Forbid constructors from returning any values

Fixes vimeo/psalm#9713

psalm-baseline.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<files psalm-version="5.x-dev@76364ab2ccde9930513b0e3cc7e1757d3d0469f1">
+<files psalm-version="5.x-dev@ba4e312594006059b0d9afb0c5ebeea649a59112">
   <file src="vendor/nikic/php-parser/lib/PhpParser/Node/Expr/ArrowFunction.php">
     <PossiblyUndefinedStringArrayOffset>
       <code><![CDATA[$subNodes['expr']]]></code>
@@ -1057,6 +1057,7 @@
   <file src="src/Psalm/Internal/Analyzer/Statements/ReturnAnalyzer.php">
     <PossiblyUndefinedIntArrayOffset>
       <code><![CDATA[$method_name]]></code>
+      <code><![CDATA[$method_name]]></code>
     </PossiblyUndefinedIntArrayOffset>
     <RiskyTruthyFalsyComparison>
       <code><![CDATA[!$context->calling_function_id]]></code>

src/Psalm/Internal/Analyzer/Statements/ReturnAnalyzer.php

@@ -257,6 +257,18 @@ final class ReturnAnalyzer
                         $statements_analyzer,
                         null,
                     );
+
+                    [, $method_name] = explode('::', $cased_method_id);
+                    if ($method_name === '__construct') {
+                        IssueBuffer::maybeAdd(
+                            new InvalidReturnStatement(
+                                'No return values are expected for ' . $cased_method_id,
+                                new CodeLocation($source, $stmt->expr),
+                            ),
+                            $statements_analyzer->getSuppressedIssues(),
+                        );
+                        return;
+                    }
                 } else {
                     $declared_return_type = $storage->return_type;
                 }

tests/ReturnTypeTest.php

@@ -1863,6 +1863,17 @@ class ReturnTypeTest extends TestCase
                 'ignored_issues' => [],
                 'php_version' => '8.1',
             ],
+            'constructorsShouldReturnVoid' => [
+                'code' => <<<'PHP'
+                    <?php
+                    class A {
+                        public function __construct() {
+                            return 5;
+                        }
+                    }
+                    PHP,
+                'error_message' => 'InvalidReturnStatement',
+            ],
         ];
     }
 }