rustc_resolve: move extern_prelude from Resolver to Session.

1 files changed, 18 insertions, 1 deletions

diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index be347253e7f..20d4ba9c632 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -38,7 +38,7 @@ use syntax::parse;
 use syntax::parse::ParseSess;
 use syntax::{ast, source_map};
 use syntax::feature_gate::AttributeType;
-use syntax_pos::{MultiSpan, Span};
+use syntax_pos::{MultiSpan, Span, symbol::Symbol};
 use util::profiling::SelfProfiler;
 
 use rustc_target::spec::PanicStrategy;
@@ -168,6 +168,10 @@ pub struct Session {
 
     /// Cap lint level specified by a driver specifically.
     pub driver_lint_caps: FxHashMap<lint::LintId, lint::Level>,
+
+    /// All the crate names specified with `--extern`, and the builtin ones.
+    /// Starting with the Rust 2018 edition, absolute paths resolve in this set.
+    pub extern_prelude: FxHashSet<Symbol>,
 }
 
 pub struct PerfStats {
@@ -1126,6 +1130,18 @@ pub fn build_session_(
         CguReuseTracker::new_disabled()
     };
 
+
+    let mut extern_prelude: FxHashSet<Symbol> =
+        sopts.externs.iter().map(|kv| Symbol::intern(kv.0)).collect();
+
+    // HACK(eddyb) this ignores the `no_{core,std}` attributes.
+    // FIXME(eddyb) warn (somewhere) if core/std is used with `no_{core,std}`.
+    // if !attr::contains_name(&krate.attrs, "no_core") {
+    // if !attr::contains_name(&krate.attrs, "no_std") {
+    extern_prelude.insert(Symbol::intern("core"));
+    extern_prelude.insert(Symbol::intern("std"));
+    extern_prelude.insert(Symbol::intern("meta"));
+
     let sess = Session {
         target: target_cfg,
         host,
@@ -1201,6 +1217,7 @@ pub fn build_session_(
         has_global_allocator: Once::new(),
         has_panic_handler: Once::new(),
         driver_lint_caps: FxHashMap(),
+        extern_prelude,
     };
 
     validate_commandline_args_with_session_available(&sess);