mir: Don't use ConstVal kinds that contain local NodeId's.

Author: eddyb

src/librustc_mir/hair/cx/mod.rs

@@ -84,9 +84,16 @@ impl<'a,'tcx:'a> Cx<'a, 'tcx> {
 
     pub fn try_const_eval_literal(&mut self, e: &hir::Expr) -> Option<Literal<'tcx>> {
         let hint = const_eval::EvalHint::ExprTypeChecked;
-        const_eval::eval_const_expr_partial(self.tcx, e, hint, None)
-            .ok()
-            .map(|v| Literal::Value { value: v })
+        const_eval::eval_const_expr_partial(self.tcx, e, hint, None).ok().and_then(|v| {
+            match v {
+                // All of these contain local IDs, unsuitable for storing in MIR.
+                ConstVal::Struct(_) | ConstVal::Tuple(_) |
+                ConstVal::Array(..) | ConstVal::Repeat(..) |
+                ConstVal::Function(_) => None,
+
+                _ => Some(Literal::Value { value: v })
+            }
+        })
     }
 
     pub fn num_variants(&mut self, adt_def: ty::AdtDef<'tcx>) -> usize {

src/librustc_trans/trans/mir/constant.rs

@@ -15,7 +15,7 @@ use rustc_const_eval::ConstInt::*;
 use rustc::mir::repr as mir;
 use trans::abi;
 use trans::common::{self, BlockAndBuilder, C_bool, C_bytes, C_floating_f64, C_integral,
-                    C_str_slice, C_nil, C_undef};
+                    C_str_slice, C_undef};
 use trans::consts;
 use trans::expr;
 use trans::inline;
@@ -85,16 +85,13 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
             ConstVal::Integral(InferSigned(v)) => C_integral(llty, v as u64, true),
             ConstVal::Str(ref v) => C_str_slice(ccx, v.clone()),
             ConstVal::ByteStr(ref v) => consts::addr_of(ccx, C_bytes(ccx, v), 1, "byte_str"),
-            ConstVal::Struct(id) | ConstVal::Tuple(id) |
-            ConstVal::Array(id, _) | ConstVal::Repeat(id, _) => {
-                let expr = bcx.tcx().map.expect_expr(id);
-                bcx.with_block(|bcx| {
-                    expr::trans(bcx, expr).datum.val
-                })
-            },
+            ConstVal::Struct(_) | ConstVal::Tuple(_) |
+            ConstVal::Array(..) | ConstVal::Repeat(..) |
+            ConstVal::Function(_) => {
+                unreachable!("MIR must not use {:?} (which refers to a local ID)", cv)
+            }
             ConstVal::Char(c) => C_integral(Type::char(ccx), c as u64, false),
             ConstVal::Dummy => unreachable!(),
-            ConstVal::Function(_) => C_nil(ccx)
         }
     }