fix setExistingOffsetValueType() for unset() use-case

Author: staabm

src/Analyser/NodeScopeResolver.php

@@ -160,13 +160,15 @@
 use PHPStan\ShouldNotHappenException;
 use PHPStan\TrinaryLogic;
 use PHPStan\Type\Accessory\AccessoryArrayListType;
+use PHPStan\Type\Accessory\HasOffsetValueType;
 use PHPStan\Type\Accessory\NonEmptyArrayType;
 use PHPStan\Type\ArrayType;
 use PHPStan\Type\ClosureType;
 use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantArrayTypeBuilder;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantIntegerType;
+use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\ErrorType;
 use PHPStan\Type\FileTypeMapper;
 use PHPStan\Type\GeneralizePrecision;
@@ -5931,7 +5933,25 @@ private function produceArrayDimFetchAssignValueToWrite(array $dimFetchStack, ar
 				&& $arrayDimFetch !== null
 				&& $scope->hasExpressionType($arrayDimFetch)->yes()
 			) {
+				$hasOffsetType = null;
+				if ($offsetType instanceof ConstantStringType || $offsetType instanceof ConstantIntegerType) {
+					$hasOffsetType = new HasOffsetValueType($offsetType, $valueToWrite);
+				}
 				$valueToWrite = $offsetValueType->setExistingOffsetValueType($offsetType, $valueToWrite);
+
+				if ($hasOffsetType !== null) {
+					$valueToWrite = TypeCombinator::intersect(
+						$valueToWrite,
+						$hasOffsetType,
+						new NonEmptyArrayType(),
+					);
+				} else {
+					$valueToWrite = TypeCombinator::intersect(
+						$valueToWrite,
+						new NonEmptyArrayType(),
+					);
+				}
+
 			} else {
 				$valueToWrite = $offsetValueType->setOffsetValueType($offsetType, $valueToWrite, $i === 0);
 			}

src/Type/ArrayType.php

@@ -356,23 +356,11 @@ public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $uni
 
 	public function setExistingOffsetValueType(Type $offsetType, Type $valueType): Type
 	{
-		if ($offsetType instanceof ConstantStringType || $offsetType instanceof ConstantIntegerType) {
-			return TypeCombinator::intersect(
-				new self(
-					TypeCombinator::union($this->keyType, $offsetType),
-					TypeCombinator::union($this->itemType, $valueType),
-				),
-				new HasOffsetValueType($offsetType, $valueType),
-				new NonEmptyArrayType(),
-			);
-		}
-
 		return TypeCombinator::intersect(
 			new self(
 				$this->keyType,
 				TypeCombinator::union($this->itemType, $valueType),
 			),
-			new NonEmptyArrayType(),
 		);
 	}