internal compiler error: translating unsupported cast

[Kraxxis]

% rustc --version
rustc 1.1.0

The following minimal example will cause an internal compiler error:

fn main() {
    let x = String::new() as String;
}

Error text:

% RUST_BACKTRACE=1 rustc wat.rs
wat.rs:1:16: 1:17 warning: unused variable: `x`, #[warn(unused_variables)] on by default
wat.rs:1 fn main(){ let x = String::new() as String; }
                        ^
error: internal compiler error: translating unsupported cast: collections::string::String (cast_other) -> collections::string::String (cast_other)
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /build/rust/src/rustc-1.1.0/src/libsyntax/diagnostic.rs:230

stack backtrace:
   1:     0x7f9eebf432d9 - sys::backtrace::write::h534114ba1b06b93294r
   2:     0x7f9eebf4b1f9 - panicking::on_panic::h4e97afe0febd2c7biJw
   3:     0x7f9eebf0bff2 - rt::unwind::begin_unwind_inner::hfe7dd1cef83ccc0fsow
   4:     0x7f9ee92f0a2d - rt::unwind::begin_unwind::h11509303451443813476
   5:     0x7f9ee92f10eb - diagnostic::Handler::bug::h238bf6cb3345eafa4aC
   6:     0x7f9ee9ed617b - session::Session::bug::h3b46b49c0728a5bdior
   7:     0x7f9eeaddc476 - trans::expr::trans_imm_cast::h9d654d95d7bc5dc4TCC
   8:     0x7f9eeadced97 - trans::expr::trans_unadjusted::hde606eb9ff3154c3cPA
   9:     0x7f9eeada5ecd - trans::expr::trans_into::hada10aa0abe58f6fXaA
  10:     0x7f9eeae2217a - trans::_match::mk_binding_alloca::h16266239282942992319
  11:     0x7f9eead19fae - trans::base::init_local::hfb9990c4bb499977E0g
  12:     0x7f9eead29db6 - trans::controlflow::trans_block::h58628df23515fb60z3u
  13:     0x7f9eead289f1 - trans::base::trans_closure::h8e149909d93e9d35jHh
  14:     0x7f9eead2a6ca - trans::base::trans_fn::h6fdd3daa5a1290101Rh
  15:     0x7f9eead2d497 - trans::base::trans_item::hae1a16e69a6f2b67dgi
  16:     0x7f9eead3b302 - trans::base::trans_crate::h60d17a2e7a10efe004i
  17:     0x7f9eec4911e6 - driver::phase_4_translate_to_llvm::h2764cf85036c98d7nOa
  18:     0x7f9eec46cfe6 - driver::compile_input::hd8975b759aec0d60Qba
  19:     0x7f9eec5230e1 - run_compiler::h3b0c3beaef2163aa75b
  20:     0x7f9eec520932 - boxed::F.FnBox<A>::call_box::h5202619178778601284
  21:     0x7f9eec51fef9 - rt::unwind::try::try_fn::h4053862560305393821
  22:     0x7f9eebfba3d8 - rust_try_inner
  23:     0x7f9eebfba3c5 - rust_try
  24:     0x7f9eec520194 - boxed::F.FnBox<A>::call_box::h4599430653034051152
  25:     0x7f9eebf49f91 - sys::thread::Thread::new::thread_start::h089e987aa4c0e52dzvv
  26:     0x7f9ee6a9b353 - start_thread
  27:     0x7f9eebb9bbfc - __clone
  28:                0x0 - <unknown>

[mitaa]

This is fixed in beta (dup of #25143)

[alexcrichton]

Thanks @mitaa!