Keep iterable key type and value type when subtracting from iterable

Author: ondrejmirtes

src/Type/TypeCombinator.php

@@ -11,6 +11,7 @@
 use PHPStan\Type\Constant\ConstantFloatType;
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\Generic\GenericObjectType;
 use PHPStan\Type\Generic\TemplateType;
 
 class TypeCombinator
@@ -61,13 +62,17 @@ public static function remove(Type $fromType, Type $typeToRemove): Type
 				return new ConstantBooleanType(!$typeToRemove->getValue());
 			}
 		} elseif ($fromType instanceof IterableType) {
-			$traversableType = new ObjectType(\Traversable::class);
 			$arrayType = new ArrayType(new MixedType(), new MixedType());
 			if ($typeToRemove->isSuperTypeOf($arrayType)->yes()) {
-				return $traversableType;
+				return new GenericObjectType(\Traversable::class, [
+					$fromType->getIterableKeyType(),
+					$fromType->getIterableValueType(),
+				]);
 			}
+
+			$traversableType = new ObjectType(\Traversable::class);
 			if ($typeToRemove->isSuperTypeOf($traversableType)->yes()) {
-				return $arrayType;
+				return new ArrayType($fromType->getIterableKeyType(), $fromType->getIterableValueType());
 			}
 		} elseif ($fromType instanceof IntegerRangeType) {
 			$type = $fromType->tryRemove($typeToRemove);

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -10918,6 +10918,11 @@ public function dataBugInstanceOfClassString(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/instanceof-class-string.php');
 	}
 
+	public function dataBug4498(): array
+	{
+		return $this->gatherAssertTypes(__DIR__ . '/data/bug-4498.php');
+	}
+
 	/**
 	 * @param string $file
 	 * @return array<string, mixed[]>
@@ -11163,6 +11168,7 @@ private function gatherAssertTypes(string $file): array
 	 * @dataProvider dataBug3321
 	 * @dataProvider dataBug3769
 	 * @dataProvider dataBugInstanceOfClassString
+	 * @dataProvider dataBug4498
 	 * @param string $assertType
 	 * @param string $file
 	 * @param mixed ...$args

tests/PHPStan/Analyser/data/bug-1233.php

@@ -17,7 +17,7 @@ public function toArray($value): array
 		assertType('mixed~array', $value);
 
 		if (is_iterable($value)) {
-			assertType('Traversable', $value);
+			assertType('Traversable<mixed, mixed>', $value);
 			return iterator_to_array($value);
 		}
 

tests/PHPStan/Analyser/data/bug-4498.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace Bug4498;
+
+use function PHPStan\Analyser\assertType;
+
+class Foo
+{
+
+	/**
+	 * @param iterable<TKey, TValue> $iterable
+	 *
+	 * @return iterable<TKey, TValue>
+	 *
+	 * @template TKey
+	 * @template TValue
+	 */
+	public function fcn(iterable $iterable): iterable
+	{
+		if ($iterable instanceof \Traversable) {
+			assertType('iterable<TKey (method Bug4498\Foo::fcn(), argument), TValue (method Bug4498\Foo::fcn(), argument)>&Traversable', $iterable);
+			return $iterable;
+		}
+
+		assertType('array<TKey (method Bug4498\Foo::fcn(), argument), TValue (method Bug4498\Foo::fcn(), argument)>', $iterable);
+
+		return $iterable;
+	}
+
+	/**
+	 * @param iterable<TKey, TValue> $iterable
+	 *
+	 * @return iterable<TKey, TValue>
+	 *
+	 * @template TKey
+	 * @template TValue
+	 */
+	public function bar(iterable $iterable): iterable
+	{
+		if (is_array($iterable)) {
+			assertType('array<TKey (method Bug4498\Foo::bar(), argument), TValue (method Bug4498\Foo::bar(), argument)>', $iterable);
+			return $iterable;
+		}
+
+		assertType('Traversable<TKey (method Bug4498\Foo::bar(), argument), TValue (method Bug4498\Foo::bar(), argument)>', $iterable);
+
+		return $iterable;
+	}
+
+}

tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php

@@ -1862,4 +1862,12 @@ public function testBug3321(): void
 		$this->analyse([__DIR__ . '/../../Analyser/data/bug-3321.php'], []);
 	}
 
+	public function testBug4498(): void
+	{
+		$this->checkThisOnly = false;
+		$this->checkNullables = true;
+		$this->checkUnionTypes = true;
+		$this->analyse([__DIR__ . '/../../Analyser/data/bug-4498.php'], []);
+	}
+
 }

tests/PHPStan/Type/TypeCombinatorTest.php

@@ -3176,7 +3176,7 @@ public function dataRemove(): array
 				new IterableType(new MixedType(), new MixedType()),
 				new ArrayType(new MixedType(), new MixedType()),
 				ObjectType::class,
-				'Traversable',
+				'Traversable<mixed, mixed>',
 			],
 			[
 				new IterableType(new MixedType(), new MixedType()),