Offer additional note for why method with Self reference cannot be used on `any SomeType` · swiftlang/swift#76320

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compilerdiagnostics qualityexistentialsgood first issueimprovementswift 6.2type checker

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Description

Motivation

The following snippet;

protocol Base {
    associatedtype SomeID: Hashable
}

protocol Alpha: Base {
    func take(id: Self.SomeID)
}

struct Use {
    let alpha: any Alpha
    
    func test() {
        alpha.take(id: 12) // error: Member 'take' cannot be used on value of type 'any Alpha'; consider using a generic constraint instead
    }
}

is correct in rejecting the line, since we need Self.SomeID to be well typed, but we dont know what its type is via the any.

It'd be helpful if we can point out that "why" the method can't be used via a note, in a method with many parameters one can sometimes miss the Self reference.

Proposed solution

Adding a note on the offending parameter would be good

Alternatives considered

No response

Additional information