Use default_field_values more in Resolver

compiler/rustc_data_structures/src/fx.rs

@@ -28,3 +28,18 @@ macro_rules! define_stable_id_collections {
         pub type $entry_name<'a, T> = $crate::fx::IndexEntry<'a, $key, T>;
     };
 }
+
+pub mod default {
+    use super::{FxBuildHasher, FxHashMap, FxHashSet};
+
+    // FIXME: These two functions will become unnecessary after
+    // <https://github.com/rust-lang/rustc-hash/pull/63> lands and we start using the corresponding
+    // `rustc-hash` version. After that we can use `Default::default()` instead.
+    pub const fn fx_hash_map<K, V>() -> FxHashMap<K, V> {
+        FxHashMap::with_hasher(FxBuildHasher)
+    }
+
+    pub const fn fx_hash_set<V>() -> FxHashSet<V> {
+        FxHashSet::with_hasher(FxBuildHasher)
+    }
+}

compiler/rustc_data_structures/src/lib.rs

@@ -18,6 +18,8 @@
 #![feature(assert_matches)]
 #![feature(auto_traits)]
 #![feature(cfg_select)]
+#![feature(const_default)]
+#![feature(const_trait_impl)]
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]
 #![feature(extend_one)]

compiler/rustc_data_structures/src/unord.rs

@@ -8,7 +8,7 @@ use std::hash::Hash;
 use std::iter::{Product, Sum};
 use std::ops::Index;
 
-use rustc_hash::{FxHashMap, FxHashSet};
+use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};
 use rustc_macros::{Decodable_NoContext, Encodable_NoContext};
 
 use crate::fingerprint::Fingerprint;
@@ -241,10 +241,10 @@ pub struct UnordSet<V: Eq + Hash> {
 
 impl<V: Eq + Hash> UnordCollection for UnordSet<V> {}
 
-impl<V: Eq + Hash> Default for UnordSet<V> {
+impl<V: Eq + Hash> const Default for UnordSet<V> {
     #[inline]
     fn default() -> Self {
-        Self { inner: FxHashSet::default() }
+        Self { inner: FxHashSet::with_hasher(FxBuildHasher) }
     }
 }
 
@@ -438,10 +438,10 @@ pub struct UnordMap<K: Eq + Hash, V> {
 
 impl<K: Eq + Hash, V> UnordCollection for UnordMap<K, V> {}
 
-impl<K: Eq + Hash, V> Default for UnordMap<K, V> {
+impl<K: Eq + Hash, V> const Default for UnordMap<K, V> {
     #[inline]
     fn default() -> Self {
-        Self { inner: FxHashMap::default() }
+        Self { inner: FxHashMap::with_hasher(FxBuildHasher) }
     }
 }
 

compiler/rustc_hir/src/definitions.rs

@@ -103,7 +103,7 @@ pub struct DisambiguatorState {
 }
 
 impl DisambiguatorState {
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self { next: Default::default() }
     }