Consider slices to be a structural type. Closes #2748.

src/rustc/middle/trans/base.rs

@@ -1369,7 +1369,7 @@ fn copy_val_no_check(bcx: block, action: copy_action, dst: ValueRef,
     let _icx = bcx.insn_ctxt("copy_val_no_check");
     let ccx = bcx.ccx();
     let mut bcx = bcx;
-    if ty::type_is_scalar(t) || ty::type_is_slice(t) {
+    if ty::type_is_scalar(t) {
         Store(bcx, src, dst);
         ret bcx;
     }
@@ -1401,7 +1401,7 @@ fn move_val(cx: block, action: copy_action, dst: ValueRef,
     let mut src_val = src.val;
     let tcx = cx.tcx();
     let mut cx = cx;
-    if ty::type_is_scalar(t) || ty::type_is_slice(t) {
+    if ty::type_is_scalar(t) {
         if src.kind == owned { src_val = Load(cx, src_val); }
         Store(cx, src_val, dst);
         ret cx;

src/rustc/middle/ty.rs

@@ -1074,8 +1074,10 @@ fn type_is_bool(ty: t) -> bool { get(ty).struct == ty_bool }
 fn type_is_structural(ty: t) -> bool {
     alt get(ty).struct {
       ty_rec(_) | ty_class(*) | ty_tup(_) | ty_enum(*) | ty_fn(_) |
-      ty_trait(*) | ty_evec(_, vstore_fixed(_))
-      | ty_estr(vstore_fixed(_)) { true }
+      ty_trait(*) |
+      ty_evec(_, vstore_fixed(_)) | ty_estr(vstore_fixed(_)) |
+      ty_evec(_, vstore_slice(_)) | ty_estr(vstore_slice(_))
+      { true }
       _ { false }
     }
 }

src/test/run-pass/issue-2748-a.rs

+class CMap/& {
+    let buf: [u8]/&;
+
+    new(buf: [u8]/&) {
+        self.buf = buf;
+    }
+}
+
+fn main() { }

src/test/run-pass/issue-2748-b.rs

+fn thing(x: &[int]) -> &[int] { x }
+fn main() {
+    let x = &[1,2,3];
+    let y = x;
+    let z = thing(x);
+    assert(z[2] == x[2]);
+    assert(z[1] == y[1]);
+}