stderr:
main.swift:11:1: error: conditional conformance of type 'X<T>' to protocol 'D' does not imply conformance to inherited protocol 'B' extension X: D where T == Int { // Type 'X<T>' does not conform to protocol 'B' ^ main.swift:11:1: error: conditional conformance of type 'X<T>' to protocol 'D' does not imply conformance to inherited protocol 'C' extension X: D where T == Int { // Type 'X<T>' does not conform to protocol 'B' ^ main.swift:11:1: note: did you mean to explicitly state the conformance like 'extension X: C where ...'? extension X: D where T == Int { // Type 'X<T>' does not conform to protocol 'B' ^