Fixed all unnecessary muts in language core

src/liballoc/btree/node.rs

@@ -1037,7 +1037,7 @@ impl<'a, K: 'a, V: 'a, NodeType>
         Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
 
     pub fn into_kv_mut(self) -> (&'a mut K, &'a mut V) {
-        let (mut keys, mut vals) = self.node.into_slices_mut();
+        let (keys, vals) = self.node.into_slices_mut();
         unsafe {
             (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
         }
@@ -1047,7 +1047,7 @@ pub fn into_kv_mut(self) -> (&'a mut K, &'a mut V) {
 impl<'a, K, V, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
     pub fn kv_mut(&mut self) -> (&mut K, &mut V) {
         unsafe {
-            let (mut keys, mut vals) = self.node.reborrow_mut().into_slices_mut();
+            let (keys, vals) = self.node.reborrow_mut().into_slices_mut();
             (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
         }
     }

src/liballoc/vec.rs

@@ -1751,7 +1751,7 @@ impl<'a, T> IntoIterator for &'a mut Vec<T> {
     type Item = &'a mut T;
     type IntoIter = slice::IterMut<'a, T>;
 
-    fn into_iter(mut self) -> slice::IterMut<'a, T> {
+    fn into_iter(self) -> slice::IterMut<'a, T> {
         self.iter_mut()
     }
 }

src/liballoc/vec_deque.rs

@@ -2394,7 +2394,7 @@ impl<'a, T> IntoIterator for &'a mut VecDeque<T> {
     type Item = &'a mut T;
     type IntoIter = IterMut<'a, T>;
 
-    fn into_iter(mut self) -> IterMut<'a, T> {
+    fn into_iter(self) -> IterMut<'a, T> {
         self.iter_mut()
     }
 }

src/libcore/ops/function.rs

@@ -187,7 +187,7 @@ impl<'a,A,F:?Sized> FnOnce<A> for &'a mut F
         where F : FnMut<A>
     {
         type Output = F::Output;
-        extern "rust-call" fn call_once(mut self, args: A) -> F::Output {
+        extern "rust-call" fn call_once(self, args: A) -> F::Output {
             (*self).call_mut(args)
         }
     }

src/libcore/option.rs

@@ -872,7 +872,7 @@ impl<'a, T> IntoIterator for &'a mut Option<T> {
     type Item = &'a mut T;
     type IntoIter = IterMut<'a, T>;
 
-    fn into_iter(mut self) -> IterMut<'a, T> {
+    fn into_iter(self) -> IterMut<'a, T> {
         self.iter_mut()
     }
 }

src/libcore/result.rs

@@ -909,7 +909,7 @@ impl<'a, T, E> IntoIterator for &'a mut Result<T, E> {
     type Item = &'a mut T;
     type IntoIter = IterMut<'a, T>;
 
-    fn into_iter(mut self) -> IterMut<'a, T> {
+    fn into_iter(self) -> IterMut<'a, T> {
         self.iter_mut()
     }
 }

src/librustc/infer/error_reporting/mod.rs

@@ -415,8 +415,8 @@ fn note_error_origin(&self,
     /// -------- this type is the same as a type argument in the other type, not highlighted
     /// ```
     fn highlight_outer(&self,
-                       mut value: &mut DiagnosticStyledString,
-                       mut other_value: &mut DiagnosticStyledString,
+                       value: &mut DiagnosticStyledString,
+                       other_value: &mut DiagnosticStyledString,
                        name: String,
                        sub: &ty::subst::Substs<'tcx>,
                        pos: usize,

src/librustc/traits/mod.rs

@@ -560,7 +560,7 @@ pub fn fully_normalize<'a, 'gcx, 'tcx, T>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
 {
     debug!("fully_normalize(value={:?})", value);
 
