Change UnionType description if it contains TemplateUnionType

src/Type/UnionType.php

@@ -16,6 +16,7 @@
 use PHPStan\Type\Generic\TemplateType;
 use PHPStan\Type\Generic\TemplateTypeMap;
 use PHPStan\Type\Generic\TemplateTypeVariance;
+use PHPStan\Type\Generic\TemplateUnionType;
 
 /** @api */
 class UnionType implements CompoundType
@@ -153,7 +154,7 @@ public function describe(VerbosityLevel $level): string
 		$joinTypes = static function (array $types) use ($level): string {
 			$typeNames = [];
 			foreach ($types as $type) {
-				if ($type instanceof ClosureType || $type instanceof CallableType) {
+				if ($type instanceof ClosureType || $type instanceof CallableType || $type instanceof TemplateUnionType) {
 					$typeNames[] = sprintf('(%s)', $type->describe($level));
 				} elseif ($type instanceof IntersectionType) {
 					$intersectionDescription = $type->describe($level);

tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php

@@ -512,4 +512,19 @@ public function testBug3151(): void
 		$this->analyse([__DIR__ . '/data/bug-3151.php'], []);
 	}
 
+	public function testTemplateUnion(): void
+	{
+		$this->analyse([__DIR__ . '/data/return-template-union.php'], [
+			[
+				'Method ReturnTemplateUnion\Foo::doFoo2() should return T of bool|float|int|string but returns (T of bool|float|int|string)|null.',
+				25,
+			],
+			[
+				// should not be reported
+				'Method ReturnTemplateUnion\Foo::doFoo3() should return (T of bool|float|int|string)|null but returns (T of bool|float|int|string)|null.',
+				35,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Methods/data/return-template-union.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace ReturnTemplateUnion;
+
+class Foo
+{
+
+	/**
+	 * @template T of bool|string|int|float
+	 * @param T $p
+	 * @return T
+	 */
+	public function doFoo($p)
+	{
+		return $p;
+	}
+
+	/**
+	 * @template T of bool|string|int|float
+	 * @param T|null $p
+	 * @return T
+	 */
+	public function doFoo2($p)
+	{
+		return $p;
+	}
+
+	/**
+	 * @template T of bool|string|int|float
+	 * @param T|null $p
+	 * @return T|null
+	 */
+	public function doFoo3($p)
+	{
+		return $p;
+	}
+
+}

tests/PHPStan/Type/TypeCombinatorTest.php

@@ -1820,7 +1820,7 @@ public function dataUnion(): array
 					new NullType(),
 				],
 				UnionType::class,
-				'T of bool|float|int|string (function doFoo(), parameter)|null',
+				'(T of bool|float|int|string (function doFoo(), parameter))|null',
 			],
 		];
 	}