Compiler rejects protocol compositions involving protocols with primary associated types, but only for existentials

[karwa]

Description

I wanted to write the type any Foo<Int> & Bar, where Foo is a protocol with a primary associated type and Bar is another protocol. For some reason the compiler disallows this with any but allows it with some.

For example, this function is okay:

doSomething(_: some Foo<Int> & Bar) {}

But this isn't

doSomething(_: any Foo<Int> & Bar) {}

// Error: non-protocol, non-class type 'Foo<Int>' cannot be used within a protocol-constrained type

Similarly:

// Works
typealias Baz = Foo<Int> & Bar

// Neither of these work
let _: any Foo<Int> & Bar
let _: any (Foo<Int> & Bar)

// Works
let _: any Baz

Reproduction

protocol Foo<T> {
    associatedtype T
}

protocol Bar {}

func doSomething(_: some Foo<Int> & Bar) {}
func doSomething(_: any Foo<Int> & Bar) {} // Error: non-protocol, non-class type 'Foo<Int>' cannot be used within a protocol-constrained type

Expected behavior

Expect that any and some are supported equally when it comes to the constraints they are attached to, and more specifically that any Foo<Int> & Bar is allowed.

Environment

Swift version 6.2-dev (LLVM 978186dad468cc4, Swift 2d7b7a7)
Target: x86_64-unknown-linux-gnu

Additional information

No response