-    let mut selcx = &mut SelectionContext::new(infcx);
+    let selcx = &mut SelectionContext::new(infcx);
     // FIXME (@jroesch) ISSUE 26721
     // I'm not sure if this is a bug or not, needs further investigation.
     // It appears that by reusing the fulfillment_cx here we incur more

src/librustc/traits/select.rs

@@ -494,7 +494,7 @@ pub fn select(&mut self, obligation: &TraitObligation<'tcx>)
             never_obligation.predicate = never_obligation.predicate.map_bound(|mut trait_pred| {
                 // Swap out () with ! so we can check if the trait is impld for !
                 {
-                    let mut trait_ref = &mut trait_pred.trait_ref;
+                    let trait_ref = &mut trait_pred.trait_ref;
                     let unit_substs = trait_ref.substs;
                     let mut never_substs = Vec::with_capacity(unit_substs.len());
                     never_substs.push(From::from(tcx.types.never));

src/librustc/ty/inhabitedness/mod.rs

@@ -171,7 +171,7 @@ fn uninhabited_from_inner(
         match self.sty {
             TyAdt(def, substs) => {
                 {
-                    let mut substs_set = visited.entry(def.did).or_insert(FxHashSet::default());
+                    let substs_set = visited.entry(def.did).or_insert(FxHashSet::default());
                     if !substs_set.insert(substs) {
                         // We are already calculating the inhabitedness of this type.
                         // The type must contain a reference to itself. Break the
@@ -193,7 +193,7 @@ fn uninhabited_from_inner(
                     }
                 }
                 let ret = def.uninhabited_from(visited, tcx, substs);
-                let mut substs_set = visited.get_mut(&def.did).unwrap();
+                let substs_set = visited.get_mut(&def.did).unwrap();
                 substs_set.remove(substs);
                 ret
             },

src/librustc_allocator/expand.rs

@@ -188,7 +188,7 @@ fn attrs(&self) -> Vec<Attribute> {
     fn arg_ty(&self,
               ty: &AllocatorTy,
               args: &mut Vec<Arg>,
-              mut ident: &mut FnMut() -> Ident) -> P<Expr> {
+              ident: &mut FnMut() -> Ident) -> P<Expr> {
         match *ty {
             AllocatorTy::Layout => {
                 let usize = self.cx.path_ident(self.span, Ident::from_str("usize"));
@@ -263,7 +263,7 @@ fn arg_ty(&self,
     fn ret_ty(&self,
               ty: &AllocatorTy,
               args: &mut Vec<Arg>,
-              mut ident: &mut FnMut() -> Ident,
+              ident: &mut FnMut() -> Ident,
               expr: P<Expr>) -> (P<Ty>, P<Expr>)
     {
         match *ty {

src/librustc_borrowck/borrowck/mod.rs

@@ -98,7 +98,7 @@ fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId) {
     let body_id = tcx.hir.body_owned_by(owner_id);
     let tables = tcx.typeck_tables_of(owner_def_id);
     let region_maps = tcx.region_maps(owner_def_id);
-    let mut bccx = &mut BorrowckCtxt { tcx, tables, region_maps, owner_def_id };
+    let bccx = &mut BorrowckCtxt { tcx, tables, region_maps, owner_def_id };
 
     let body = bccx.tcx.hir.body(body_id);
 

src/librustc_data_structures/array_vec.rs

@@ -260,7 +260,7 @@ fn drop(&mut self) {
                 let start = source_array_vec.len();
                 let tail = self.tail_start;
                 {
-                    let mut arr = &mut source_array_vec.values as &mut [ManuallyDrop<_>];
+                    let arr = &mut source_array_vec.values as &mut [ManuallyDrop<_>];
                     let src = arr.as_ptr().offset(tail as isize);
                     let dst = arr.as_mut_ptr().offset(start as isize);
                     ptr::copy(src, dst, self.tail_len);

src/librustc_data_structures/bitvec.rs

@@ -166,7 +166,7 @@ fn range(&self, row: usize) -> (usize, usize) {
     pub fn add(&mut self, source: usize, target: usize) -> bool {
         let (start, _) = self.range(source);
         let (word, mask) = word_mask(target);
-        let mut vector = &mut self.vector[..];
+        let vector = &mut self.vector[..];
         let v1 = vector[start + word];
         let v2 = v1 | mask;
         vector[start + word] = v2;

src/librustc_data_structures/indexed_vec.rs

@@ -259,7 +259,7 @@ impl<'a, I: Idx, T> IntoIterator for &'a mut IndexVec<I, T> {
     type IntoIter = slice::IterMut<'a, T>;
 
