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rustc: check instantiability of fixed length vectors properly. #11661

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6 changes: 6 additions & 0 deletions src/librustc/middle/ty.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2287,6 +2287,12 @@ pub fn is_instantiable(cx: ctxt, r_ty: t) -> bool {
::util::ppaux::ty_to_str(cx, ty));

let r = match get(ty).sty {
// fixed length vectors need special treatment compared to
// normal vectors, since they don't necessarily have the
// possibilty to have length zero.
ty_vec(_, vstore_fixed(0)) => false, // don't need no contents
ty_vec(mt, vstore_fixed(_)) => type_requires(cx, seen, r_ty, mt.ty),

ty_nil |
ty_bot |
ty_bool |
Expand Down
26 changes: 26 additions & 0 deletions src/test/compile-fail/uninstantiable-fixed-length-vec.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
// Copyright 2014 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.

// issue #11659, the compiler needs to know that a fixed length vector
// always requires instantiable contents to instantiable itself
// (unlike a ~[] vector which can have length zero).

// ~ to avoid infinite size.
struct Uninstantiable { //~ ERROR cannot be instantiated without an instance of itself
p: ~[Uninstantiable, .. 1]
}

struct Instantiable { p: ~[Instantiable, .. 0] }


fn main() {
let _ = None::<Uninstantiable>;
let _ = Instantiable { p: ~([]) };
}