Auto merge of #22930 - Gankro:entry_3, r=aturon

RFC pending, but this is the patch that does it.

Totally untested. Likely needs some removed imports. std::collections docs should also be updated to provide better examples.

Closes #23508

src/libcollections/btree/map.rs

@@ -1143,15 +1143,39 @@ fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
 }
 
 impl<'a, K: Ord, V> Entry<'a, K, V> {
-    /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
     #[unstable(feature = "std_misc",
                reason = "will soon be replaced by or_insert")]
+    #[deprecated(since = "1.0",
+                reason = "replaced with more ergonomic `or_insert` and `or_insert_with`")]
+    /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
     pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
         match self {
             Occupied(entry) => Ok(entry.into_mut()),
             Vacant(entry) => Err(entry),
         }
     }
+
+    #[unstable(feature = "collections",
+               reason = "matches entry v3 specification, waiting for dust to settle")]
+    /// Ensures a value is in the entry by inserting the default if empty, and returns
+    /// a mutable reference to the value in the entry.
+    pub fn or_insert(self, default: V) -> &'a mut V {
+        match self {
+            Occupied(entry) => entry.into_mut(),
+            Vacant(entry) => entry.insert(default),
+        }
+    }
+
+    #[unstable(feature = "collections",
+               reason = "matches entry v3 specification, waiting for dust to settle")]
+    /// Ensures a value is in the entry by inserting the result of the default function if empty,
+    /// and returns a mutable reference to the value in the entry.
+    pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
+        match self {
+            Occupied(entry) => entry.into_mut(),
+            Vacant(entry) => entry.insert(default()),
+        }
+    }
 }
 
 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
@@ -1563,21 +1587,12 @@ pub fn range_mut<'a>(&'a mut self, min: Bound<&K>, max: Bound<&K>) -> RangeMut<'
     /// ```
     /// # #![feature(collections)]
     /// use std::collections::BTreeMap;
-    /// use std::collections::btree_map::Entry;
     ///
     /// let mut count: BTreeMap<&str, usize> = BTreeMap::new();
     ///
     /// // count the number of occurrences of letters in the vec
-    /// for x in vec!["a","b","a","c","a","b"].iter() {
-    ///     match count.entry(*x) {
-    ///         Entry::Vacant(view) => {
-    ///             view.insert(1);
-    ///         },
-    ///         Entry::Occupied(mut view) => {
-    ///             let v = view.get_mut();
-    ///             *v += 1;
-    ///         },
-    ///     }
+    /// for x in vec!["a","b","a","c","a","b"] {
+    ///     *count.entry(x).or_insert(0) += 1;
     /// }
     ///
     /// assert_eq!(count["a"], 3);

src/libcollections/vec_map.rs

@@ -632,21 +632,12 @@ pub fn remove(&mut self, key: &usize) -> Option<V> {
     /// ```
     /// # #![feature(collections)]
     /// use std::collections::VecMap;
-    /// use std::collections::vec_map::Entry;
     ///
     /// let mut count: VecMap<u32> = VecMap::new();
     ///
     /// // count the number of occurrences of numbers in the vec
-    /// for x in vec![1, 2, 1, 2, 3, 4, 1, 2, 4].iter() {
-    ///     match count.entry(*x) {
-    ///         Entry::Vacant(view) => {
-    ///             view.insert(1);
-    ///         },
-    ///         Entry::Occupied(mut view) => {
-    ///             let v = view.get_mut();
-    ///             *v += 1;
-    ///         },
-    ///     }
+    /// for x in vec![1, 2, 1, 2, 3, 4, 1, 2, 4] {
+    ///     *count.entry(x).or_insert(0) += 1;
     /// }
     ///
     /// assert_eq!(count[1], 3);
@@ -675,6 +666,8 @@ pub fn entry(&mut self, key: usize) -> Entry<V> {
 impl<'a, V> Entry<'a, V> {
     #[unstable(feature = "collections",
                reason = "will soon be replaced by or_insert")]
+    #[deprecated(since = "1.0",
+                reason = "replaced with more ergonomic `or_insert` and `or_insert_with`")]
     /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
     pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, V>> {
         match self {
@@ -682,6 +675,28 @@ pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, V>> {
             Vacant(entry) => Err(entry),
         }
     }
+
+    #[unstable(feature = "collections",
+               reason = "matches entry v3 specification, waiting for dust to settle")]
+    /// Ensures a value is in the entry by inserting the default if empty, and returns
+    /// a mutable reference to the value in the entry.
+    pub fn or_insert(self, default: V) -> &'a mut V {
+        match self {
+            Occupied(entry) => entry.into_mut(),
+            Vacant(entry) => entry.insert(default),
+        }
+    }
+
+    #[unstable(feature = "collections",
+               reason = "matches entry v3 specification, waiting for dust to settle")]
+    /// Ensures a value is in the entry by inserting the result of the default function if empty,
+    /// and returns a mutable reference to the value in the entry.
+    pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
+        match self {
+            Occupied(entry) => entry.into_mut(),
+            Vacant(entry) => entry.insert(default()),
+        }
+    }
 }
 
