Improve return type precision of filter_input with invalid first args

src/Type/Php/FilterFunctionReturnTypeHelper.php

@@ -3,6 +3,7 @@
 namespace PHPStan\Type\Php;
 
 use PhpParser\Node;
+use PHPStan\Php\PhpVersion;
 use PHPStan\Reflection\ReflectionProvider;
 use PHPStan\ShouldNotHappenException;
 use PHPStan\TrinaryLogic;
@@ -19,6 +20,7 @@
 use PHPStan\Type\IntegerRangeType;
 use PHPStan\Type\IntegerType;
 use PHPStan\Type\MixedType;
+use PHPStan\Type\NeverType;
 use PHPStan\Type\NullType;
 use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
@@ -46,7 +48,9 @@ final class FilterFunctionReturnTypeHelper
 	/** @var array<int, list<string>>|null */
 	private ?array $filterTypeOptions = null;
 
-	public function __construct(private ReflectionProvider $reflectionProvider)
+	private ?Type $supportedFilterInputTypes = null;
+
+	public function __construct(private ReflectionProvider $reflectionProvider, private PhpVersion $phpVersion)
 	{
 		$this->flagsString = new ConstantStringType('flags');
 	}
@@ -69,6 +73,33 @@ public function getOffsetValueType(Type $inputType, Type $offsetType, ?Type $fil
 			: $filteredType;
 	}
 
+	public function getInputType(Type $typeType, Type $varNameType, ?Type $filterType, ?Type $flagsType): ?Type
+	{
+		$this->supportedFilterInputTypes ??= TypeCombinator::union(
+			$this->reflectionProvider->getConstant(new Node\Name('INPUT_GET'), null)->getValueType(),
+			$this->reflectionProvider->getConstant(new Node\Name('INPUT_POST'), null)->getValueType(),
+			$this->reflectionProvider->getConstant(new Node\Name('INPUT_COOKIE'), null)->getValueType(),
+			$this->reflectionProvider->getConstant(new Node\Name('INPUT_SERVER'), null)->getValueType(),
+			$this->reflectionProvider->getConstant(new Node\Name('INPUT_ENV'), null)->getValueType(),
+		);
+
+		if (!$typeType->isInteger()->yes() || $this->supportedFilterInputTypes->isSuperTypeOf($typeType)->no()) {
+			if ($this->phpVersion->throwsTypeErrorForInternalFunctions()) {
+				return new NeverType();
+			}
+
+			// Using a null as input mimics pre PHP 8 behaviour where filter_input
+			// would return the same as if the offset does not exist
+			$inputType = new NullType();
+		} else {
+			// Pragmatical solution since global expressions are not passed through the scope for performance reasons
+			// See https://github.com/phpstan/phpstan-src/pull/2012 for details
+			$inputType = new ArrayType(new StringType(), new MixedType());
+		}
+
+		return $this->getOffsetValueType($inputType, $varNameType, $filterType, $flagsType);
+	}
+
 	public function getType(Type $inputType, ?Type $filterType, ?Type $flagsType): Type
 	{
 		$mixedType = new MixedType();

src/Type/Php/FilterInputDynamicReturnTypeExtension.php

@@ -2,23 +2,17 @@
 
 namespace PHPStan\Type\Php;
 
-use PhpParser\Node;
 use PhpParser\Node\Expr\FuncCall;
 use PHPStan\Analyser\Scope;
 use PHPStan\Reflection\FunctionReflection;
-use PHPStan\Reflection\ReflectionProvider;
-use PHPStan\Type\ArrayType;
 use PHPStan\Type\DynamicFunctionReturnTypeExtension;
-use PHPStan\Type\MixedType;
-use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
-use PHPStan\Type\TypeCombinator;
 use function count;
 
 class FilterInputDynamicReturnTypeExtension implements DynamicFunctionReturnTypeExtension
 {
 
