Code up the new lifetime default rules, but leave them disabled

for now.

src/librustc/middle/ty.rs

@@ -2245,6 +2245,9 @@ pub enum ObjectLifetimeDefault {
     /// `T:'a` constraints are found.
     Ambiguous,
 
+    /// Use the base default, typically 'static, but in a fn body it is a fresh variable
+    BaseDefault,
+
     /// Use the given region as the default.
     Specific(Region),
 }
@@ -2256,7 +2259,7 @@ pub struct TypeParameterDef<'tcx> {
     pub space: subst::ParamSpace,
     pub index: u32,
     pub default: Option<Ty<'tcx>>,
-    pub object_lifetime_default: Option<ObjectLifetimeDefault>,
+    pub object_lifetime_default: ObjectLifetimeDefault,
 }
 
 #[derive(RustcEncodable, RustcDecodable, Clone, Debug)]
@@ -7328,6 +7331,7 @@ impl<'tcx> fmt::Debug for ObjectLifetimeDefault {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
             ObjectLifetimeDefault::Ambiguous => write!(f, "Ambiguous"),
+            ObjectLifetimeDefault::BaseDefault => format!("BaseDefault"),
             ObjectLifetimeDefault::Specific(ref r) => write!(f, "{:?}", r),
         }
     }

src/librustc/middle/ty_fold.rs

@@ -369,6 +369,9 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ObjectLifetimeDefault {
             ty::ObjectLifetimeDefault::Ambiguous =>
                 ty::ObjectLifetimeDefault::Ambiguous,
 
+            ty::ObjectLifetimeDefault::BaseDefault =>
+                ty::ObjectLifetimeDefault::BaseDefault,
+
             ty::ObjectLifetimeDefault::Specific(r) =>
                 ty::ObjectLifetimeDefault::Specific(r.fold_with(folder)),
         }