internal compiler error (rust 1.0.0-beta) with early return

[alserio]

The following code produces an ICE on playpen with rust 1.0.0-beta or nightly:

fn main() -> () {
    let _ = f();
}

fn f() -> usize {
    if true {
        return 1;      
    }                   
    let x = 0;
    x
}  

error: internal compiler error: trans_local_var: no datum for local/arg 26 found
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>', /home/rustbuild/src/rust-buildbot/slave/beta-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:190

playpen: application terminated with error code 101

The code compiles when the if condition is false (or not immediately true), when the last line uses an explicit return or when the value is returned without let expression.

[sfackler]

bactrace:

error: internal compiler error: trans_local_var: no datum for local/arg 26 found
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>', /home/rustbuild/src/rust-buildbot/slave/beta-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:190

stack backtrace:
   1:     0x7f69c383c3c8 - sys::backtrace::write::h179e141147f9ee14IJC
   2:     0x7f69c3867770 - panicking::on_panic::h6aa569d33389f0cfsXI
   3:     0x7f69c379f4a3 - rt::unwind::begin_unwind_inner::h082f07869f4b9731ACI
   4:     0x7f69c0b6504d - rt::unwind::begin_unwind::h13428428822164950735
   5:     0x7f69c0b657a2 - diagnostic::Handler::bug::h7dec5f2940917255ZsB
   6:     0x7f69c157882b - session::Session::bug::hc743ab3e9fbf0b0bnYq
   7:     0x7f69c2eefd78 - trans::expr::trans_local_var::hd7325e6f6b345fc2NMi
   8:     0x7f69c2ee6591 - trans::expr::trans_def::h2fd28f24ac3b6462rli
   9:     0x7f69c2ed2ce5 - trans::expr::trans_unadjusted::hf93051714e2bb83eTXh
  10:     0x7f69c2e88889 - trans::expr::trans_into::h6740c9e159fab14cgfh
  11:     0x7f69c2e898d2 - trans::controlflow::trans_block::hca8dabb22968b279H6d
  12:     0x7f69c2f605bf - trans::base::trans_closure::h2b9d4a88090cb2c4Qtt
  13:     0x7f69c2e72506 - trans::base::trans_fn::h13eecdaa7f8f7dbfzEt
  14:     0x7f69c2e6d19f - trans::base::trans_item::hcd09515ced7a23baP2t
  15:     0x7f69c2f68afc - trans::base::trans_crate::hdffc9e3841dc9fb5lZu
  16:     0x7f69c3ec7bbf - driver::phase_4_translate_to_llvm::hfb4ae79c3a76d704aOa
  17:     0x7f69c3e9f60b - driver::compile_input::h7c62c2870ff901f6Qba
  18:     0x7f69c3f56a25 - run_compiler::hc815b49ce638c28eV4b
  19:     0x7f69c3f5433d - boxed::F.FnBox<A>::call_box::h4290333406520961126
  20:     0x7f69c3f53879 - rt::unwind::try::try_fn::h13999576404798567721
  21:     0x7f69c38e3c68 - rust_try_inner
  22:     0x7f69c38e3c55 - rust_try
  23:     0x7f69c3f53b4b - boxed::F.FnBox<A>::call_box::h14489442628055152240
  24:     0x7f69c3852781 - sys::thread::create::thread_start::h02b7da32b4d7a4aaExH
  25:     0x7f69bd643373 - start_thread
  26:     0x7f69c341227c - __clone
  27:                0x0 - <unknown>

[dotdash]

Same ICE with:

fn main() {
    return ();
    let x = ();
    x
}