Add an is_marker flag to TraitDef

Author: scottmcm

src/librustc/ich/impls_ty.rs

@@ -1033,6 +1033,7 @@ impl_stable_hash_for!(struct ty::TraitDef {
     unsafety,
     paren_sugar,
     has_auto_impl,
+    is_marker,
     def_path_hash,
 });
 

src/librustc/ty/trait_def.rs

@@ -36,6 +36,11 @@ pub struct TraitDef {
 
     pub has_auto_impl: bool,
 
+    /// If `true`, then this trait has the `#[marker]` attribute, indicating
+    /// that all its associated items have defaults that cannot be overridden,
+    /// and thus `impl`s of it are allowed to overlap.
+    pub is_marker: bool,
+
     /// The ICH of this trait's DefPath, cached here so it doesn't have to be
     /// recomputed all the time.
     pub def_path_hash: DefPathHash,
@@ -53,13 +58,15 @@ impl<'a, 'gcx, 'tcx> TraitDef {
                unsafety: hir::Unsafety,
                paren_sugar: bool,
                has_auto_impl: bool,
+               is_marker: bool,
                def_path_hash: DefPathHash)
                -> TraitDef {
         TraitDef {
             def_id,
-            paren_sugar,
             unsafety,
+            paren_sugar,
             has_auto_impl,
+            is_marker,
             def_path_hash,
         }
     }

src/librustc_metadata/decoder.rs

@@ -539,6 +539,7 @@ impl<'a, 'tcx> CrateMetadata {
                           data.unsafety,
                           data.paren_sugar,
                           data.has_auto_impl,
+                          data.is_marker,
                           self.def_path_table.def_path_hash(item_id))
     }
 

src/librustc_metadata/encoder.rs

@@ -1152,6 +1152,7 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
                     unsafety: trait_def.unsafety,
                     paren_sugar: trait_def.paren_sugar,
                     has_auto_impl: tcx.trait_is_auto(def_id),
+                    is_marker: trait_def.is_marker,
                     super_predicates: self.lazy(&tcx.super_predicates_of(def_id)),
                 };
 

src/librustc_metadata/schema.rs

@@ -472,13 +472,15 @@ pub struct TraitData<'tcx> {
     pub unsafety: hir::Unsafety,
     pub paren_sugar: bool,
     pub has_auto_impl: bool,
+    pub is_marker: bool,
     pub super_predicates: Lazy<ty::GenericPredicates<'tcx>>,
 }
 
 impl_stable_hash_for!(struct TraitData<'tcx> {
     unsafety,
     paren_sugar,
     has_auto_impl,
+    is_marker,
     super_predicates
 });
 

src/librustc_typeck/collect.rs

@@ -735,8 +735,10 @@ fn trait_def<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx ty::
         err.emit();
     }
 
+    let is_marker = false; // FIXME (scottmcm)
+
     let def_path_hash = tcx.def_path_hash(def_id);
-    let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, def_path_hash);
+    let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
     tcx.alloc_trait_def(def)
 }