[Proposal]: IntersectionType

[norberttech]

Note

This is how example proposal might look like. Before opening a pull request, contributor should send a proposal like this one and wait for the maintainers to provide him a Definition of Done.

Describe the Proposal

In addition to all other types we should also have an intersection type, which would be almost the same as union type:

intersection<ineger&positive-integer>

API Adjustments

function type_union(Type $first, Type $second, Type ...$types) : UnionType

Are you intenting to also work on proposed change?

It's perfectly fine to just propose changes and wait for others to pick them up.

Yes

Are you interested in sponsoring this change? If you can't find time to work on given proposal but it's

time sensitive, it might be a good idea to consider sponsoring this change. Please find more details at https://flow-php.com/sponsor/

None

Integration & Dependencies

No response

[norberttech]

Note

Definition of Done is going to be prepared by one of the maintainers

Intersection Type - Definition of Done

Our goal is to add new implementation of \Flow\Types\Type.php interface.

This implementation is very similar to the existing UnionType but it will be used to represent intersection types in PHP.
The difference is that the passed value must be valid for all types in the intersection, not just one of them.

Documentation:

• Contributing Guidelines
• Project Guidelines
• Types Library
• Types Architecture

Intersection Type API

• Intersection type should implement all methods of the \Flow\Types\Type interface.
• Just like UnionType, it should also have additional public method types() : Types
• IntersectionType should be considered Native type, just like UnionType.

Development

• after each phase run composer cs:php:fix and composer test:lib:types amd composer static:analyze to ensure that your code is aligned with the coding standards and all tests are passing.
• dont try to run single test case, always run entire test suite with composer test:lib:types to ensure that all tests are passing

Implementation Phases

1. Create an empty class IntersectionType with all methods from \Flow\Types\Type interface. In this phase leave them empty.
2. Create a DSL function type_intersection() that will return an instance of IntersectionType. Get inspired by type_union() function
3. Prepare unit test first following the guidelines in the /documentation/components/libs/types/architecture.md file. Don't forget to test additional public methods.4)
4. Implement isValid() method, this phase is considered done when all tests are passing.
5. Implement assert() method, this phase is considered done when all tests are passing.
6. Implement cast() method, this phase is considered done when all tests are passing.
7. Implement types() method, this phase is considered done when all tests are passing.
8. Update the documentation in the documentation/components/libs/types.md file to include information about the new IntersectionType.