error: call-convention mismatch: 'sx_handler' is declared with default sx convention but the target type expects callconv(.c)
  --> /Users/agra/projects/sx/examples/1104-diagnostics-callconv-mismatch-diagnostic.sx:12:42
   |
12 |     fp : (*void) -> *void callconv(.c) = sx_handler;
   |                                          ^^^^^^^^^^