Factor out some repeated code in parse_item_impl.

Author: nnethercote

compiler/rustc_parse/src/parser/item.rs

@@ -646,7 +646,7 @@ impl<'a> Parser<'a> {
 
         let impl_items = self.parse_item_list(attrs, |p| p.parse_impl_item(ForceCollect::No))?;
 
-        let item_kind = match ty_second {
+        let (of_trait, self_ty) = match ty_second {
             Some(ty_second) => {
                 // impl Trait for Type
                 if !has_for {
@@ -679,31 +679,20 @@ impl<'a> Parser<'a> {
                 };
                 let trait_ref = TraitRef { path, ref_id: ty_first.id };
 
-                ItemKind::Impl(Box::new(Impl {
-                    safety,
-                    polarity,
-                    defaultness,
-                    constness,
-                    generics,
-                    of_trait: Some(trait_ref),
-                    self_ty: ty_second,
-                    items: impl_items,
-                }))
-            }
-            None => {
-                // impl Type
-                ItemKind::Impl(Box::new(Impl {
-                    safety,
-                    polarity,
-                    defaultness,
-                    constness,
-                    generics,
-                    of_trait: None,
-                    self_ty: ty_first,
-                    items: impl_items,
-                }))
+                (Some(trait_ref), ty_second)
             }
+            None => (None, ty_first), // impl Type
         };
+        let item_kind = ItemKind::Impl(Box::new(Impl {
+            safety,
+            polarity,
+            defaultness,
+            constness,
+            generics,
+            of_trait,
+            self_ty,
+            items: impl_items,
+        }));
 
         Ok((Ident::empty(), item_kind))
     }