Mark features as part of the 2018 preview

Author: Manishearth

src/libsyntax/feature_gate.rs

@@ -397,7 +397,7 @@ declare_features! (
     (active, generic_associated_types, "1.23.0", Some(44265), None),
 
     // Resolve absolute paths as paths from other crates
-    (active, extern_absolute_paths, "1.24.0", Some(44660), None),
+    (active, extern_absolute_paths, "1.24.0", Some(44660), Some(Edition::Edition2018)),
 
     // `foo.rs` as an alternative to `foo/mod.rs`
     (active, non_modrs_mods, "1.24.0", Some(44660), Some(Edition::Edition2018)),
@@ -468,7 +468,7 @@ declare_features! (
     (active, doc_alias, "1.27.0", Some(50146), None),
 
     // Access to crate names passed via `--extern` through prelude
-    (active, extern_prelude, "1.27.0", Some(44660), None),
+    (active, extern_prelude, "1.27.0", Some(44660), Some(Edition::Edition2018)),
 );
 
 declare_features! (

src/test/run-make-fulldeps/extern-prelude/inner-mod.rs

@@ -11,7 +11,9 @@
 // Modules that clash with crates don't hit feature errors when
 // the feature is disabled
 
+extern crate ep_lib;
+
 fn main() {
     let s = ep_lib::S;
-    s.internal(); // OK
+    s.external(); // OK
 }