Consider all possible one letter lifetimes in suggestion

Author: estebank

src/librustc_infer/infer/error_reporting/mod.rs

@@ -1742,7 +1742,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         let new_lt = generics
             .as_ref()
             .and_then(|(parent_g, g)| {
-                let possible = ["'a", "'b", "'c", "'d", "'e", "'f", "'g", "'h", "'i", "'j", "'k"];
+                let possible: Vec<_> = (b'a'..=b'z').map(|c| format!("'{}", c as char)).collect();
                 let mut lts_names = g
                     .params
                     .iter()
@@ -1758,9 +1758,9 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     );
                 }
                 let lts = lts_names.iter().map(|s| -> &str { &*s }).collect::<Vec<_>>();
-                possible.iter().filter(|&candidate| !lts.contains(&*candidate)).next().map(|s| *s)
+                possible.into_iter().find(|candidate| !lts.contains(&candidate.as_str()))
             })
-            .unwrap_or("'lt");
+            .unwrap_or("'lt".to_string());
         let add_lt_sugg = generics
             .as_ref()
             .and_then(|(_, g)| g.params.first())