Fix some cross crate existential type ICEs

src/librustc_metadata/decoder.rs

@@ -893,6 +893,9 @@ impl<'a, 'tcx> CrateMetadata {
             EntryKind::AssociatedType(container) => {
                 (ty::AssociatedKind::Type, container, false)
             }
+            EntryKind::AssociatedExistential(container) => {
+                (ty::AssociatedKind::Existential, container, false)
+            }
             _ => bug!("cannot get associated-item of `{:?}`", def_key)
         };
 

src/librustc_resolve/build_reduced_graph.rs

@@ -680,6 +680,7 @@ impl<'a> Resolver<'a> {
                 }
                 module.populated.set(true);
             }
+            Def::Existential(..) |
             Def::TraitAlias(..) => {
                 self.define(parent, ident, TypeNS, (def, vis, DUMMY_SP, expansion));
             }

src/librustc_typeck/check/wfcheck.rs

@@ -608,8 +608,8 @@ fn check_existential_types<'a, 'fcx, 'gcx, 'tcx>(
             if let ty::Opaque(def_id, substs) = ty.sty {
                 trace!("check_existential_types: opaque_ty, {:?}, {:?}", def_id, substs);
                 let generics = tcx.generics_of(def_id);
-                // only check named existential types
-                if generics.parent.is_none() {
+                // only check named existential types defined in this crate
+                if generics.parent.is_none() && def_id.is_local() {
                     let opaque_node_id = tcx.hir().as_local_node_id(def_id).unwrap();
                     if may_define_existential_type(tcx, fn_def_id, opaque_node_id) {
                         trace!("check_existential_types may define. Generics: {:#?}", generics);

src/test/ui/existential_types/auxiliary/cross_crate_ice.rs

@@ -0,0 +1,13 @@
+// Crate that exports an existential type. Used for testing cross-crate.
+
+#![feature(const_fn)]
+#![crate_type="rlib"]
+
+#![feature(existential_type)]
+
+pub existential type Foo: std::fmt::Debug;
+
+pub fn foo() -> Foo {
+    5
+}
+

src/test/ui/existential_types/auxiliary/cross_crate_ice2.rs

@@ -0,0 +1,22 @@
+// Crate that exports an existential type. Used for testing cross-crate.
+
+#![feature(const_fn)]
+#![crate_type="rlib"]
+
+#![feature(existential_type)]
+
+pub trait View {
+    type Tmp: Iterator<Item = u32>;
+
+    fn test(&self) -> Self::Tmp;
+}
+
+pub struct X;
+
+impl View for X {
+    existential type Tmp: Iterator<Item = u32>;
+
+    fn test(&self) -> Self::Tmp {
+        vec![1,2,3].into_iter()
+    }
+}

src/test/ui/existential_types/cross_crate_ice.rs

@@ -0,0 +1,16 @@
+// aux-build:cross_crate_ice.rs
+// compile-pass
+
+extern crate cross_crate_ice;
+
+struct Bar(cross_crate_ice::Foo);
+
+impl Bar {
+    fn zero(&self) -> &cross_crate_ice::Foo {
+        &self.0
+    }
+}
+
+fn main() {
+    let _ = cross_crate_ice::foo();
+}

src/test/ui/existential_types/cross_crate_ice2.rs

@@ -0,0 +1,11 @@
+// aux-build:cross_crate_ice2.rs
+// compile-pass
+
+extern crate cross_crate_ice2;
+
+use cross_crate_ice2::View;
+
+fn main() {
+    let v = cross_crate_ice2::X;
+    v.test();
+}