[swift-evolution] Tuple subtype problem

Cao Jiannan frogcjn at 163.com
Tue Feb 16 00:47:54 CST 2016

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.


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