src/test/run-pass/diverging-fallback-option.rs

   1 // Copyright 2012 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 #![allow(warnings)]
  12
  13 // Here the type of `c` is `Option<?T>`, where `?T` is unconstrained.
  14 // Because there is data-flow from the `{ return; }` block, which
  15 // diverges and hence has type `!`, into `c`, we will default `?T` to
  16 // `!`, and hence this code compiles rather than failing and requiring
  17 // a type annotation.
  18
  19 fn main() {
  20     let c = Some({ return; });
  21     c.unwrap();
  22 }