->getType(new PropertyFetch($node->var, $node->name));
 			}

tests/PHPStan/Analyser/data/nullsafe.php

@@ -99,4 +99,11 @@ public function doDolor(?self $self)
 		assertType('Nullsafe\Foo|null', $self?->nullableSelf);
 	}
 
+	public function doNull(): void
+	{
+		$null = null;
+		assertType('null', $null?->foo);
+		assertType('null', $null?->doFoo());
+	}
+
 }