Merge branch 'refactor-select' of https://github.com/aravind-pg/rust into update...

[rust.git] / src / librustc_typeck / check / wfcheck.rs

diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index 258860d3d5e404deb844b8d673fc62c1c258fbee..d10ee358e072846e77be1591c47c141b1f55d4b1 100644 (file)
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -363,13 +363,19 @@ fn check_where_clauses<'fcx, 'tcx>(&mut self,
         let generics = self.tcx.generics_of(def_id);
         let is_our_default = |def: &ty::TypeParameterDef|
                                 def.has_default && def.index >= generics.parent_count() as u32;
-        let defaulted_params = generics.types.iter().cloned().filter(&is_our_default);
-        // Check that defaults are well-formed. See test `type-check-defaults.rs`.
+
+        // Check that concrete defaults are well-formed. See test `type-check-defaults.rs`.
         // For example this forbids the declaration:
         // struct Foo<T = Vec<[u32]>> { .. }
         // Here the default `Vec<[u32]>` is not WF because `[u32]: Sized` does not hold.
-        for d in defaulted_params.map(|p| p.def_id) {
-            fcx.register_wf_obligation(fcx.tcx.type_of(d), fcx.tcx.def_span(d), self.code.clone());
+        for d in generics.types.iter().cloned().filter(is_our_default).map(|p| p.def_id) {
+            let ty = fcx.tcx.type_of(d);
+            // ignore dependent defaults -- that is, where the default of one type
+            // parameter includes another (e.g., <T, U = T>). In those cases, we can't
+            // be sure if it will error or not as user might always specify the other.
+            if !ty.needs_subst() {
+                fcx.register_wf_obligation(ty, fcx.tcx.def_span(d), self.code.clone());
+            }
         }
 
         // Check that trait predicates are WF when params are substituted by their defaults.
@@ -530,7 +536,7 @@ fn check_method_receiver<'fcx, 'tcx>(&mut self,
         let is_self_ty = |ty| fcx.infcx.can_eq(fcx.param_env, self_ty, ty).is_ok();
         let self_kind = ExplicitSelf::determine(self_arg_ty, is_self_ty);
 
-        if !fcx.tcx.sess.features.borrow().arbitrary_self_types {
+        if !fcx.tcx.features().arbitrary_self_types {
             match self_kind {
                 ExplicitSelf::ByValue |
                 ExplicitSelf::ByReference(_, _) |