Prefer Default::default over FxHash*::default in struct constructors

Author: oli-obk

src/bootstrap/cache.rs

@@ -169,19 +169,13 @@ impl Ord for Interned<String> {
     }
 }
 
-struct TyIntern<T> {
+#[derive(Default)]
+struct TyIntern<T: Hash + Clone + Eq> {
     items: Vec<T>,
     set: HashMap<T, Interned<T>>,
 }
 
 impl<T: Hash + Clone + Eq> TyIntern<T> {
-    fn new() -> TyIntern<T> {
-        TyIntern {
-            items: Vec::new(),
-            set: HashMap::new(),
-        }
-    }
-
     fn intern_borrow<B>(&mut self, item: &B) -> Interned<T>
     where
         B: Eq + Hash + ToOwned<Owned=T> + ?Sized,
@@ -212,19 +206,13 @@ impl<T: Hash + Clone + Eq> TyIntern<T> {
     }
 }
 
+#[derive(Default)]
 pub struct Interner {
     strs: Mutex<TyIntern<String>>,
     paths: Mutex<TyIntern<PathBuf>>,
 }
 
 impl Interner {
-    fn new() -> Interner {
-        Interner {
-            strs: Mutex::new(TyIntern::new()),
-            paths: Mutex::new(TyIntern::new()),
-        }
-    }
-
     pub fn intern_str(&self, s: &str) -> Interned<String> {
         self.strs.lock().unwrap().intern_borrow(s)
     }
@@ -238,7 +226,7 @@ impl Interner {
 }
 
 lazy_static! {
-    pub static ref INTERNER: Interner = Interner::new();
+    pub static ref INTERNER: Interner = Interner::default();
 }
 
 /// This is essentially a HashMap which allows storing any type in its input and

src/libarena/lib.rs

@@ -114,10 +114,9 @@ impl<T> TypedArenaChunk<T> {
 
 const PAGE: usize = 4096;
 
-impl<T> TypedArena<T> {
+impl<T> Default for TypedArena<T> {
     /// Creates a new `TypedArena`.
-    #[inline]
-    pub fn new() -> TypedArena<T> {
+    fn default() -> TypedArena<T> {
         TypedArena {
             // We set both `ptr` and `end` to 0 so that the first call to
             // alloc() will trigger a grow().
@@ -127,7 +126,9 @@ impl<T> TypedArena<T> {
             _own: PhantomData,
         }
     }
+}
 
+impl<T> TypedArena<T> {
     /// Allocates an object in the `TypedArena`, returning a reference to it.
     #[inline]
     pub fn alloc(&self, object: T) -> &mut T {
@@ -296,15 +297,17 @@ pub struct DroplessArena {
 
 unsafe impl Send for DroplessArena {}
 
-impl DroplessArena {
-    pub fn new() -> DroplessArena {
+impl Default for DroplessArena {
+    fn default() -> DroplessArena {
         DroplessArena {
             ptr: Cell::new(0 as *mut u8),
             end: Cell::new(0 as *mut u8),
-            chunks: RefCell::new(vec![]),
+            chunks: Default::default(),
         }
     }
+}
 
+impl DroplessArena {
     pub fn in_arena<T: ?Sized>(&self, ptr: *const T) -> bool {
         let ptr = ptr as *const u8 as *mut u8;
         for chunk in &*self.chunks.borrow() {
@@ -419,18 +422,13 @@ impl DroplessArena {
     }
 }
 
+#[derive(Default)]
+// FIXME(@Zoxc): this type is entirely unused in rustc
 pub struct SyncTypedArena<T> {
     lock: MTLock<TypedArena<T>>,
 }
 
 impl<T> SyncTypedArena<T> {
-    #[inline(always)]
-    pub fn new() -> SyncTypedArena<T> {
-        SyncTypedArena {
-            lock: MTLock::new(TypedArena::new())
-        }
-    }
-
     #[inline(always)]
     pub fn alloc(&self, object: T) -> &mut T {
         // Extend the lifetime of the result since it's limited to the lock guard
@@ -452,18 +450,12 @@ impl<T> SyncTypedArena<T> {
     }
 }
 
+#[derive(Default)]
 pub struct SyncDroplessArena {
     lock: MTLock<DroplessArena>,
 }
 
 impl SyncDroplessArena {
-    #[inline(always)]
-    pub fn new() -> SyncDroplessArena {
-        SyncDroplessArena {
-            lock: MTLock::new(DroplessArena::new())
-        }
-    }
-
     #[inline(always)]
     pub fn in_arena<T: ?Sized>(&self, ptr: *const T) -> bool {
         self.lock.lock().in_arena(ptr)

src/librustc/dep_graph/cgu_reuse_tracker.rs

@@ -51,8 +51,8 @@ pub struct CguReuseTracker {
 impl CguReuseTracker {
     pub fn new() -> CguReuseTracker {
         let data = TrackerData {
-            actual_reuse: FxHashMap::default(),
-            expected_reuse: FxHashMap::default(),
+            actual_reuse: Default::default(),
+            expected_reuse: Default::default(),
         };
 
