don't double-apply variant padding to const enums

Fixes #38002.

src/librustc_trans/adt.rs

@@ -688,9 +688,8 @@ pub fn trans_const<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>, discr: D
             let lldiscr = C_integral(Type::from_integer(ccx, d), discr.0 as u64, true);
             let mut vals_with_discr = vec![lldiscr];
             vals_with_discr.extend_from_slice(vals);
-            let mut contents = build_const_struct(ccx, &variant,
-                &vals_with_discr[..]);
-            let needed_padding = l.size(dl).bytes() - variant.min_size.bytes();
+            let mut contents = build_const_struct(ccx, &variant, &vals_with_discr[..]);
+            let needed_padding = l.size(dl).bytes() - variant.stride().bytes();
             if needed_padding > 0 {
                 contents.push(padding(ccx, needed_padding));
             }
@@ -703,8 +702,7 @@ pub fn trans_const<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>, discr: D
         }
         layout::Univariant { ref variant, .. } => {
             assert_eq!(discr, Disr(0));
-            let contents = build_const_struct(ccx,
-                &variant, vals);
+            let contents = build_const_struct(ccx, &variant, vals);
             C_struct(ccx, &contents[..], variant.packed)
         }
         layout::Vector { .. } => {
@@ -721,17 +719,15 @@ pub fn trans_const<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>, discr: D
         }
         layout::StructWrappedNullablePointer { ref nonnull, nndiscr, .. } => {
             if discr.0 == nndiscr {
-                C_struct(ccx, &build_const_struct(ccx, &nonnull, vals),
-                         false)
+                C_struct(ccx, &build_const_struct(ccx, &nonnull, vals), false)
             } else {
                 let fields = compute_fields(ccx, t, nndiscr as usize, false);
                 let vals = fields.iter().map(|&ty| {
                     // Always use null even if it's not the `discrfield`th
                     // field; see #8506.
                     C_null(type_of::sizing_type_of(ccx, ty))
                 }).collect::<Vec<ValueRef>>();
-                C_struct(ccx, &build_const_struct(ccx, &nonnull, &vals[..]),
-                         false)
+                C_struct(ccx, &build_const_struct(ccx, &nonnull, &vals[..]), false)
             }
         }
         _ => bug!("trans_const: cannot handle type {} repreented as {:#?}", t, l)

src/test/run-pass/issue-38002.rs

@@ -0,0 +1,45 @@
+// Copyright 2016 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.
+
+// Check that constant ADTs are translated OK, part k of N.
+
+#![feature(slice_patterns)]
+
+enum Bar {
+    C
+}
+
+enum Foo {
+    A {},
+    B {
+        y: usize,
+        z: Bar
+    },
+}
+
+const LIST: [(usize, Foo); 2] = [
+    (51, Foo::B { y: 42, z: Bar::C }),
+    (52, Foo::B { y: 45, z: Bar::C }),
+];
+
+pub fn main() {
+    match LIST {
+        [
+            (51, Foo::B { y: 42, z: Bar::C }),
+            (52, Foo::B { y: 45, z: Bar::C })
+        ] => {}
+        _ => {
+            // I would want to print the enum here, but if
+            // the discriminant is garbage this causes an
+            // `unreachable` and silent process exit.
+            panic!("trivial match failed")
+        }
+    }
+}