Two minor changes for readability and efficiency

Author: FabianWolff

compiler/rustc_passes/src/lang_items.rs

@@ -100,12 +100,11 @@ impl LanguageItemCollector<'tcx> {
     }
 
     fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
-        let lang_item = LangItem::from_u32(item_index as u32).unwrap();
-        let name = lang_item.name();
-
         // Check for duplicates.
         if let Some(original_def_id) = self.items.items[item_index] {
             if original_def_id != item_def_id {
+                let lang_item = LangItem::from_u32(item_index as u32).unwrap();
+                let name = lang_item.name();
                 let mut err = match self.tcx.hir().span_if_local(item_def_id) {
                     Some(span) => struct_span_err!(
                         self.tcx.sess,

compiler/rustc_typeck/src/check/mod.rs

@@ -1194,13 +1194,10 @@ fn potentially_plural_count(count: usize, word: &str) -> String {
 fn has_expected_num_generic_args<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_did: Option<DefId>,
-    mut expected: usize,
+    expected: usize,
 ) -> bool {
     trait_did.map_or(true, |trait_did| {
         let generics = tcx.generics_of(trait_did);
-        if generics.has_self {
-            expected += 1;
-        }
-        generics.count() == expected
+        generics.count() == expected + if generics.has_self { 1 } else { 0 }
     })
 }