Skip class name case check for type hints using explicit use ... as aliases

src/Parser/UseAliasVisitor.php

@@ -0,0 +1,73 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Parser;
+
+use Override;
+use PhpParser\Node;
+use PhpParser\Node\Name;
+use PhpParser\Node\Stmt\GroupUse;
+use PhpParser\Node\Stmt\Use_;
+use PhpParser\NodeVisitorAbstract;
+use PHPStan\DependencyInjection\AutowiredService;
+use function count;
+use function strtolower;
+
+#[AutowiredService]
+final class UseAliasVisitor extends NodeVisitorAbstract
+{
+
+	public const ATTRIBUTE_NAME = 'isExplicitUseAlias';
+
+	/** @var array<string, string> alias name (original case) keyed by lowercase alias name */
+	private array $explicitAliases = [];
+
+	#[Override]
+	public function enterNode(Node $node): ?Node
+	{
+		if ($node instanceof Node\Stmt\Namespace_) {
+			$this->explicitAliases = [];
+		}
+
+		if ($node instanceof Use_ && $node->type === Use_::TYPE_NORMAL) {
+			foreach ($node->uses as $use) {
+				if ($use->alias === null) {
+					continue;
+				}
+
+				$this->explicitAliases[strtolower($use->alias->name)] = $use->alias->name;
+			}
+		}
+
+		if ($node instanceof GroupUse) {
+			foreach ($node->uses as $use) {
+				if ($use->type !== Use_::TYPE_NORMAL && $node->type !== Use_::TYPE_NORMAL) {
+					continue;
+				}
+				if ($use->alias === null) {
+					continue;
+				}
+
+				$this->explicitAliases[strtolower($use->alias->name)] = $use->alias->name;
+			}
+		}
+
+		if ($node instanceof Name) {
+			$originalName = $node->getAttribute('originalName');
+			if ($originalName instanceof Name) {
+				$originalParts = $originalName->getParts();
+				if (count($originalParts) === 1) {
+					$lowerOriginal = strtolower($originalParts[0]);
+					if (
+						isset($this->explicitAliases[$lowerOriginal])
+						&& $this->explicitAliases[$lowerOriginal] === $originalParts[0]
+					) {
+						$node->setAttribute(self::ATTRIBUTE_NAME, true);
+					}
+				}
+			}
+		}
+
+		return null;
+	}
+
+}

src/Rules/FunctionDefinitionCheck.php

@@ -19,6 +19,7 @@
 use PHPStan\DependencyInjection\AutowiredParameter;
 use PHPStan\DependencyInjection\AutowiredService;
 use PHPStan\Node\Printer\NodeTypePrinter;
+use PHPStan\Parser\UseAliasVisitor;
 use PHPStan\Php\PhpVersion;
 use PHPStan\Reflection\ExtendedParameterReflection;
 use PHPStan\Reflection\ExtendedParametersAcceptor;
@@ -852,6 +853,10 @@ private function getOriginalClassNamePairsFromTypeNode(Identifier|Name|ComplexTy
 				return [];
 			}
 
+			if ($typeNode->getAttribute(UseAliasVisitor::ATTRIBUTE_NAME) === true) {
+				return [];
+			}
+
 			$resolvedName = $typeNode->toString();
 			$originalParts = $originalName->getParts();
 			$resolvedParts = $typeNode->getParts();
@@ -866,11 +871,6 @@ private function getOriginalClassNamePairsFromTypeNode(Identifier|Name|ComplexTy
 				$originalCaseClassName = $originalName->toString();
 			}
 
-			if (strtolower($originalCaseClassName) !== strtolower($resolvedName)) {
-				// use alias, not just a case difference
-				return [];
-			}
-
 			if ($originalCaseClassName === $resolvedName) {
 				return [];
 			}

tests/PHPStan/Rules/Methods/ExistingClassesInTypehintsRuleTest.php

@@ -662,4 +662,9 @@ public function testBug14205(): void
 		$this->analyse([__DIR__ . '/data/bug-14205.php'], []);
 	}
 
+	public function testBug14617(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-14617.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Methods/data/bug-14617.php

@@ -0,0 +1,19 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14617;
+
+class MyClass {}
+
+namespace Bug14617\Consumer;
+
+use Bug14617\MyClass as myclass;
+
+function test(): myclass {
+	return new myclass();
+}
+
+class Foo {
+	public function bar(myclass $a): myclass {
+		return $a;
+	}
+}