Comparing generic types

[NSExceptional]

Right now, I need to check if a type is Swift's Array type. Array is generic though. Is there a way I can compare the root type of a generic type for equality like that?

[Azoy]

The simplest answer I can give is to compare the context descriptors (because there will only ever be 1 of them per type).

let array = reflectStruct([Int].self)!.descriptor

// Assuming someType refers to some variable containing `TypeMetadata`
guard someType.contextDescriptor.ptr == array.ptr else {
  // The outer type of someType is not an Array
  return nil
}

[Azoy]

The Equatable conformances for these descriptors are defined on the concrete type itself (vs. the base ContextDescriptor protocol) to be able to return values of ContextDescriptor. Hence the need to compare the pointers themselves vs. the type.

[NSExceptional]

Ah yes, comparing the [context]Descriptor properties is what I needed to do :) Thanks

func testArrayMetadataCheck() {
    let anyarray = reflectStruct([Any].self)!
    let intarray = reflectStruct([Int].self)!
    
    XCTAssert(anyarray.descriptor == intarray.descriptor)
}