 impl<'a, V> VacantEntry<'a, V> {

src/librustc/metadata/loader.rs

@@ -426,8 +426,8 @@ fn find_library_crate(&mut self) -> Option<Library> {
             info!("lib candidate: {}", path.display());
 
             let hash_str = hash.to_string();
-            let slot = candidates.entry(hash_str).get().unwrap_or_else(
-                |vacant_entry| vacant_entry.insert((HashMap::new(), HashMap::new())));
+            let slot = candidates.entry(hash_str)
+                                 .or_insert_with(|| (HashMap::new(), HashMap::new()));
             let (ref mut rlibs, ref mut dylibs) = *slot;
             if rlib {
                 rlibs.insert(fs::realpath(path).unwrap(), kind);

src/librustc/middle/dataflow.rs

@@ -160,12 +160,7 @@ fn build_nodeid_to_index(decl: Option<&ast::FnDecl>,
 
     cfg.graph.each_node(|node_idx, node| {
         if let cfg::CFGNodeData::AST(id) = node.data {
-            match index.entry(id).get() {
-                Ok(v) => v.push(node_idx),
-                Err(e) => {
-                    e.insert(vec![node_idx]);
-                }
-            }
+            index.entry(id).or_insert(vec![]).push(node_idx);
         }
         true
     });
@@ -185,12 +180,7 @@ struct Formals<'a> {
         visit::walk_fn_decl(&mut formals, decl);
         impl<'a, 'v> visit::Visitor<'v> for Formals<'a> {
             fn visit_pat(&mut self, p: &ast::Pat) {
-                match self.index.entry(p.id).get() {
-                    Ok(v) => v.push(self.entry),
-                    Err(e) => {
-                        e.insert(vec![self.entry]);
-                    }
-                }
+                self.index.entry(p.id).or_insert(vec![]).push(self.entry);
                 visit::walk_pat(self, p)
             }
         }

src/librustc/middle/traits/fulfill.rs

@@ -11,7 +11,6 @@
 use middle::infer::{InferCtxt};
 use middle::ty::{self, RegionEscape, Ty};
 use std::collections::HashSet;
-use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::default::Default;
 use syntax::ast;
 use util::common::ErrorReported;
@@ -437,9 +436,7 @@ fn register_region_obligation<'tcx>(tcx: &ty::ctxt<'tcx>,
     debug!("register_region_obligation({})",
            region_obligation.repr(tcx));
 
-    match region_obligations.entry(region_obligation.cause.body_id) {
-        Vacant(entry) => { entry.insert(vec![region_obligation]); },
-        Occupied(mut entry) => { entry.get_mut().push(region_obligation); },
-    }
+    region_obligations.entry(region_obligation.cause.body_id).or_insert(vec![])
+        .push(region_obligation);
 
 }

src/librustc/middle/ty.rs

@@ -5669,9 +5669,7 @@ pub fn lookup_field_type<'tcx>(tcx: &ctxt<'tcx>,
         node_id_to_type(tcx, id.node)
     } else {
         let mut tcache = tcx.tcache.borrow_mut();
-        let pty = tcache.entry(id).get().unwrap_or_else(
-            |vacant_entry| vacant_entry.insert(csearch::get_field_type(tcx, struct_id, id)));
-        pty.ty
+        tcache.entry(id).or_insert_with(|| csearch::get_field_type(tcx, struct_id, id)).ty
     };
     ty.subst(tcx, substs)
 }
@@ -6819,9 +6817,7 @@ pub fn replace_late_bound_regions<'tcx, T, F>(
         debug!("region={}", region.repr(tcx));
         match region {
             ty::ReLateBound(debruijn, br) if debruijn.depth == current_depth => {
-                let region =
-                    * map.entry(br).get().unwrap_or_else(
-                        |vacant_entry| vacant_entry.insert(mapf(br)));
+                let region = *map.entry(br).or_insert_with(|| mapf(br));
 
                 if let ty::ReLateBound(debruijn1, br) = region {
                     // If the callback returns a late-bound region,

src/librustc/session/config.rs

@@ -35,7 +35,6 @@
 
 use getopts;
 use std::collections::HashMap;
-use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::env;
 use std::fmt;
 use std::path::PathBuf;
@@ -1037,10 +1036,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
             None => early_error("--extern value must be of the format `foo=bar`"),
         };
 
