ICE: unexpected failure path, comparing in librustc/middle/trans/datum.rs

[DanielKeep]

Happens on WIndows 7 x64 with latest Rust 32-bit nightly.

rustc -v verbose:

rustc 0.12.0-pre-nightly (63eaba24d 2014-09-15 21:56:00 +0000)
binary: rustc
commit-hash: 63eaba24d6a7f93061d63337ea1f7083ca892787
commit-date: 2014-09-15 21:56:00 +0000
host: i686-w64-mingw32
release: 0.12.0-pre-nightly

(On a side note, is there any way to work out what the latest released nightly version is?)

test-ice.rs:

#[allow(dead_code)]
fn check(a: &str) {
    let x = a as *const str;
    x == x;
}

fn main() {
}

Compiling with rustc test-ice.rs produces:

error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
task 'rustc' failed at 'assertion failed: self.appropriate_rvalue_mode(bcx.ccx()) == ByValue', C:\bot\slave\nightly-win32\build\src\librustc\middle\trans\datum.rs:651

stack backtrace:
   1:   0x8ce8ae
   2: 0x62907a4c
   3: 0x6fcc51ae
   4: 0x700ae66f
   5: 0x700d3ea2
   6: 0x700c93a5
   7: 0x70085c94
   8: 0x70084ffe
   9: 0x7008482e
  10: 0x70085e38
  11: 0x7013635b
  12: 0x7007425e
  13: 0x7006fe4c
  14: 0x70140d38
  15: 0x70555cf9
  16: 0x7054f548
  17: 0x705f597a
  18: 0x705f38dd
  19: 0x6fcf8bde
  20: 0x6fcf8aef
  21: 0x6aeeb41c
  22: 0x62907375
  23: 0x62905506
  24: 0x6aeeb27a
  25: 0x62906fc2
  26: 0x779c9f72

#[allow(dead_code)] is there to suppress the warning, main can be removed if you compile the rest as a library. Also works if you substitute the expression for x directly and if you pass two &str arguments (the original use case).

The original intent was to tell if two &strs were identical as a sanity check.

[frewsxcv]

Can confirm this still results in an ICE.

rustc 1.0.0-nightly (522d09dfe 2015-02-19) (built 2015-02-19)
binary: rustc
commit-hash: 522d09dfecbeca1595f25ac58c6d0178bbd21d7d
commit-date: 2015-02-19
build-date: 2015-02-19
host: x86_64-apple-darwin
release: 1.0.0-nightly

[tamird]

Triage: still ICEs.

[arielb1]

cc rust-lang/rfcs#1135

[pmarcelll]

#28270 fixed this.

[frewsxcv]

I'll add a regression test for this