Function lower_handler_kind_ir 

pub fn lower_handler_kind_ir(k: &HandlerKind) -> IrHandlerKind

P6.24a: pure, unconditional HandlerKind → IrHandlerKind conversion — every field is already fully resolved at parse time, so unlike almost every other function in this module this one takes no &CheckedProgram/&TypedCommons at all and can never miss.