-        match externs.entry(name.to_string()) {
-            Vacant(entry) => { entry.insert(vec![location.to_string()]); },
-            Occupied(mut entry) => { entry.get_mut().push(location.to_string()); },
-        }
+        externs.entry(name.to_string()).or_insert(vec![]).push(location.to_string());
     }
 
     let crate_name = matches.opt_str("crate-name");

src/librustc_resolve/lib.rs

@@ -26,7 +26,6 @@
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
 #![feature(staged_api)]
-#![feature(std_misc)]
 
 #[macro_use] extern crate log;
 #[macro_use] extern crate syntax;

src/librustc_resolve/resolve_imports.rs

@@ -836,11 +836,8 @@ fn merge_import_resolution(&mut self,
         let is_public = import_directive.is_public;
 
         let mut import_resolutions = module_.import_resolutions.borrow_mut();
-        let dest_import_resolution = import_resolutions.entry(name).get().unwrap_or_else(
-            |vacant_entry| {
-                // Create a new import resolution from this child.
-                vacant_entry.insert(ImportResolution::new(id, is_public))
-            });
+        let dest_import_resolution = import_resolutions.entry(name)
+            .or_insert_with(|| ImportResolution::new(id, is_public));
 
         debug!("(resolving glob import) writing resolution `{}` in `{}` \
                to `{}`",

src/librustc_typeck/check/mod.rs

@@ -112,7 +112,6 @@
 use util::lev_distance::lev_distance;
 
 use std::cell::{Cell, Ref, RefCell};
-use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::mem::replace;
 use std::rc::Rc;
 use std::iter::repeat;
@@ -1362,11 +1361,7 @@ fn record_deferred_call_resolution(&self,
                                        closure_def_id: ast::DefId,
                                        r: DeferredCallResolutionHandler<'tcx>) {
         let mut deferred_call_resolutions = self.inh.deferred_call_resolutions.borrow_mut();
-        let mut vec = match deferred_call_resolutions.entry(closure_def_id) {
-            Occupied(entry) => entry.into_mut(),
-            Vacant(entry) => entry.insert(Vec::new()),
-        };
-        vec.push(r);
+        deferred_call_resolutions.entry(closure_def_id).or_insert(vec![]).push(r);
     }
 
     fn remove_deferred_call_resolutions(&self,

src/librustdoc/html/render.rs

@@ -876,9 +876,7 @@ fn fold_item(&mut self, item: clean::Item) -> Option<clean::Item> {
         if let clean::ImplItem(ref i) = item.inner {
             match i.trait_ {
                 Some(clean::ResolvedPath{ did, .. }) => {
-                    let v = self.implementors.entry(did).get().unwrap_or_else(
-                        |vacant_entry| vacant_entry.insert(Vec::with_capacity(1)));
-                    v.push(Implementor {
+                    self.implementors.entry(did).or_insert(vec![]).push(Implementor {
                         def_id: item.def_id,
                         generics: i.generics.clone(),
                         trait_: i.trait_.as_ref().unwrap().clone(),
@@ -1080,9 +1078,7 @@ fn fold_item(&mut self, item: clean::Item) -> Option<clean::Item> {
                         };
 
                         if let Some(did) = did {
-                            let v = self.impls.entry(did).get().unwrap_or_else(
-                                |vacant_entry| vacant_entry.insert(Vec::with_capacity(1)));
-                            v.push(Impl {
+                            self.impls.entry(did).or_insert(vec![]).push(Impl {
                                 impl_: i,
                                 dox: dox,
                                 stability: item.stability.clone(),
@@ -1334,9 +1330,8 @@ fn build_sidebar_items(&self, m: &clean::Module) -> HashMap<String, Vec<NameDoc>
                 Some(ref s) => s.to_string(),
             };
             let short = short.to_string();
-            let v = map.entry(short).get().unwrap_or_else(
-                |vacant_entry| vacant_entry.insert(Vec::with_capacity(1)));
-            v.push((myname, Some(plain_summary_line(item.doc_value()))));
+            map.entry(short).or_insert(vec![])
+                .push((myname, Some(plain_summary_line(item.doc_value()))));
         }
 
         for (_, items) in &mut map {

src/librustdoc/lib.rs

@@ -352,9 +352,7 @@ fn parse_externs(matches: &getopts::Matches) -> Result<core::Externs, String> {
             }
         };
         let name = name.to_string();
-        let locs = externs.entry(name).get().unwrap_or_else(
-            |vacant_entry| vacant_entry.insert(Vec::with_capacity(1)));
-        locs.push(location.to_string());
+        externs.entry(name).or_insert(vec![]).push(location.to_string());
     }
     Ok(externs)
 }

