From 47ddd3b911f5c85d8fbfc08eda530dac98f67dc9 Mon Sep 17 00:00:00 2001
From: Ondrej Mirtes <ondrej@mirtes.cz>
Date: Tue, 12 Dec 2023 10:15:15 +0100
Subject: [PATCH] Do not generalize template types in `@template-covariant`

---
 src/Analyser/MutatingScope.php                | 12 ++++----
 src/Reflection/ResolvedFunctionVariant.php    | 12 ++++----
 tests/PHPStan/Analyser/data/bug-7078.php      |  2 +-
 .../data/generics-do-not-generalize.php       | 29 +++++++++++++++++++
 4 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index 8bef830887..f992b20b86 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -5063,11 +5063,13 @@ private function exactInstantiation(New_ $node, string $className): ?Type
 						return $type->getBound();
 					}
 
-					$isArrayKey = $type->getBound()->describe(VerbosityLevel::precise()) === '(int|string)';
-					if ($newType->isScalar()->yes() && !$type->getVariance()->covariant() && $isArrayKey) {
-						$newType = $newType->generalize(GeneralizePrecision::templateArgument());
-					} elseif ($newType->isConstantValue()->yes() && (!$type->getBound()->isScalar()->yes() || $isArrayKey)) {
-						$newType = $newType->generalize(GeneralizePrecision::templateArgument());
+					if (!$type->getVariance()->covariant()) {
+						$isArrayKey = $type->getBound()->describe(VerbosityLevel::precise()) === '(int|string)';
+						if ($newType->isScalar()->yes() && $isArrayKey) {
+							$newType = $newType->generalize(GeneralizePrecision::templateArgument());
+						} elseif ($newType->isConstantValue()->yes() && (!$type->getBound()->isScalar()->yes() || $isArrayKey)) {
+							$newType = $newType->generalize(GeneralizePrecision::templateArgument());
+						}
 					}
 
 					return $newType;
diff --git a/src/Reflection/ResolvedFunctionVariant.php b/src/Reflection/ResolvedFunctionVariant.php
index cb026a8cb7..1616122192 100644
--- a/src/Reflection/ResolvedFunctionVariant.php
+++ b/src/Reflection/ResolvedFunctionVariant.php
@@ -184,11 +184,13 @@ private function resolveResolvableTemplateTypes(Type $type, TemplateTypeVariance
 					return $traverse($type);
 				}
 
-				$isArrayKey = $type->getBound()->describe(VerbosityLevel::precise()) === '(int|string)';
-				if ($newType->isScalar()->yes() && !$type->getVariance()->covariant() && $isArrayKey) {
-					$newType = $newType->generalize(GeneralizePrecision::templateArgument());
-				} elseif ($newType->isConstantValue()->yes() && (!$type->getBound()->isScalar()->yes() || $isArrayKey)) {
-					$newType = $newType->generalize(GeneralizePrecision::templateArgument());
+				if (!$type->getVariance()->covariant()) {
+					$isArrayKey = $type->getBound()->describe(VerbosityLevel::precise()) === '(int|string)';
+					if ($newType->isScalar()->yes() && $isArrayKey) {
+						$newType = $newType->generalize(GeneralizePrecision::templateArgument());
+					} elseif ($newType->isConstantValue()->yes() && (!$type->getBound()->isScalar()->yes() || $isArrayKey)) {
+						$newType = $newType->generalize(GeneralizePrecision::templateArgument());
+					}
 				}
 
 				$variance = TemplateTypeVariance::createInvariant();
diff --git a/tests/PHPStan/Analyser/data/bug-7078.php b/tests/PHPStan/Analyser/data/bug-7078.php
index 11b688fc15..5287dcc7cf 100644
--- a/tests/PHPStan/Analyser/data/bug-7078.php
+++ b/tests/PHPStan/Analyser/data/bug-7078.php
@@ -33,5 +33,5 @@ public function get(TypeDefault ...$type);
 
 function (Param $p) {
 	$result = $p->get(new TypeDefault(1), new TypeDefault('a'));
-	assertType('int|string', $result);
+	assertType('1|\'a\'', $result);
 };
diff --git a/tests/PHPStan/Analyser/data/generics-do-not-generalize.php b/tests/PHPStan/Analyser/data/generics-do-not-generalize.php
index a472a8df11..d00b8b699a 100644
--- a/tests/PHPStan/Analyser/data/generics-do-not-generalize.php
+++ b/tests/PHPStan/Analyser/data/generics-do-not-generalize.php
@@ -117,3 +117,32 @@ function (): void {
 
 	assertType('ArrayIterator<int, string>', createArrayIterator($a));
 };
+
+/** @template T */
+class FooInvariant
+{
+
+	/** @param T $p */
+	public function __construct($p)
+	{
+
+	}
+
+}
+
+/** @template-covariant T */
+class FooCovariant
+{
+
+	/** @param T $p */
+	public function __construct($p)
+	{
+
+	}
+
+}
+
+function (): void {
+	assertType('GenericsDoNotGeneralize\\FooInvariant<int>', new FooInvariant(1));
+	assertType('GenericsDoNotGeneralize\\FooCovariant<1>', new FooCovariant(1));
+};