Narrow array key type when removing HasOffsetType via ArrayType::tryRemove

src/Type/ArrayType.php

@@ -17,6 +17,7 @@
 use PHPStan\Type\Accessory\AccessoryNonFalsyStringType;
 use PHPStan\Type\Accessory\AccessoryNumericStringType;
 use PHPStan\Type\Accessory\AccessoryUppercaseStringType;
+use PHPStan\Type\Accessory\HasOffsetType;
 use PHPStan\Type\Accessory\HasOffsetValueType;
 use PHPStan\Type\Accessory\NonEmptyArrayType;
 use PHPStan\Type\Constant\ConstantArrayType;
@@ -878,6 +879,17 @@ public function tryRemove(Type $typeToRemove): ?Type
 			return new ConstantArrayType([], []);
 		}
 
+		if ($typeToRemove instanceof HasOffsetType) {
+			return $this->unsetOffset($typeToRemove->getOffsetType());
+		}
+
+		if (
+			$typeToRemove instanceof HasOffsetValueType
+			&& $typeToRemove->getValueType()->isSuperTypeOf($this->itemType)->yes()
+		) {
+			return $this->unsetOffset($typeToRemove->getOffsetType());
+		}
+
 		return null;
 	}
 

tests/PHPStan/Analyser/nsrt/bug-9461.php

@@ -0,0 +1,91 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace Bug9461;
+
+use function array_key_exists;
+use function PHPStan\Testing\assertType;
+
+function test(): void {
+	/** @var array<0|string, mixed> */
+	$defaults = ['test', 'a' => 1];
+
+	assertType('array<0|string, mixed>', $defaults);
+	if (!array_key_exists(0, $defaults)) {
+		assertType('array<string, mixed>', $defaults);
+	} else {
+		assertType('non-empty-array<0|string, mixed>&hasOffset(0)', $defaults);
+	}
+}
+
+function testStringKey(): void {
+	/** @var array<'foo'|int, mixed> */
+	$arr = [];
+
+	if (!array_key_exists('foo', $arr)) {
+		assertType('array<int, mixed>', $arr);
+	} else {
+		assertType("non-empty-array<'foo'|int, mixed>&hasOffset('foo')", $arr);
+	}
+}
+
+function testGenericIntKey(): void {
+	/** @var array<int, mixed> */
+	$arr = [];
+
+	if (!array_key_exists(0, $arr)) {
+		assertType('array<int<min, -1>|int<1, max>, mixed>', $arr);
+	}
+}
+
+function testKeyExists(): void {
+	/** @var array<0|string, mixed> */
+	$arr = [];
+
+	if (!key_exists(0, $arr)) {
+		assertType('array<string, mixed>', $arr);
+	}
+}
+
+function testNonEmptyArray(): void {
+	/** @var non-empty-array<0|string, mixed> */
+	$arr = ['test'];
+
+	assertType('non-empty-array<0|string, mixed>', $arr);
+	if (!array_key_exists(0, $arr)) {
+		assertType('non-empty-array<string, mixed>', $arr);
+	} else {
+		assertType('non-empty-array<0|string, mixed>&hasOffset(0)', $arr);
+	}
+}
+
+function testIssetDoesNotNarrowKeyType(): void {
+	/** @var array<0|string, mixed> */
+	$arr = [];
+
+	if (!isset($arr[0])) {
+		// isset also checks for null, so !isset doesn't mean key doesn't exist
+		assertType('array<0|string, mixed>', $arr);
+	} else {
+		assertType('non-empty-array<0|string, mixed>&hasOffsetValue(0, mixed~null)', $arr);
+	}
+}
+
+/**
+ * @param array<0|string, mixed>|string $label
+ * @return array<string, mixed>
+ */
+function makeSeedFromLabel($label = []): array
+{
+	$defaults = is_array($label) ? $label : [$label];
+	assertType('array<0|string, mixed>', $defaults);
+
+	if (array_key_exists(0, $defaults)) {
+		$defaults['content'] = $defaults[0];
+		unset($defaults[0]);
+	}
+	assertType('array<string, mixed>', $defaults);
+
+	return $defaults;
+}

tests/PHPStan/Type/TypeCombinatorTest.php

@@ -6167,6 +6167,24 @@ public static function dataRemove(): array
 				IntersectionType::class,
 				'non-empty-array<string, string>&oversized-array',
 			],
+			[
+				new ArrayType(new UnionType([new ConstantIntegerType(0), new StringType()]), new MixedType()),
+				new HasOffsetValueType(new ConstantIntegerType(0), new MixedType()),
+				ArrayType::class,
+				'array<string, mixed>',
+			],
+			[
+				new ArrayType(new UnionType([new ConstantIntegerType(0), new StringType()]), new IntegerType()),
+				new HasOffsetValueType(new ConstantIntegerType(0), new IntegerType()),
+				ArrayType::class,
+				'array<string, int>',
+			],
+			[
+				new ArrayType(new UnionType([new ConstantIntegerType(0), new StringType()]), new MixedType()),
+				new HasOffsetValueType(new ConstantIntegerType(0), new StringType()),
+				ArrayType::class,
+				'array<0|string, mixed>',
+			],
 		];
 	}