rust - How to fix: cannot infer an appropriate lifetime for automatic coercion -

rust - How to fix: cannot infer an appropriate lifetime for automatic coercion -

i managed run lifetime issue 1 time again seem unable resolve on own.

the compiler tells me cannot infer appropriate lifetime automatic coercion

i tried follow compilers suggestion , introduced lifetime annotations in handle_request method.

fn handle_request<'a>(&self, req: &request, res: &'a mut responsewriter) { fn set_headers(req: &request, res: &mut responsewriter) { //probably not of import illustration } match &req.request_uri { &absolutepath(ref url) => { match self.router.match_route(req.method.clone(), url.clone()) { some(route_result) => { set_headers(req, res); allow floor_req = request::request{ origin: req, params: route_result.params.clone() }; allow floor_res = response::response{ origin: res }; (route_result.route.handler)(floor_req, &mut floor_res); }, none => {} } }, _ => set_headers(req, res) } }

i had code working before wanted wrap http::server::responsewriter in own response struct. did same request before in terms of lifetimes case seems different. maybe because it's &mut instead of simple & reference.

this responsewriter struct.

use http; ///a container response pub struct response<'a> { ///the original `http::server::responsewriter` pub origin: &'a mut http::server::responsewriter<'a>, }

just incase samaritan wants compile code locally, pushed lifetime_crazyness branch here: https://github.com/cburgdorf/floor/commits/lifetime_craziness

just run make floor compile it.

ok, pulled downwards code seek , compile it. indeed, if take @ definition of response struct, see this:

pub struct response<'a> { ///the original `http::server::responsewriter` pub origin: &'a mut http::server::responsewriter<'a>, }

from compiler's perspective, definition claims lifetime of pointer http::server::responsewriter the same whatever lifetime within of http::server::responsewriter. don't see particular reason why should true, , looks compiler can't either. prepare it, need introduce lifetime parameter allow possibility lifetimes distinct:

pub struct response<'a, 'b> { ///the original `http::server::responsewriter` pub origin: &'a mut http::server::responsewriter<'b>, }

here's prepare in pr you: https://github.com/burntsushi/floor/commit/127962b9afc2779c9103c28f37e52e8d292f9ff2

rust lifetime