hir: replace `lazy_static` by `SyncLazy` from std

Cargo.lock

@@ -3530,7 +3530,6 @@ version = "0.0.0"
 name = "rustc_hir"
 version = "0.0.0"
 dependencies = [
- "lazy_static",
  "rustc_ast",
  "rustc_data_structures",
  "rustc_index",

compiler/rustc_hir/Cargo.toml

@@ -15,6 +15,5 @@ rustc_index = { path = "../rustc_index" }
 rustc_span = { path = "../rustc_span" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_ast = { path = "../rustc_ast" }
-lazy_static = "1"
 tracing = "0.1"
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }

compiler/rustc_hir/src/lang_items.rs

@@ -17,7 +17,7 @@
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
 
-use lazy_static::lazy_static;
+use std::lazy::SyncLazy;
 
 pub enum LangItemGroup {
     Op,
@@ -117,14 +117,12 @@ pub fn $method(&self) -> Option<DefId> {
             )*
         }
 
-        lazy_static! {
-            /// A mapping from the name of the lang item to its order and the form it must be of.
-            pub static ref ITEM_REFS: FxHashMap<Symbol, (usize, Target)> = {
-                let mut item_refs = FxHashMap::default();
-                $( item_refs.insert($name, (LangItem::$variant as usize, $target)); )*
-                item_refs
-            };
-        }
+        /// A mapping from the name of the lang item to its order and the form it must be of.
+        pub static ITEM_REFS: SyncLazy<FxHashMap<Symbol, (usize, Target)>> = SyncLazy::new(|| {
+            let mut item_refs = FxHashMap::default();
+            $( item_refs.insert($name, (LangItem::$variant as usize, $target)); )*
+            item_refs
+        });
 
 // End of the macro
     }

compiler/rustc_hir/src/lib.rs

@@ -6,6 +6,7 @@
 #![feature(const_fn)] // For the unsizing cast on `&[]`
 #![feature(const_panic)]
 #![feature(in_band_lifetimes)]
+#![feature(once_cell)]
 #![feature(or_patterns)]
 #![recursion_limit = "256"]
 

compiler/rustc_hir/src/weak_lang_items.rs

@@ -7,18 +7,16 @@
 use rustc_data_structures::fx::FxHashMap;
 use rustc_span::symbol::{sym, Symbol};
 
-use lazy_static::lazy_static;
+use std::lazy::SyncLazy;
 
 macro_rules! weak_lang_items {
     ($($name:ident, $item:ident, $sym:ident;)*) => (
 
-lazy_static! {
-    pub static ref WEAK_ITEMS_REFS: FxHashMap<Symbol, LangItem> = {
-        let mut map = FxHashMap::default();
-        $(map.insert(sym::$name, LangItem::$item);)*
-        map
-    };
-}
+pub static WEAK_ITEMS_REFS: SyncLazy<FxHashMap<Symbol, LangItem>> = SyncLazy::new(|| {
+    let mut map = FxHashMap::default();
+    $(map.insert(sym::$name, LangItem::$item);)*
+    map
+});
 
 /// The `check_name` argument avoids the need for `librustc_hir` to depend on
 /// `librustc_session`.