src/test/compile-fail/unboxed-closures-mutate-upvar.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Test that we cannot mutate an outer variable that is not declared
  12 // as `mut` through a closure. Also test that we CAN mutate a moved copy,
  13 // unless this is a `Fn` closure. Issue #16749.
  14
  15 #![feature(unboxed_closures)]
  16
  17 use std::mem;
  18
  19 fn to_fn<A,F:Fn<A>>(f: F) -> F { f }
  20 fn to_fn_mut<A,F:FnMut<A>>(f: F) -> F { f }
  21
  22 fn a() {
  23     let n = 0u8;
  24     let mut f = to_fn_mut(|| { //~ ERROR closure cannot assign
  25         n += 1;
  26     });
  27 }
  28
  29 fn b() {
  30     let mut n = 0u8;
  31     let mut f = to_fn_mut(|| {
  32         n += 1; // OK
  33     });
  34 }
  35
  36 fn c() {
  37     let n = 0u8;
  38     let mut f = to_fn_mut(move || {
  39         // If we just did a straight-forward desugaring, this would
  40         // compile, but we do something a bit more subtle, and hence
  41         // we get an error.
  42         n += 1; //~ ERROR cannot assign
  43     });
  44 }
  45
  46 fn d() {
  47     let mut n = 0u8;
  48     let mut f = to_fn_mut(move || {
  49         n += 1; // OK
  50     });
  51 }
  52
  53 fn e() {
  54     let n = 0u8;
  55     let mut f = to_fn(move || {
  56         n += 1; //~ ERROR cannot assign
  57     });
  58 }
  59
  60 fn f() {
  61     let mut n = 0u8;
  62     let mut f = to_fn(move || {
  63         n += 1; //~ ERROR cannot assign
  64     });
  65 }
  66
  67 fn main() { }