ios - Command failed due to signal: Segmentation fault: 11 while using a generic class -

i'm getting "command failed due signal: segmentation fault: 11" error:

<unknown>:0: error: unable execute command: segmentation fault: 11 <unknown>:0: error: swift frontend command failed due signal (use -v see invocation) 

i have narrowed down class:

class wsobjectdto<t> : authenticationresponsedto {      var object: t?         } 

when var object: t? commented out project compiles fine. clues i'm doing wrong here cause segmentation fault?

update: builds fine if don't inherit authenticationresponsedto.

class authenticationresponsedto : nsobject {      var tokenauthenticated = false     var wsconnectionfailed = false     var wsthrewexception = false     var jsonparserexception = false     var appversionnotsupported = false }