[swift-evolution] Tuple subtype problem

[Cao Jiannan]

Another problem about sub-typing system in Swift is tuple.

Why tuple does not support sub-typing feature?

for example:

class A{

}

class B:A {

}

let tupleB:(B,B) = (B(),B())
let tupleA:(A,A) = tupleB


This should be allowed in Swift. But a compiler typing-check error.

Thanks!


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