Add Exception code return type provider

src/Psalm/Internal/Provider/ReturnTypeProvider/ExceptionCodeReturnTypeProvider.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Psalm\Internal\Provider\ReturnTypeProvider;
+
+use Psalm\Plugin\EventHandler\Event\MethodReturnTypeProviderEvent;
+use Psalm\Type;
+
+class ExceptionCodeReturnTypeProvider implements \Psalm\Plugin\EventHandler\MethodReturnTypeProviderInterface
+{
+    public static function getClassLikeNames() : array
+    {
+        return ['Throwable'];
+    }
+
+    public static function getMethodReturnType(MethodReturnTypeProviderEvent $event): ?Type\Union
+    {
+        $method_name_lowercase = $event->getMethodNameLowercase();
+        $fqcn = $event->getCalledFqClasslikeName();
+
+        if ($method_name_lowercase !== 'getcode') {
+            return null;
+        }
+
+        if ($fqcn === 'Exception' || $fqcn === 'Throwable') {
+            return null;
+        }
+
+        if (is_a($fqcn, \PDOException::class, true)) {
+            return Type::parseString('string');
+        }
+
+        return Type::parseString('int');
+    }
+}

tests/ReturnTypeProvider/ExceptionCodeTest.php

@@ -0,0 +1,56 @@
+<?php
+
+namespace Psalm\Tests\ReturnTypeProvider;
+
+use Psalm\Tests\TestCase;
+use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
+use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
+
+class ExceptionCodeTest extends TestCase
+{
+    use ValidCodeAnalysisTestTrait;
+    use InvalidCodeAnalysisTestTrait;
+
+    public function providerValidCodeParse(): iterable
+    {
+        yield 'RuntimeException' => [
+            '<?php
+                function f(\RuntimeException $e): int {
+                    return $e->getCode()
+                }
+            ',
+        ];
+        yield 'LogicException' => [
+            '<?php
+                function f(\LogicException $e): int {
+                    return $e->getCode()
+                }
+            ',
+        ];
+        yield 'PDOException' => [
+            '<?php
+                function f(\PDOException $e): string {
+                    return $e->getCode()
+                }
+            ',
+        ];
+    }
+
+    public function providerInvalidCodeParse(): iterable
+    {
+        yield 'Exception' => [
+            '<?php
+                function f(\Exception $e): int {
+                    return $e->getCode()
+                }
+            ',
+        ];
+        yield 'Throwable' => [
+            '<?php
+                function f(\Throwable $e): int {
+                    return $e->getCode()
+                }
+            ',
+        ];
+    }
+}