Also need to pad out "C-like" enum consts (paths as well as calls).

src/librustc/middle/trans/consts.rs

@@ -434,7 +434,13 @@ pub fn const_expr(cx: @crate_ctxt, e: @ast::expr) -> ValueRef {
                     let lldiscrim = base::get_discrim_val(cx, e.span,
                                                           enum_did,
                                                           variant_did);
-                    C_struct(~[lldiscrim])
+                    // However, we still have to pad it out to the
+                    // size of the full enum; see the expr_call case,
+                    // below.
+                    let ety = ty::expr_ty(cx.tcx, e);
+                    let size = machine::static_size_of_enum(cx, ety);
+                    let padding = C_null(T_array(T_i8(), size));
+                    C_struct(~[lldiscrim, padding])
                 }
                 Some(ast::def_struct(_)) => {
                     let ety = ty::expr_ty(cx.tcx, e);

src/test/run-pass/const-enum-tuple2.rs

@@ -0,0 +1,18 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+enum E { V0, V16(u16) }
+const C: (E, u16, u16) = (V0, 0x600D, 0xBAD);
+
+fn main() {
+    let (_, n, _) = C;
+    assert n != 0xBAD;
+    assert n == 0x600D;
+}