     #[inline]
-    fn into_iter(mut self) -> slice::IterMut<'a, T> {
+    fn into_iter(self) -> slice::IterMut<'a, T> {
         self.raw.iter_mut()
     }
 }

src/librustc_driver/lib.rs

@@ -422,7 +422,7 @@ fn show_content_with_pager(content: &String) {
 
     match Command::new(pager_name).stdin(Stdio::piped()).spawn() {
         Ok(mut pager) => {
-            if let Some(mut pipe) = pager.stdin.as_mut() {
+            if let Some(pipe) = pager.stdin.as_mut() {
                 if pipe.write_all(content.as_bytes()).is_err() {
                     fallback_to_println = true;
                 }

src/librustc_metadata/cstore_impl.rs

@@ -479,7 +479,7 @@ fn visible_parent_map<'a>(&'a self, sess: &Session) -> ::std::cell::Ref<'a, DefI
                 _ => {},
             }
 
-            let mut bfs_queue = &mut VecDeque::new();
+            let bfs_queue = &mut VecDeque::new();
             let mut add_child = |bfs_queue: &mut VecDeque<_>, child: def::Export, parent: DefId| {
                 let child = child.def.def_id();
 

src/librustc_mir/build/matches/mod.rs

@@ -206,7 +206,7 @@ pub fn schedule_drop_for_binding(&mut self, var: NodeId, span: Span) {
         self.schedule_drop(span, extent, &Lvalue::Local(local_id), var_ty);
     }
 
-    pub fn visit_bindings<F>(&mut self, pattern: &Pattern<'tcx>, mut f: &mut F)
+    pub fn visit_bindings<F>(&mut self, pattern: &Pattern<'tcx>, f: &mut F)
         where F: FnMut(&mut Self, Mutability, Name, NodeId, Span, Ty<'tcx>)
     {
         match *pattern.kind {

src/librustc_mir/transform/type_check.rs

@@ -720,7 +720,7 @@ fn normalize<T>(&mut self, value: &T) -> T
                value,
                obligations);
 
-        let mut fulfill_cx = &mut self.fulfillment_cx;
+        let fulfill_cx = &mut self.fulfillment_cx;
         for obligation in obligations {
             fulfill_cx.register_predicate_obligation(self.infcx, obligation);
         }

src/librustc_privacy/lib.rs

@@ -781,7 +781,7 @@ fn visit_item(&mut self, item: &'tcx hir::Item) {
             hir::ItemTrait(.., ref trait_item_refs) => {
                 self.check_item(item.id).generics().predicates();
                 for trait_item_ref in trait_item_refs {
-                    let mut check = self.check_item(trait_item_ref.id.node_id);
+                    let check = self.check_item(trait_item_ref.id.node_id);
                     check.generics().predicates();
                     if trait_item_ref.kind != hir::AssociatedItemKind::Type ||
                        trait_item_ref.defaultness.has_value() {
@@ -814,7 +814,7 @@ fn visit_item(&mut self, item: &'tcx hir::Item) {
             }
             hir::ItemImpl(.., ref trait_ref, _, ref impl_item_refs) => {
                 {
-                    let mut check = self.check_item(item.id);
+                    let check = self.check_item(item.id);
                     check.ty().generics().predicates();
                     if trait_ref.is_some() {
                         check.impl_trait_ref();

