typechecker regression when calling protocol requirement through an existential of a refining protocol

[tayloraswift]

Description

this code (the function f) type-checked on 6.0.2, but not on 6.1.1.

g and h are similar functions that typecheck successfully on both compilers.

the bug appears to be present in main as well.

Reproduction

public protocol CacheBase<Object, ObjectEntry>: Sendable {
    associatedtype ObjectEntry: Identifiable<Object.ID>
    associatedtype Object: Identifiable

    subscript(_: Object.ID) -> ObjectEntry? { get }
}
public protocol StoredPropertiesCache<ObjectEntry>: CacheBase
    where ObjectEntry: StoredPropertyMetadataAccessible, ObjectEntry.Object == Object {
}
public protocol StoredPropertyMetadataAccessible<Object>: Identifiable, Equatable {
    associatedtype Object: Identifiable where Object.ID == ID
}


struct InstrumentIdentifier: Hashable, Sendable {
}
struct Instrument: Identifiable, Sendable {
    typealias ID = InstrumentIdentifier
    var id: ID
}

struct MarketDataConfiguration: StoredPropertyMetadataAccessible {
    typealias Object = Instrument

    var id: InstrumentIdentifier
}


func f(
    id: InstrumentIdentifier,
    _ cache: any StoredPropertiesCache<MarketDataConfiguration>
) async {
    let _: MarketDataConfiguration? = cache[id]
// Type of expression is ambiguous without a type annotation
}
func g(
    id: InstrumentIdentifier,
    _ cache: any CacheBase<MarketDataConfiguration, MarketDataConfiguration>
) async {
    let _: MarketDataConfiguration? = cache[id]
}
func h(
    id: InstrumentIdentifier,
    _ cache: some StoredPropertiesCache<MarketDataConfiguration>
) async {
    let _: MarketDataConfiguration? = cache[id]
}

Expected behavior

it should compile

Environment

$ swift --version
Swift version 6.1 (swift-6.1-RELEASE)
Target: x86_64-unknown-linux-gnu

Additional information

No response

[jamieQ]

though it may not be of much solace, the example does appear to compile on more recent snapshots of the main and 6.2 branch compilers. the swiftfiddle 'nightly-main' appears to be using a build from fa86097 which was merged in late February, while the compiler explorer 'nightly' build currently points to 52f5453 (merged 3 days ago).

[AnthonyLatsis]

6.1 reduction:

protocol Id {
  associatedtype ID
}

protocol P<Id1> {
  associatedtype Id1: Id
  associatedtype Id2: Id where Id2.ID == Id1.ID

  func foo(_: Id2.ID)
}

struct MyId: Id {
  typealias ID = Int
}

func f(id: Int, cache: any P<MyId>) {
  cache.foo(id)
}