factor variances into a proper query

[rust.git] / src / librustc_typeck / variance / terms.rs

diff --git a/src/librustc_typeck/variance/terms.rs b/src/librustc_typeck/variance/terms.rs
index 61ff154e458d381f651ffc67e4bc75d8dece8725..3f4b15e35a42db30d6019df2c046ac3efcada97a 100644 (file)
--- a/src/librustc_typeck/variance/terms.rs
+++ b/src/librustc_typeck/variance/terms.rs
@@ -139,7 +139,6 @@ fn lang_items(tcx: TyCtxt) -> Vec<(ast::NodeId, Vec<ty::Variance>)> {
 impl<'a, 'tcx> TermsContext<'a, 'tcx> {
     fn add_inferreds_for_item(&mut self,
                               item_id: ast::NodeId,
-                              has_self: bool,
                               generics: &hir::Generics) {
         //! Add "inferreds" for the generic parameters declared on this
         //! item. This has a lot of annoying parameters because we are
@@ -149,38 +148,17 @@ fn add_inferreds_for_item(&mut self,
         //!
 
         // NB: In the code below for writing the results back into the
-        // tcx, we rely on the fact that all inferreds for a particular
-        // item are assigned continuous indices.
+        // `CrateVariancesMap`, we rely on the fact that all inferreds
+        // for a particular item are assigned continuous indices.
 
-        let inferreds_on_entry = self.num_inferred();
-
-        if has_self {
-            self.add_inferred(item_id, 0, item_id);
-        }
-
-        for (i, p) in generics.lifetimes.iter().enumerate() {
+        for (p, i) in generics.lifetimes.iter().zip(0..) {
             let id = p.lifetime.id;
-            let i = has_self as usize + i;
             self.add_inferred(item_id, i, id);
         }
 
-        for (i, p) in generics.ty_params.iter().enumerate() {
-            let i = has_self as usize + generics.lifetimes.len() + i;
+        for (p, i) in generics.ty_params.iter().zip(generics.lifetimes.len()..) {
             self.add_inferred(item_id, i, p.id);
         }
-
-        // If this item has no type or lifetime parameters,
-        // then there are no variances to infer, so just
-        // insert an empty entry into the variance map.
-        // Arguably we could just leave the map empty in this
-        // case but it seems cleaner to be able to distinguish
-        // "invalid item id" from "item id with no
-        // parameters".
-        if self.num_inferred() == inferreds_on_entry {
-            let item_def_id = self.tcx.hir.local_def_id(item_id);
-            self.tcx.maps.variances_of.borrow_mut()
-                .insert(item_def_id, self.empty_variances.clone());
-        }
     }
 
     fn add_inferred(&mut self, item_id: ast::NodeId, index: usize, param_id: ast::NodeId) {
@@ -232,15 +210,10 @@ fn visit_item(&mut self, item: &hir::Item) {
             hir::ItemEnum(_, ref generics) |
             hir::ItemStruct(_, ref generics) |
             hir::ItemUnion(_, ref generics) => {
-                self.add_inferreds_for_item(item.id, false, generics);
-            }
-            hir::ItemTrait(_, ref generics, ..) => {
-                // Note: all inputs for traits are ultimately
-                // constrained to be invariant. See `visit_item` in
-                // the impl for `ConstraintContext` in `constraints.rs`.
-                self.add_inferreds_for_item(item.id, true, generics);
+                self.add_inferreds_for_item(item.id, generics);
             }
 
+            hir::ItemTrait(..) |
             hir::ItemExternCrate(_) |
             hir::ItemUse(..) |
             hir::ItemDefaultImpl(..) |