src/librustc_resolve/resolve_imports.rs

@@ -379,7 +379,7 @@ fn update_resolution<T, F>(&mut self, module: Module<'a>, ident: Ident, ns: Name
         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
         // during which the resolution might end up getting re-defined via a glob cycle.
         let (binding, t) = {
-            let mut resolution = &mut *self.resolution(module, ident, ns).borrow_mut();
+            let resolution = &mut *self.resolution(module, ident, ns).borrow_mut();
             let old_binding = resolution.binding();
 
             let t = f(self, resolution);

src/librustc_trans/base.rs

@@ -1465,7 +1465,7 @@ fn collect_and_partition_translation_items<'a, 'tcx>(scx: &SharedCrateContext<'a
                 let mut output = i.to_string(scx.tcx());
                 output.push_str(" @@");
                 let mut empty = Vec::new();
-                let mut cgus = item_to_cgus.get_mut(i).unwrap_or(&mut empty);
+                let cgus = item_to_cgus.get_mut(i).unwrap_or(&mut empty);
                 cgus.as_mut_slice().sort_by_key(|&(ref name, _)| name.clone());
                 cgus.dedup();
                 for &(ref cgu_name, (linkage, _)) in cgus.iter() {

src/librustc_trans/partitioning.rs

@@ -348,7 +348,7 @@ fn place_root_translation_items<'a, 'tcx, I>(scx: &SharedCrateContext<'a, 'tcx>,
                 CodegenUnit::empty(codegen_unit_name.clone())
             };
 
-            let mut codegen_unit = codegen_units.entry(codegen_unit_name.clone())
+            let codegen_unit = codegen_units.entry(codegen_unit_name.clone())
                                                 .or_insert_with(make_codegen_unit);
 
             let (linkage, visibility) = match trans_item.explicit_linkage(tcx) {

src/librustc_typeck/check/coercion.rs

@@ -1204,7 +1204,7 @@ fn coerce_inner<'a>(&mut self,
                     }
                 }
 
-                if let Some(mut augment_error) = augment_error {
+                if let Some(augment_error) = augment_error {
                     augment_error(&mut db);
                 }
 

src/librustc_typeck/check/method/probe.rs

@@ -538,7 +538,7 @@ fn assemble_inherent_impl_probe(&mut self, impl_def_id: DefId) {
             // We can't use normalize_associated_types_in as it will pollute the
             // fcx's fulfillment context after this probe is over.
             let cause = traits::ObligationCause::misc(self.span, self.body_id);
-            let mut selcx = &mut traits::SelectionContext::new(self.fcx);
+            let selcx = &mut traits::SelectionContext::new(self.fcx);
             let traits::Normalized { value: xform_self_ty, obligations } =
                 traits::normalize(selcx, self.param_env, cause, &xform_self_ty);
             debug!("assemble_inherent_impl_probe: xform_self_ty = {:?}",
@@ -749,7 +749,7 @@ fn assemble_extension_candidates_for_trait_impls(&mut self,
             // as it will pollute the fcx's fulfillment context after this probe
             // is over.
             let cause = traits::ObligationCause::misc(self.span, self.body_id);
-            let mut selcx = &mut traits::SelectionContext::new(self.fcx);
+            let selcx = &mut traits::SelectionContext::new(self.fcx);
             let traits::Normalized { value: xform_self_ty, obligations } =
                 traits::normalize(selcx, self.param_env, cause, &xform_self_ty);
 

src/librustc_typeck/check/mod.rs

@@ -4147,8 +4147,8 @@ fn check_block_with_expected(&self,
             let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
 
