Static analyse if date_create_from_format will fail or not

conf/config.neon

@@ -962,6 +962,11 @@ services:
 		tags:
 			- phpstan.broker.dynamicFunctionReturnTypeExtension
 
+	-
+		class: PHPStan\Type\Php\DateTimeDynamicReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicFunctionReturnTypeExtension
+
 	-
 		class: PHPStan\Type\Php\DsMapDynamicReturnTypeExtension
 		tags:

src/Type/Php/DateTimeDynamicReturnTypeExtension.php

@@ -0,0 +1,43 @@
+<?php declare(strict_types=1);
+
+namespace PHPStan\Type\Php;
+
+use DateTime;
+use DateTimeImmutable;
+use PhpParser\Node\Expr\FuncCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\Constant\ConstantBooleanType;
+use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\DynamicFunctionReturnTypeExtension;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeUtils;
+
+class DateTimeDynamicReturnTypeExtension implements DynamicFunctionReturnTypeExtension
+{
+	public function isFunctionSupported(FunctionReflection $functionReflection): bool
+	{
+		return in_array($functionReflection->getName(), ['date_create_from_format', 'date_create_immutable_from_format'], true);
+	}
+
+	public function getTypeFromFunctionCall(FunctionReflection $functionReflection, FuncCall $functionCall, Scope $scope): Type
+	{
+		$defaultReturnType = ParametersAcceptorSelector::selectSingle($functionReflection->getVariants())->getReturnType();
+
+		$format = $scope->getType($functionCall->args[0]->value);
+		$datetime = $scope->getType($functionCall->args[1]->value);
+
+		if (!$format instanceof ConstantStringType || !$datetime instanceof ConstantStringType) {
+			return $defaultReturnType;
+		}
+
+		$formatValue = TypeUtils::getConstantStrings($format)[0]->getValue();
+		$datetimeValue = TypeUtils::getConstantStrings($datetime)[0]->getValue();
+		$isValid = (DateTime::createFromFormat($formatValue, $datetimeValue) !== false);
+
+		$className = $functionReflection->getName() === 'date_create_from_format' ? DateTime::class : DateTimeImmutable::class;
+		return $isValid ? new ObjectType($className) : new ConstantBooleanType(false);
+	}
+}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -381,6 +381,8 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/type-aliases.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4650.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-2906.php');
+
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/DateTimeDynamicReturnTypes.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/DateTimeDynamicReturnTypes.php

@@ -0,0 +1,43 @@
+<?php declare(strict_types=1);
+
+namespace DateTimeDynamicReturnTypes;
+
+use DateTime;
+use DateTimeImmutable;
+use function date_create_from_format;
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+	public function createDynamic(string $format, string $datetime): void {
+		assertType('DateTime|false', date_create_from_format($format, $datetime));
+		assertType('DateTimeImmutable|false', date_create_immutable_from_format($format, $datetime));
+
+		assertType('DateTime|false', DateTime::createFromFormat($format, $datetime));
+		assertType('DateTimeImmutable|false', DateTimeImmutable::createFromFormat($format, $datetime));
+	}
+
+	public function staticInvalidFormat(): void {
+		assertType('false', date_create_from_format('Foobar', '2022-02-20'));
+		assertType('false', date_create_immutable_from_format('Foobar', '2022-02-20'));
+
+		assertType('false', DateTime::createFromFormat('Foobar', '2022-02-20'));
+		assertType('false', DateTimeImmutable::createFromFormat('Foobar', '2022-02-20'));
+	}
+
+	public function staticInvalidDatetime(): void {
+		assertType('false', date_create_from_format('Y-m-d', '2022/02/20'));
+		assertType('false', date_create_immutable_from_format('Y-m-d', '2022/02/20'));
+
+		assertType('false', DateTime::createFromFormat('Y-m-d', '2022/02/20'));
+		assertType('false', DateTimeImmutable::createFromFormat('Y-m-d', '2022/02/20'));
+	}
+
+	public function staticValidStrings(): void {
+		assertType('DateTime', date_create_from_format('Y-m-d', '2020-10-12'));
+		assertType('DateTimeImmutable', date_create_immutable_from_format('Y-m-d', '2020-10-12'));
+
+		assertType('DateTime', DateTime::createFromFormat('Y-m-d', '2020-10-12'));
+		assertType('DateTimeImmutable', DateTimeImmutable::createFromFormat('Y-m-d', '2020-10-12'));
+	}
+}