-	public function __construct(private FilterFunctionReturnTypeHelper $filterFunctionReturnTypeHelper, private ReflectionProvider $reflectionProvider)
+	public function __construct(private FilterFunctionReturnTypeHelper $filterFunctionReturnTypeHelper)
 	{
 	}
 
@@ -33,24 +27,8 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 			return null;
 		}
 
-		$supportedTypes = TypeCombinator::union(
-			$this->reflectionProvider->getConstant(new Node\Name('INPUT_GET'), null)->getValueType(),
-			$this->reflectionProvider->getConstant(new Node\Name('INPUT_POST'), null)->getValueType(),
-			$this->reflectionProvider->getConstant(new Node\Name('INPUT_COOKIE'), null)->getValueType(),
-			$this->reflectionProvider->getConstant(new Node\Name('INPUT_SERVER'), null)->getValueType(),
-			$this->reflectionProvider->getConstant(new Node\Name('INPUT_ENV'), null)->getValueType(),
-		);
-		$typeType = $scope->getType($functionCall->getArgs()[0]->value);
-		if (!$typeType->isInteger()->yes() || $supportedTypes->isSuperTypeOf($typeType)->no()) {
-			return null;
-		}
-
-		// Pragmatical solution since global expressions are not passed through the scope for performance reasons
-		// See https://github.com/phpstan/phpstan-src/pull/2012 for details
-		$inputType = new ArrayType(new StringType(), new MixedType());
-
-		return $this->filterFunctionReturnTypeHelper->getOffsetValueType(
-			$inputType,
+		return $this->filterFunctionReturnTypeHelper->getInputType(
+			$scope->getType($functionCall->getArgs()[0]->value),
 			$scope->getType($functionCall->getArgs()[1]->value),
 			isset($functionCall->getArgs()[2]) ? $scope->getType($functionCall->getArgs()[2]->value) : null,
 			isset($functionCall->getArgs()[3]) ? $scope->getType($functionCall->getArgs()[3]->value) : null,

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -623,7 +623,13 @@ public function dataFileAsserts(): iterable
 		}
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/filesystem-functions.php');
+
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/filter-input.php');
+		if (PHP_VERSION_ID >= 80000) {
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/filter-input-php8.php');
+		} else {
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/filter-input-php7.php');
+		}
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/filter-var.php');
 
 		if (PHP_VERSION_ID >= 80100) {

tests/PHPStan/Analyser/data/filter-input-php7.php

@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+
+namespace FilterInputPhp7;
+
+use function PHPStan\Testing\assertType;
+
+class FilterInputPhp7
+{
+
+	public function invalidTypesOrVarNames($mixed): void
+	{
+		assertType('null', filter_input(-1, 'foo', FILTER_VALIDATE_INT));
+		assertType('false', filter_input(-1, 'foo', FILTER_VALIDATE_INT, FILTER_NULL_ON_FAILURE));
+	}
+
+}

tests/PHPStan/Analyser/data/filter-input-php8.php

@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+
+namespace FilterInputPhp8;
+
+use function PHPStan\Testing\assertType;
+
+class FilterInputPhp8
+{
+
+	public function invalidTypesOrVarNames($mixed): void
+	{
+		assertType('*NEVER*', filter_input(-1, 'foo', FILTER_VALIDATE_INT));
+		assertType('*NEVER*', filter_input(-1, 'foo', FILTER_VALIDATE_INT, FILTER_NULL_ON_FAILURE));
+	}
+
+}

tests/PHPStan/Analyser/data/filter-input.php

@@ -10,7 +10,6 @@ class FilterInput
 	public function invalidTypesOrVarNames($mixed): void
 	{
 		assertType('int|false|null', filter_input(INPUT_GET, $mixed, FILTER_VALIDATE_INT));
-		assertType('mixed', filter_input(-1, 'foo', FILTER_VALIDATE_INT));
 		assertType('null', filter_input(INPUT_GET, 17, FILTER_VALIDATE_INT));
 		assertType('false', filter_input(INPUT_GET, 17, FILTER_VALIDATE_INT, FILTER_NULL_ON_FAILURE));
 	}