             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
-            let mut ctxt = enclosing_breakables.find_breakable(blk.id);
-            let mut coerce = ctxt.coerce.as_mut().unwrap();
+            let ctxt = enclosing_breakables.find_breakable(blk.id);
+            let coerce = ctxt.coerce.as_mut().unwrap();
             if let Some(tail_expr_ty) = tail_expr_ty {
                 let tail_expr = tail_expr.unwrap();
                 let cause = self.cause(tail_expr.span,

src/librustc_typeck/check/op.rs

@@ -300,7 +300,7 @@ fn check_str_addition(&self,
                           lhs_expr: &'gcx hir::Expr,
                           lhs_ty: Ty<'tcx>,
                           rhs_ty: Ty<'tcx>,
-                          mut err: &mut errors::DiagnosticBuilder) -> bool {
+                          err: &mut errors::DiagnosticBuilder) -> bool {
         // If this function returns true it means a note was printed, so we don't need
         // to print the normal "implementation of `std::ops::Add` might be missing" note
         let mut is_string_addition = false;

src/libstd/collections/hash/map.rs

@@ -1618,7 +1618,7 @@ impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S>
     type Item = (&'a K, &'a mut V);
     type IntoIter = IterMut<'a, K, V>;
 
-    fn into_iter(mut self) -> IterMut<'a, K, V> {
+    fn into_iter(self) -> IterMut<'a, K, V> {
         self.iter_mut()
     }
 }

src/libstd/sync/once.rs

@@ -267,7 +267,7 @@ pub fn call_once_force<F>(&'static self, f: F) where F: FnOnce(&OnceState) {
     #[cold]
     fn call_inner(&'static self,
                   ignore_poisoning: bool,
-                  mut init: &mut FnMut(bool)) {
+                  init: &mut FnMut(bool)) {
         let mut state = self.state.load(Ordering::SeqCst);
 
         'outer: loop {

src/libstd/sys/unix/rand.rs

@@ -12,13 +12,13 @@
 
 use mem;
 
-fn next_u32(mut fill_buf: &mut FnMut(&mut [u8])) -> u32 {
+fn next_u32(fill_buf: &mut FnMut(&mut [u8])) -> u32 {
     let mut buf: [u8; 4] = [0; 4];
     fill_buf(&mut buf);
     unsafe { mem::transmute::<[u8; 4], u32>(buf) }
 }
 
-fn next_u64(mut fill_buf: &mut FnMut(&mut [u8])) -> u64 {
+fn next_u64(fill_buf: &mut FnMut(&mut [u8])) -> u64 {
     let mut buf: [u8; 8] = [0; 8];
     fill_buf(&mut buf);
     unsafe { mem::transmute::<[u8; 8], u64>(buf) }

src/libsyntax/ext/tt/macro_parser.rs

@@ -211,7 +211,7 @@ pub enum NamedMatch {
 
 fn nameize<I: Iterator<Item=NamedMatch>>(sess: &ParseSess, ms: &[TokenTree], mut res: I)
                                              -> NamedParseResult {
-    fn n_rec<I: Iterator<Item=NamedMatch>>(sess: &ParseSess, m: &TokenTree, mut res: &mut I,
+    fn n_rec<I: Iterator<Item=NamedMatch>>(sess: &ParseSess, m: &TokenTree, res: &mut I,
              ret_val: &mut HashMap<Ident, Rc<NamedMatch>>)
              -> Result<(), (syntax_pos::Span, String)> {
         match *m {
@@ -445,7 +445,7 @@ pub fn parse(sess: &ParseSess,
         /* error messages here could be improved with links to orig. rules */
         if token_name_eq(&parser.token, &token::Eof) {
             if eof_items.len() == 1 {
-                let matches = eof_items[0].matches.iter_mut().map(|mut dv| {
+                let matches = eof_items[0].matches.iter_mut().map(|dv| {
                     Rc::make_mut(dv).pop().unwrap()
                 });
                 return nameize(sess, ms, matches);

src/libsyntax/ext/tt/macro_rules.rs

@@ -86,7 +86,7 @@ fn expand<'cx>(&self,
 
 fn trace_macros_note(cx: &mut ExtCtxt, sp: Span, message: String) {
     let sp = sp.macro_backtrace().last().map(|trace| trace.call_site).unwrap_or(sp);
-    let mut values: &mut Vec<String> = cx.expansions.entry(sp).or_insert_with(Vec::new);
+    let values: &mut Vec<String> = cx.expansions.entry(sp).or_insert_with(Vec::new);
     values.push(message);
 }