src/test/mir-opt/basic_assignment.rs

   1 // Copyright 2017 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 // this tests move up progration, which is not yet implemented
  12 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
  13 // file at the top-level directory of this distribution and at
  14 // http://rust-lang.org/COPYRIGHT.
  15 //
  16 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
  17 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
  18 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
  19 // option. This file may not be copied, modified, or distributed
  20 // except according to those terms.
  21
  22 // Check codegen for assignments (`a = b`) where the left-hand-side is
  23 // not yet initialized. Assignments tend to be absent in simple code,
  24 // so subtle breakage in them can leave a quite hard-to-find trail of
  25 // destruction.
  26
  27 // ignore-tidy-linelength
  28
  29 fn main() {
  30     let nodrop_x = false;
  31     let nodrop_y;
  32
  33     // Since boolean does not require drop, this can be a simple
  34     // assignment:
  35     nodrop_y = nodrop_x;
  36
  37     let drop_x : Option<Box<u32>> = None;
  38     let drop_y;
  39
  40     // Since the type of `drop_y` has drop, we generate a `replace`
  41     // terminator:
  42     drop_y = drop_x;
  43 }
  44
  45 // END RUST SOURCE
  46 // START rustc.main.SimplifyCfg-initial.after.mir
  47 //    bb0: {
  48 //        StorageLive(_1);
  49 //        _1 = const false;
  50 //        FakeRead(ForLet, _1);
  51 //        StorageLive(_2);
  52 //        StorageLive(_3);
  53 //        _3 = _1;
  54 //        _2 = move _3;
  55 //        StorageDead(_3);
  56 //        StorageLive(_4);
  57 //        _4 = std::option::Option<std::boxed::Box<u32>>::None;
  58 //        FakeRead(ForLet, _4);
  59 //        AscribeUserType(_4, o, UserTypeProjection { base: Ty(Canonical { variables: [], value: std::option::Option<std::boxed::Box<u32>> }), projs: [] });
  60 //        StorageLive(_5);
  61 //        StorageLive(_6);
  62 //        _6 = move _4;
  63 //        replace(_5 <- move _6) -> [return: bb2, unwind: bb5];
  64 //    }
  65 //    ...
  66 //    bb2: {
  67 //        drop(_6) -> [return: bb6, unwind: bb4];
  68 //    }
  69 //    ...
  70 //    bb5: {
  71 //        drop(_6) -> bb4;
  72 //    }
  73 // END rustc.main.SimplifyCfg-initial.after.mir