Support $this as a valid traversable parameter type

Author: alies-dev

SlevomatCodingStandard/Helpers/AnnotationTypeHelper.php

@@ -227,6 +227,10 @@ public static function containsItemsSpecificationForTraversable(
 			);
 		}
 
+		if ($typeNode instanceof ThisTypeNode) {
+			return $inTraversable;
+		}
+
 		if ($typeNode instanceof ConstTypeNode) {
 			return $inTraversable;
 		}

tests/Sniffs/TypeHints/ReturnTypeHintSniffTest.php

@@ -240,4 +240,18 @@ public function testWithNullTrueFalseErrors(): void
 		self::assertAllFixedInFile($report);
 	}
 
+	public function testWithThisInGenericsNoErrors(): void
+	{
+		$report = self::checkFile(__DIR__ . '/data/returnTypeHintWithTraversableNoErrors.php', [
+			'enableObjectTypeHint' => true,
+			'enableMixedTypeHint' => true,
+			'enableUnionTypeHint' => false,
+			'enableIntersectionTypeHint' => false,
+			'enableNeverTypeHint' => false,
+			'enableStandaloneNullTrueFalseTypeHints' => false,
+			'traversableTypeHints' => ['Generic'],
+		]);
+		self::assertNoSniffErrorInFile($report);
+	}
+
 }

tests/Sniffs/TypeHints/data/returnTypeHintWithTraversableNoErrors.php

@@ -0,0 +1,51 @@
+<?php // lint >= 8.0
+
+namespace FooNamespace;
+
+/**
+ * @template T
+ * @template U
+ */
+class Generic
+{
+}
+
+class Bar
+{
+}
+
+class Whatever
+{
+
+    /**
+     * @return Generic<Bar, $this>
+     */
+    public function withThisTemplateType(): Generic
+    {
+        return new Generic();
+    }
+
+    /**
+     * @return Generic<Bar, self>
+     */
+    public function withSelfTemplateType(): Generic
+    {
+        return new Generic();
+    }
+
+    /**
+     * @return Generic<Bar, static>
+     */
+    public function withStaticTemplateType(): Generic
+    {
+        return new Generic();
+    }
+
+    /**
+     * @return Generic<$this, Bar>
+     */
+    public function withThisAsFirstParam(): Generic
+    {
+        return new Generic();
+    }
+}