rustc: qualify expressions in check_const for potential promotion.

src/librustc/diagnostics.rs

@@ -59,6 +59,7 @@
     E0010,
     E0011,
     E0012,
+    E0013,
     E0014,
     E0015,
     E0016,

src/librustc/metadata/common.rs

@@ -143,6 +143,7 @@ pub enum astencode_tag { // Reserves 0x40 -- 0x5f
     tag_table_upvar_capture_map = 0x56,
     tag_table_capture_modes = 0x57,
     tag_table_object_cast_map = 0x58,
+    tag_table_const_qualif = 0x59,
 }
 
 pub const tag_item_trait_item_sort: uint = 0x60;

src/librustc/middle/astencode.rs

@@ -23,6 +23,7 @@
 use metadata::tydecode::{DefIdSource, NominalType, TypeWithId, TypeParameter};
 use metadata::tydecode::{RegionParameter, ClosureSource};
 use metadata::tyencode;
+use middle::check_const::ConstQualif;
 use middle::mem_categorization::Typer;
 use middle::subst;
 use middle::subst::VecPerParamSpace;
@@ -1306,6 +1307,15 @@ fn encode_side_tables_for_id(ecx: &e::EncodeContext,
             })
         })
     }
+
+    for &qualif in tcx.const_qualif_map.borrow().get(&id).iter() {
+        rbml_w.tag(c::tag_table_const_qualif, |rbml_w| {
+            rbml_w.id(id);
+            rbml_w.tag(c::tag_table_val, |rbml_w| {
+                qualif.encode(rbml_w).unwrap()
+            })
+        })
+    }
 }
 
 trait doc_decoder_helpers {
@@ -1920,6 +1930,10 @@ fn decode_side_tables(dcx: &DecodeContext,
                         dcx.tcx.closure_kinds.borrow_mut().insert(ast_util::local_def(id),
                                                                   closure_kind);
                     }
+                    c::tag_table_const_qualif => {
+                        let qualif: ConstQualif = Decodable::decode(val_dsr).unwrap();
+                        dcx.tcx.const_qualif_map.borrow_mut().insert(id, qualif);
+                    }
                     _ => {
                         dcx.tcx.sess.bug(
                             &format!("unknown tag found in side tables: {:x}",

src/librustc/middle/ty.rs

@@ -44,6 +44,7 @@
 use lint;
 use metadata::csearch;
 use middle;
+use middle::check_const;
 use middle::const_eval;
 use middle::def::{self, DefMap, ExportMap};
 use middle::dependency_format;
@@ -838,6 +839,9 @@ pub struct ctxt<'tcx> {
 
     /// Caches whether traits are object safe
     pub object_safety_cache: RefCell<DefIdMap<bool>>,
+
+    /// Maps Expr NodeId's to their constant qualification.
+    pub const_qualif_map: RefCell<NodeMap<check_const::ConstQualif>>,
 }
 
 // Flags that we track on types. These flags are propagated upwards
@@ -2472,6 +2476,7 @@ pub fn mk_ctxt<'tcx>(s: Session,
         type_impls_copy_cache: RefCell::new(HashMap::new()),
         type_impls_sized_cache: RefCell::new(HashMap::new()),
         object_safety_cache: RefCell::new(DefIdMap()),
+        const_qualif_map: RefCell::new(NodeMap()),
    }
 }