Convert more usages over

Author: czipperz

src/liballoc/collections/btree/map.rs

@@ -770,8 +770,8 @@ impl<K: Ord, V> BTreeMap<K, V> {
         }
 
         // First, we merge `self` and `other` into a sorted sequence in linear time.
-        let self_iter = mem::replace(self, BTreeMap::new()).into_iter();
-        let other_iter = mem::replace(other, BTreeMap::new()).into_iter();
+        let self_iter = mem::take(self).into_iter();
+        let other_iter = mem::take(other).into_iter();
         let iter = MergeIter {
             left: self_iter.peekable(),
             right: other_iter.peekable(),

src/liballoc/collections/linked_list.rs

@@ -708,7 +708,7 @@ impl<T> LinkedList<T> {
         let len = self.len();
         assert!(at <= len, "Cannot split off at a nonexistent index");
         if at == 0 {
-            return mem::replace(self, Self::new());
+            return mem::take(self);
         } else if at == len {
             return Self::new();
         }

src/liballoc/str.rs

@@ -203,7 +203,7 @@ impl ToOwned for str {
     }
 
     fn clone_into(&self, target: &mut String) {
-        let mut b = mem::replace(target, String::new()).into_bytes();
+        let mut b = mem::take(target).into_bytes();
         self.as_bytes().clone_into(&mut b);
         *target = unsafe { String::from_utf8_unchecked(b) }
     }

src/librustc/hir/lowering.rs

@@ -1278,8 +1278,8 @@ impl<'a> LoweringContext<'a> {
         let was_in_loop_condition = self.is_in_loop_condition;
         self.is_in_loop_condition = false;
 
-        let catch_scopes = mem::replace(&mut self.catch_scopes, Vec::new());
-        let loop_scopes = mem::replace(&mut self.loop_scopes, Vec::new());
+        let catch_scopes = mem::take(&mut self.catch_scopes);
+        let loop_scopes = mem::take(&mut self.loop_scopes);
         let ret = f(self);
         self.catch_scopes = catch_scopes;
         self.loop_scopes = loop_scopes;

src/librustc/infer/nll_relate/mod.rs

@@ -364,7 +364,7 @@ where
         // been fully instantiated and hence the set of scopes we have
         // doesn't matter -- just to be sure, put an empty vector
         // in there.
-        let old_a_scopes = ::std::mem::replace(pair.vid_scopes(self), vec![]);
+        let old_a_scopes = ::std::mem::take(pair.vid_scopes(self));
 
         // Relate the generalized kind to the original one.
         let result = pair.relate_generalized_ty(self, generalized_ty);

src/librustc/infer/outlives/obligations.rs

@@ -112,7 +112,7 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
 
     /// Trait queries just want to pass back type obligations "as is"
     pub fn take_registered_region_obligations(&self) -> Vec<(hir::HirId, RegionObligation<'tcx>)> {
-        ::std::mem::replace(&mut *self.region_obligations.borrow_mut(), vec![])
+        ::std::mem::take(&mut *self.region_obligations.borrow_mut())
     }
 
     /// Process the region obligations that must be proven (during

src/librustc/infer/region_constraints/mod.rs

@@ -410,7 +410,7 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
             *any_unifications = false;
         }
 
-        mem::replace(data, RegionConstraintData::default())
+        mem::take(data)
     }
 
     pub fn data(&self) -> &RegionConstraintData<'tcx> {

src/librustc/middle/region.rs

@@ -1375,7 +1375,7 @@ impl<'tcx> Visitor<'tcx> for RegionResolutionVisitor<'tcx> {
 
         let outer_ec = mem::replace(&mut self.expr_and_pat_count, 0);
         let outer_cx = self.cx;
-        let outer_ts = mem::replace(&mut self.terminating_scopes, FxHashSet::default());
+        let outer_ts = mem::take(&mut self.terminating_scopes);
         self.terminating_scopes.insert(body.value.hir_id.local_id);
 
         if let Some(root_id) = self.cx.root_id {

src/librustc/middle/resolve_lifetime.rs

@@ -18,7 +18,7 @@ use errors::{Applicability, DiagnosticBuilder};
 use rustc_macros::HashStable;
 use std::borrow::Cow;
 use std::cell::Cell;
-use std::mem::replace;
+use std::mem::{replace, take};
 use syntax::ast;
 use syntax::attr;
 use syntax::ptr::P;
@@ -441,7 +441,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
 
     fn visit_nested_body(&mut self, body: hir::BodyId) {
         // Each body has their own set of labels, save labels.
-        let saved = replace(&mut self.labels_in_fn, vec![]);
+        let saved = take(&mut self.labels_in_fn);
         let body = self.tcx.hir().body(body);
         extract_labels(self, body);
         self.with(
@@ -1405,9 +1405,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             lifetime_uses,
             ..
         } = self;
-        let labels_in_fn = replace(&mut self.labels_in_fn, vec![]);
-        let xcrate_object_lifetime_defaults =
-            replace(&mut self.xcrate_object_lifetime_defaults, DefIdMap::default());
+        let labels_in_fn = take(&mut self.labels_in_fn);
+        let xcrate_object_lifetime_defaults = take(&mut self.xcrate_object_lifetime_defaults);
         let mut this = LifetimeContext {
             tcx: *tcx,
             map: map,

src/librustc_codegen_llvm/back/archive.rs

@@ -205,8 +205,8 @@ impl<'a> LlvmArchiveBuilder<'a> {
     }
 
     fn build_with_llvm(&mut self, kind: ArchiveKind) -> io::Result<()> {
-        let removals = mem::replace(&mut self.removals, Vec::new());
-        let mut additions = mem::replace(&mut self.additions, Vec::new());
+        let removals = mem::take(&mut self.removals);
+        let mut additions = mem::take(&mut self.additions);
         let mut strings = Vec::new();
         let mut members = Vec::new();