impl

src/Analyser/TypeSpecifier.php

@@ -38,6 +38,7 @@
 use PHPStan\Type\ArrayType;
 use PHPStan\Type\BooleanType;
 use PHPStan\Type\ConditionalTypeForParameter;
+use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantArrayTypeBuilder;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantIntegerType;
@@ -665,6 +666,97 @@ public function specifyTypesInCondition(
 );
 }
 
+if (
+$issetExpr instanceof ArrayDimFetch
+&& $issetExpr->dim !== null
+) {
+$type = $scope->getType($issetExpr->var);
+if ($type instanceof MixedType) {
+return new SpecifiedTypes();
+}
+
+$dimType = $scope->getType($issetExpr->dim);
+if (!($dimType instanceof ConstantIntegerType || $dimType instanceof ConstantStringType)) {
+return new SpecifiedTypes();
+}
+
+$hasOffsetType = $type->hasOffsetValueType($dimType);
+if ($hasOffsetType->no()) {
+return new SpecifiedTypes();
+}
+
+$isset = $hasOffsetType->yes();
+$offsetType = $type->getOffsetValueType($dimType);
+$isNullable = !$offsetType->isNull()->no();
+
+$setOptionalDim = function (Type $outerType, Type $dimType): Type {
+return TypeTraverser::map($outerType, static function (Type $type, callable $traverse) use ($dimType): Type {
+if ($type instanceof UnionType || $type instanceof IntersectionType) {
+return $traverse($type);
+}
+
+if ($type instanceof ConstantArrayType) {
+$builder = ConstantArrayTypeBuilder::createFromConstantArray(
+$type->unsetOffset($dimType),
+);
+$builder->setOffsetValueType(
+$dimType,
+new NullType(),
+true,
+);
+$buildType = $builder->getArray();
+return $buildType;
+}
+
+return $type;
+});
+};
+
+$exprType = $this->create(
+$issetExpr,
+new NullType(),
+$context->negate(),
+false,
+$scope,
+$rootExpr,
+);
+if ($isset === true) {
+if ($isNullable) {
+return $exprType;
+}
+
+// array-key cannot exist in !isset()
+return $exprType->unionWith($this->create(
+$issetExpr,
+new HasOffsetType($dimType),
+$context,
+false,
+$scope,
+$rootExpr,
+));
+}
+
+if ($isNullable) {
+return $this->create(
+$issetExpr->var,
+$setOptionalDim($type, $dimType),
+$context->negate(),
+false,
+$scope,
+$rootExpr,
+);
+}
+
+return $this->create(
+$issetExpr->var,
+$type->unsetOffset($dimType),
+$context->negate(),
+false,
+$scope,
+$rootExpr,
+);
+}
+
 return new SpecifiedTypes();
 }