rustc_resolve: use Iterator combinators instead of for loops where applicable

Author: yotamofek

compiler/rustc_resolve/src/late.rs

@@ -1728,13 +1728,8 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         }
 
         let normalized_ident = ident.normalize_to_macros_2_0();
-        let mut outer_res = None;
-        for rib in lifetime_rib_iter {
-            if let Some((&outer, _)) = rib.bindings.get_key_value(&normalized_ident) {
-                outer_res = Some(outer);
-                break;
-            }
-        }
+        let outer_res = lifetime_rib_iter
+            .find_map(|rib| rib.bindings.get_key_value(&normalized_ident).map(|(&outer, _)| outer));
 
         self.emit_undeclared_lifetime_error(lifetime, outer_res);
         self.record_lifetime_res(lifetime.id, LifetimeRes::Error, LifetimeElisionCandidate::Named);
@@ -1801,23 +1796,21 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 }
                 LifetimeRibKind::AnonymousReportError => {
                     if elided {
-                        let mut suggestion = None;
-                        for rib in self.lifetime_ribs[i..].iter().rev() {
+                        let suggestion = self.lifetime_ribs[i..].iter().rev().find_map(|rib| {
                             if let LifetimeRibKind::Generics {
                                 span,
                                 kind: LifetimeBinderKind::PolyTrait | LifetimeBinderKind::WhereBound,
                                 ..
-                            } = &rib.kind
+                            } = rib.kind
                             {
-                                suggestion =
-                                    Some(errors::ElidedAnonymousLivetimeReportErrorSuggestion {
-                                        lo: span.shrink_to_lo(),
-                                        hi: lifetime.ident.span.shrink_to_hi(),
-                                    });
-                                break;
+                                Some(errors::ElidedAnonymousLivetimeReportErrorSuggestion {
+                                    lo: span.shrink_to_lo(),
+                                    hi: lifetime.ident.span.shrink_to_hi(),
+                                })
+                            } else {
+                                None
                             }
-                        }
-
+                        });
                         // are we trying to use an anonymous lifetime
                         // on a non GAT associated trait type?
                         if !self.in_func_body
@@ -2486,14 +2479,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
     /// Determine whether or not a label from the `rib_index`th label rib is reachable.
     fn is_label_valid_from_rib(&self, rib_index: usize) -> bool {
         let ribs = &self.label_ribs[rib_index + 1..];
-
-        for rib in ribs {
-            if rib.kind.is_label_barrier() {
-                return false;
-            }
-        }
-
-        true
+        ribs.iter().all(|rib| !rib.kind.is_label_barrier())
     }
 
     fn resolve_adt(&mut self, item: &'ast Item, generics: &'ast Generics) {