Skip null type in ReturnTypeFromStrictScalarReturnExprRector as often…

… not desired (#5462)

rules-tests/TypeDeclaration/Rector/ClassMethod/ReturnTypeFromStrictScalarReturnExprRector/Fixture/skip_null_as_temporary.php.inc

@@ -0,0 +1,11 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\ReturnTypeFromStrictScalarReturnExprRector\Fixture;
+
+class SkipNullAsTemporary
+{
+    public function getValue()
+    {
+        return null;
+    }
+}

rules/CodeQuality/Rector/Switch_/SingularSwitchToIfRector.php

@@ -88,7 +88,7 @@ public function refactor(Node $node): array|If_|null
         // only default → basically unwrap
         if (! $onlyCase->cond instanceof Expr) {
             // remove default clause because it cause syntax error
-            return array_filter($onlyCase->stmts, static fn(Stmt $stmt): bool => ! $stmt instanceof Break_);
+            return array_filter($onlyCase->stmts, static fn (Stmt $stmt): bool => ! $stmt instanceof Break_);
         }
 
         $if = new If_(new Identical($node->cond, $onlyCase->cond));

rules/TypeDeclaration/Rector/ClassMethod/ReturnTypeFromStrictScalarReturnExprRector.php

@@ -10,6 +10,7 @@
 use PhpParser\Node\Stmt\Function_;
 use PhpParser\Node\UnionType;
 use PHPStan\Analyser\Scope;
+use PHPStan\Type\NullType;
 use PHPStan\Type\Type;
 use Rector\Contract\Rector\ConfigurableRectorInterface;
 use Rector\PHPStanStaticTypeMapper\Enum\TypeKind;
@@ -117,6 +118,11 @@ public function refactorWithScope(Node $node, Scope $scope): ?Node
             return null;
         }
 
+        // skip null as often placeholder value and not an only type
+        if ($scalarReturnType instanceof NullType) {
+            return null;
+        }
+
         $returnTypeNode = $this->staticTypeMapper->mapPHPStanTypeToPhpParserNode($scalarReturnType, TypeKind::RETURN);
         if (! $returnTypeNode instanceof Node) {
             return null;