src/libstd/collections/hash/map.rs

@@ -23,7 +23,7 @@
 use iter::{self, Iterator, ExactSizeIterator, IntoIterator, IteratorExt, FromIterator, Extend, Map};
 use marker::Sized;
 use mem::{self, replace};
-use ops::{Deref, FnMut, Index};
+use ops::{Deref, FnMut, FnOnce, Index};
 use option::Option::{self, Some, None};
 use rand::{self, Rng};
 use result::Result::{self, Ok, Err};
@@ -1488,12 +1488,37 @@ impl<'a, K, V> Entry<'a, K, V> {
     /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant.
     #[unstable(feature = "std_misc",
                reason = "will soon be replaced by or_insert")]
+    #[deprecated(since = "1.0",
+                reason = "replaced with more ergonomic `or_insert` and `or_insert_with`")]
+    /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
     pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
         match self {
             Occupied(entry) => Ok(entry.into_mut()),
             Vacant(entry) => Err(entry),
         }
     }
+
+    #[unstable(feature = "collections",
+               reason = "matches entry v3 specification, waiting for dust to settle")]
+    /// Ensures a value is in the entry by inserting the default if empty, and returns
+    /// a mutable reference to the value in the entry.
+    pub fn or_insert(self, default: V) -> &'a mut V {
+        match self {
+            Occupied(entry) => entry.into_mut(),
+            Vacant(entry) => entry.insert(default),
+        }
+    }
+
+    #[unstable(feature = "collections",
+               reason = "matches entry v3 specification, waiting for dust to settle")]
+    /// Ensures a value is in the entry by inserting the result of the default function if empty,
+    /// and returns a mutable reference to the value in the entry.
+    pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
+        match self {
+            Occupied(entry) => entry.into_mut(),
+            Vacant(entry) => entry.insert(default()),
+        }
+    }
 }
 
 impl<'a, K, V> OccupiedEntry<'a, K, V> {

src/libstd/collections/mod.rs

@@ -307,10 +307,7 @@
 //! let message = "she sells sea shells by the sea shore";
 //!
 //! for c in message.chars() {
-//!     match count.entry(c) {
-//!         Entry::Vacant(entry) => { entry.insert(1); },
-//!         Entry::Occupied(mut entry) => *entry.get_mut() += 1,
-//!     }
+//!     *count.entry(c).or_insert(0) += 1;
 //! }
 //!
 //! assert_eq!(count.get(&'s'), Some(&8));
@@ -343,10 +340,7 @@
 //! for id in orders.into_iter() {
 //!     // If this is the first time we've seen this customer, initialize them
 //!     // with no blood alcohol. Otherwise, just retrieve them.
-//!     let person = match blood_alcohol.entry(id) {
-//!         Entry::Vacant(entry) => entry.insert(Person{id: id, blood_alcohol: 0.0}),
-//!         Entry::Occupied(entry) => entry.into_mut(),
-//!     };
+//!     let person = blood_alcohol.entry(id).or_insert(Person{id: id, blood_alcohol: 0.0});
 //!
 //!     // Reduce their blood alcohol level. It takes time to order and drink a beer!
 //!     person.blood_alcohol *= 0.9;

src/libsyntax/ext/mtwt.rs

@@ -66,9 +66,8 @@ pub fn apply_mark(m: Mrk, ctxt: SyntaxContext) -> SyntaxContext {
 /// Extend a syntax context with a given mark and sctable (explicit memoization)
 fn apply_mark_internal(m: Mrk, ctxt: SyntaxContext, table: &SCTable) -> SyntaxContext {
     let key = (ctxt, m);
-    * table.mark_memo.borrow_mut().entry(key).get().unwrap_or_else(
-          |vacant_entry|
-              vacant_entry.insert(idx_push(&mut *table.table.borrow_mut(), Mark(m, ctxt))))
+    * table.mark_memo.borrow_mut().entry(key)
+        .or_insert_with(|| idx_push(&mut *table.table.borrow_mut(), Mark(m, ctxt)))
 }
 
 /// Extend a syntax context with a given rename
@@ -84,9 +83,8 @@ fn apply_rename_internal(id: Ident,
                        table: &SCTable) -> SyntaxContext {
     let key = (ctxt, id, to);
 
-    * table.rename_memo.borrow_mut().entry(key).get().unwrap_or_else(
-          |vacant_entry|
-              vacant_entry.insert(idx_push(&mut *table.table.borrow_mut(), Rename(id, to, ctxt))))
+    * table.rename_memo.borrow_mut().entry(key)
+        .or_insert_with(|| idx_push(&mut *table.table.borrow_mut(), Rename(id, to, ctxt)))
 }
 
 /// Apply a list of renamings to a context

src/libsyntax/lib.rs

@@ -35,7 +35,6 @@
 #![feature(quote, unsafe_destructor)]
 #![feature(rustc_private)]
 #![feature(staged_api)]
-#![feature(std_misc)]
 #![feature(unicode)]
 #![feature(path_ext)]
 #![feature(str_char)]