diff --git a/gcc/rust/util/rust-hir-map.cc b/gcc/rust/util/rust-hir-map.cc
index 65981095e699..7315edb2fb8f 100644
--- a/gcc/rust/util/rust-hir-map.cc
+++ b/gcc/rust/util/rust-hir-map.cc
@@ -1258,5 +1258,24 @@ Mappings::lookup_trait_item_lang_item (LangItem::Kind item, location_t locus)
   return lookup_trait_item_defid (trait_item_id);
 }
 
+void
+Mappings::insert_lang_item (LangItem::Kind item_type, DefId id)
+{
+  auto it = lang_item_mappings.find (item_type);
+  rust_assert (it == lang_item_mappings.end ());
+
+  lang_item_mappings[item_type] = id;
+}
+
+tl::optional<DefId &>
+Mappings::lookup_lang_item (LangItem::Kind item_type)
+{
+  auto it = lang_item_mappings.find (item_type);
+  if (it == lang_item_mappings.end ())
+    return tl::nullopt;
+
+  return it->second;
+}
+
 } // namespace Analysis
 } // namespace Rust
diff --git a/gcc/rust/util/rust-hir-map.h b/gcc/rust/util/rust-hir-map.h
index c07f254a020d..10ca71c57b69 100644
--- a/gcc/rust/util/rust-hir-map.h
+++ b/gcc/rust/util/rust-hir-map.h
@@ -256,22 +256,8 @@ class Mappings
     return it->second;
   }
 
-  void insert_lang_item (LangItem::Kind item_type, DefId id)
-  {
-    auto it = lang_item_mappings.find (item_type);
-    rust_assert (it == lang_item_mappings.end ());
-
-    lang_item_mappings[item_type] = id;
-  }
-
-  tl::optional<DefId &> lookup_lang_item (LangItem::Kind item_type)
-  {
-    auto it = lang_item_mappings.find (item_type);
-    if (it == lang_item_mappings.end ())
-      return tl::nullopt;
-
-    return it->second;
-  }
+  void insert_lang_item (LangItem::Kind item_type, DefId id);
+  tl::optional<DefId &> lookup_lang_item (LangItem::Kind item_type);
 
   // This will fatal_error when this lang item does not exist
   DefId get_lang_item (LangItem::Kind item_type, location_t locus);
diff --git a/gcc/rust/util/rust-lang-item.h b/gcc/rust/util/rust-lang-item.h
index 414436f0c965..bcf41df559e5 100644
--- a/gcc/rust/util/rust-lang-item.h
+++ b/gcc/rust/util/rust-lang-item.h
@@ -23,12 +23,12 @@
 
 namespace Rust {
 
-// https://github.com/rust-lang/rust/blob/master/library/core/src/ops/arith.rs
 class LangItem
 {
 public:
   enum class Kind
   {
+    // https://github.com/rust-lang/rust/blob/master/library/core/src/ops/arith.rs
     ADD,
     SUBTRACT,
     MULTIPLY,