From 883d0a7aa541abc900e2b597e847bd3140263df4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20Ber=C3=A1nek?= <berykubik@gmail.com>
Date: Wed, 8 Dec 2021 22:56:26 +0100
Subject: [PATCH] Use Vec extend instead of repeated pushes in several places

---
 compiler/rustc_mir_transform/src/coverage/spans.rs           | 4 +---
 compiler/rustc_trait_selection/src/traits/coherence.rs       | 4 +---
 .../src/traits/select/candidate_assembly.rs                  | 4 +---
 compiler/rustc_typeck/src/check/mod.rs                       | 5 ++---
 compiler/rustc_typeck/src/check/upvar.rs                     | 5 +----
 5 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs
index 146cabf350880..01e72a6c1588d 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans.rs
@@ -329,9 +329,7 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
     fn mir_to_initial_sorted_coverage_spans(&self) -> Vec<CoverageSpan> {
         let mut initial_spans = Vec::<CoverageSpan>::with_capacity(self.mir_body.num_nodes() * 2);
         for (bcb, bcb_data) in self.basic_coverage_blocks.iter_enumerated() {
-            for coverage_span in self.bcb_to_initial_coverage_spans(bcb, bcb_data) {
-                initial_spans.push(coverage_span);
-            }
+            initial_spans.extend(self.bcb_to_initial_coverage_spans(bcb, bcb_data));
         }
 
         if initial_spans.is_empty() {
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 42d3194aed48a..aec9da9f8d4f8 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -498,9 +498,7 @@ fn orphan_check_trait_ref<'tcx>(
             return Err(OrphanCheckErr::UncoveredTy(input_ty, local_type));
         }
 
-        for input_ty in non_local_tys {
-            non_local_spans.push((input_ty, i == 0));
-        }
+        non_local_spans.extend(non_local_tys.into_iter().map(|input_ty| (input_ty, i == 0)));
     }
     // If we exit above loop, never found a local type.
     debug!("orphan_check_trait_ref: no local type");
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 6e3e3b9b14480..4d9559c96af0e 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -362,9 +362,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .infcx
             .probe(|_| self.match_projection_obligation_against_definition_bounds(obligation));
 
-        for predicate_index in result {
-            candidates.vec.push(ProjectionCandidate(predicate_index));
-        }
+        candidates.vec.extend(result.into_iter().map(ProjectionCandidate));
     }
 
     /// Given an obligation like `<SomeTrait for T>`, searches the obligations that the caller
diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs
index 7bfd3f0ee8047..2e80f85972fa7 100644
--- a/compiler/rustc_typeck/src/check/mod.rs
+++ b/compiler/rustc_typeck/src/check/mod.rs
@@ -686,9 +686,8 @@ fn bounds_from_generic_predicates<'tcx>(
     };
     let mut where_clauses = vec![];
     for (ty, bounds) in types {
-        for bound in &bounds {
-            where_clauses.push(format!("{}: {}", ty, tcx.def_path_str(*bound)));
-        }
+        where_clauses
+            .extend(bounds.into_iter().map(|bound| format!("{}: {}", ty, tcx.def_path_str(bound))));
     }
     for projection in &projections {
         let p = projection.skip_binder();
diff --git a/compiler/rustc_typeck/src/check/upvar.rs b/compiler/rustc_typeck/src/check/upvar.rs
index 41bbf322a6ecc..a98afd1e3e1dc 100644
--- a/compiler/rustc_typeck/src/check/upvar.rs
+++ b/compiler/rustc_typeck/src/check/upvar.rs
@@ -904,10 +904,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> MigrationWarningReason {
         let mut reasons = MigrationWarningReason::default();
 
-        for auto_trait in auto_trait_reasons {
-            reasons.auto_traits.push(auto_trait);
-        }
-
+        reasons.auto_traits.extend(auto_trait_reasons);
         reasons.drop_order = drop_order;
 
         reasons