swift

6a4d1a41 - Prohibit isolated conformances with Sendable(Metatype) constraints

Prohibit isolated conformances with Sendable(Metatype) constraints Within the constraint system, introduce a new kind of conformance constraint, a "nonisolated conforms-to" constraint, which can only be satisfied by nonisolated conformances. Introduce this constraint instead of the normal conforms-to constraint whenever the subject type is a type parameter that has either a `Sendable` or `SendableMetatype` constraint, i.e., when the type or its values can escape the current isolation domain.