         CguReuseTracker {

src/librustc/dep_graph/dep_tracking_map.rs

@@ -36,7 +36,7 @@ impl<M: DepTrackingMapConfig> DepTrackingMap<M> {
         DepTrackingMap {
             phantom: PhantomData,
             graph,
-            map: FxHashMap::default(),
+            map: Default::default(),
         }
     }
 }

src/librustc/dep_graph/graph.rs

@@ -101,11 +101,11 @@ impl DepGraph {
         DepGraph {
             data: Some(Lrc::new(DepGraphData {
                 previous_work_products: prev_work_products,
-                dep_node_debug: Lock::new(FxHashMap::default()),
+                dep_node_debug: Lock::new(Default::default()),
                 current: Lock::new(CurrentDepGraph::new()),
                 previous: prev_graph,
                 colors: Lock::new(DepNodeColorMap::new(prev_graph_node_count)),
-                loaded_from_cache: Lock::new(FxHashMap::default()),
+                loaded_from_cache: Lock::new(Default::default()),
             })),
             fingerprints: Lrc::new(Lock::new(fingerprints)),
         }
@@ -209,7 +209,7 @@ impl DepGraph {
             |key| OpenTask::Regular(Lock::new(RegularOpenTask {
                 node: key,
                 reads: SmallVec::new(),
-                read_set: FxHashSet::default(),
+                read_set: Default::default(),
             })),
             |data, key, task| data.borrow_mut().complete_task(key, task))
     }
@@ -353,7 +353,7 @@ impl DepGraph {
             let (result, open_task) = ty::tls::with_context(|icx| {
                 let task = OpenTask::Anon(Lock::new(AnonOpenTask {
                     reads: SmallVec::new(),
-                    read_set: FxHashSet::default(),
+                    read_set: Default::default(),
                 }));
 
                 let r = {
@@ -937,7 +937,7 @@ impl CurrentDepGraph {
         CurrentDepGraph {
             nodes: IndexVec::new(),
             edges: IndexVec::new(),
-            node_to_node_index: FxHashMap::default(),
+            node_to_node_index: Default::default(),
             anon_id_seed: stable_hasher.finish(),
             forbidden_edge,
             total_read_count: 0,

src/librustc/dep_graph/prev.rs

@@ -13,7 +13,7 @@ use rustc_data_structures::fx::FxHashMap;
 use super::dep_node::DepNode;
 use super::serialized::{SerializedDepGraph, SerializedDepNodeIndex};
 
-#[derive(Debug, RustcEncodable, RustcDecodable)]
+#[derive(Debug, RustcEncodable, RustcDecodable, Default)]
 pub struct PreviousDepGraph {
     data: SerializedDepGraph,
     index: FxHashMap<DepNode, SerializedDepNodeIndex>,

src/librustc/dep_graph/serialized.rs

@@ -19,7 +19,7 @@ newtype_index! {
 }
 
 /// Data for use when recompiling the **current crate**.
-#[derive(Debug, RustcEncodable, RustcDecodable)]
+#[derive(Debug, RustcEncodable, RustcDecodable, Default)]
 pub struct SerializedDepGraph {
     /// The set of all DepNodes in the graph
     pub nodes: IndexVec<SerializedDepNodeIndex, DepNode>,
@@ -36,16 +36,6 @@ pub struct SerializedDepGraph {
 }
 
 impl SerializedDepGraph {
-
-    pub fn new() -> SerializedDepGraph {
-        SerializedDepGraph {
-            nodes: IndexVec::new(),
-            fingerprints: IndexVec::new(),
-            edge_list_indices: IndexVec::new(),
-            edge_list_data: Vec::new(),
-        }
-    }
-
     #[inline]
     pub fn edge_targets_from(&self,
                              source: SerializedDepNodeIndex)

src/librustc/hir/map/definitions.rs

@@ -421,10 +421,10 @@ impl Definitions {
             node_to_def_index: NodeMap(),
             def_index_to_node: [vec![], vec![]],
             node_to_hir_id: IndexVec::new(),
-            parent_modules_of_macro_defs: FxHashMap::default(),
-            expansions_that_defined: FxHashMap::default(),
-            next_disambiguator: FxHashMap::default(),
-            def_index_to_span: FxHashMap::default(),
+            parent_modules_of_macro_defs: Default::default(),
+            expansions_that_defined: Default::default(),
+            next_disambiguator: Default::default(),
+            def_index_to_span: Default::default(),
         }
     }
 

src/librustc/hir/map/hir_id_validator.rs

@@ -51,7 +51,7 @@ impl<'a, 'hir: 'a> OuterVisitor<'a, 'hir> {
         HirIdValidator {
             hir_map,
             owner_def_index: None,
-            hir_ids_seen: FxHashMap::default(),
+            hir_ids_seen: Default::default(),
             errors: Vec::new(),
         }
     }

src/librustc/ich/hcx.rs

@@ -370,7 +370,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for Span {
             // recursing every time.
             thread_local! {
                 static CACHE: RefCell<FxHashMap<hygiene::Mark, u64>> =
-                    RefCell::new(FxHashMap::default());
+                    RefCell::new(Default::default());
             }
 
             let sub_hash: u64 = CACHE.with(|cache| {