None
},
+ // Perhaps one of the upvars of this struct is non-zero
+ // Let's recurse and find out!
+ ty::ty_closure(def_id, substs) => {
+ let typer = NormalizingClosureTyper::new(tcx);
+ let upvars = typer.closure_upvars(def_id, substs).unwrap();
+ let upvar_types = upvars.iter().map(|u| u.ty).collect::<Vec<_>>();
+
+ for (j, &ty) in upvar_types.iter().enumerate() {
+ if let Some(mut fpath) = find_discr_field_candidate(tcx, ty, path.clone()) {
+ fpath.push(j);
+ return Some(fpath);
+ }
+ }
+ None
+ },
+
// Can we use one of the fields in this tuple?
ty::ty_tup(ref tys) => {
for (j, &ty) in tys.iter().enumerate() {
--- /dev/null
+// Copyright 2015 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.
+
+
+use std::mem;
+
+pub fn main() {
+ // By Ref Capture
+ let a = 10i32;
+ let b = Some(|| println!("{}", a));
+ // When we capture by reference we can use any of the
+ // captures as the discriminant since they're all
+ // behind a pointer.
+ assert_eq!(mem::size_of_val(&b), mem::size_of::<usize>());
+
+ // By Value Capture
+ let a = Box::new(12i32);
+ let b = Some(move || println!("{}", a));
+ // We captured `a` by value and since it's a `Box` we can use it
+ // as the discriminant.
+ assert_eq!(mem::size_of_val(&b), mem::size_of::<Box<i32>>());
+
+ // By Value Capture - Transitive case
+ let a = "Hello".to_string(); // String -> Vec -> Unique -> NonZero
+ let b = Some(move || println!("{}", a));
+ // We captured `a` by value and since down the chain it contains
+ // a `NonZero` field, we can use it as the discriminant.
+ assert_eq!(mem::size_of_val(&b), mem::size_of::<String>());
+
+ // By Value - No Optimization
+ let a = 14i32;
+ let b = Some(move || println!("{}", a));
+ // We captured `a` by value but we can't use it as the discriminant
+ // thus we end up with an extra field for the discriminant
+ assert_eq!(mem::size_of_val(&b), mem::size_of::<(i32, i32)>());
+}