Specify types for Doctrine Collection first() method

extension.neon

@@ -305,3 +305,9 @@ services:
 		tags: [phpstan.doctrine.typeDescriptor]
 		arguments:
 			uuidTypeName: Ramsey\Uuid\Doctrine\UuidBinaryOrderedTimeType
+
+	# Doctrine Collection
+	-
+		class: PHPStan\Type\Doctrine\Collection\FirstTypeSpecifyingExtension
+		tags:
+			- phpstan.typeSpecifier.methodTypeSpecifyingExtension

src/Type/Doctrine/Collection/FirstTypeSpecifyingExtension.php

@@ -0,0 +1,75 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Doctrine\Collection;
+
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Analyser\SpecifiedTypes;
+use PHPStan\Analyser\TypeSpecifier;
+use PHPStan\Analyser\TypeSpecifierAwareExtension;
+use PHPStan\Analyser\TypeSpecifierContext;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\Constant\ConstantBooleanType;
+use PHPStan\Type\MethodTypeSpecifyingExtension;
+use PHPStan\Type\TypeCombinator;
+
+final class FirstTypeSpecifyingExtension implements MethodTypeSpecifyingExtension, TypeSpecifierAwareExtension
+{
+
+	private const COLLECTION_CLASS = 'Doctrine\Common\Collections\Collection';
+	private const IS_EMPTY_METHOD_NAME = 'isEmpty';
+	private const FIRST_METHOD_NAME = 'first';
+
+	/** @var TypeSpecifier */
+	private $typeSpecifier;
+
+	public function getClass(): string
+	{
+		return self::COLLECTION_CLASS;
+	}
+
+	public function isMethodSupported(
+		MethodReflection $methodReflection,
+		MethodCall $node,
+		TypeSpecifierContext $context
+	): bool
+	{
+		return (
+			$methodReflection->getDeclaringClass()->getName() === self::COLLECTION_CLASS
+			|| $methodReflection->getDeclaringClass()->isSubclassOf(self::COLLECTION_CLASS)
+		)
+		&& $methodReflection->getName() === self::IS_EMPTY_METHOD_NAME;
+	}
+
+	public function specifyTypes(
+		MethodReflection $methodReflection,
+		MethodCall $node,
+		Scope $scope,
+		TypeSpecifierContext $context
+	): SpecifiedTypes
+	{
+		$classReflection = $methodReflection->getDeclaringClass();
+		$methodVariants = $classReflection->getNativeMethod(self::FIRST_METHOD_NAME)->getVariants();
+
+		if ($context->truthy()) {
+			return $this->typeSpecifier->create(
+				new MethodCall($node->var, self::FIRST_METHOD_NAME),
+				new ConstantBooleanType(false),
+				$context
+			);
+		}
+
+		return $this->typeSpecifier->create(
+			new MethodCall($node->var, self::FIRST_METHOD_NAME),
+			TypeCombinator::remove(ParametersAcceptorSelector::selectSingle($methodVariants)->getReturnType(), new ConstantBooleanType(false)),
+			$context
+		);
+	}
+
+	public function setTypeSpecifier(TypeSpecifier $typeSpecifier): void
+	{
+		$this->typeSpecifier = $typeSpecifier;
+	}
+
+}