compiler panic on "let v[0] = v[1]" where v is a vector

[mikeantonacci]

I was playing with rust for the first time today and I tried this code:

fn main(){
    let mut v = vec![5, 6, 5, 4, 3, 2];
    let tmp = v[0];
    let v[0] = v[1];
    let v[1] = tmp;
}

In retrospect that shouldn't compile anyway, but when I tried instead of it just being an error the compiler panics. ## Meta

rustc --version --verbose:
rustc 1.0.0-nightly (270a677d4 2015-03-07) (built 2015-03-07)
binary: rustc
commit-hash: 270a677d4d698916f5ad103f0afc3c070b8dbeb4
commit-date: 2015-03-07
build-date: 2015-03-07
host: x86_64-unknown-linux-gnu
release: 1.0.0-nightly

Backtrace:
thread 'rustc' panicked at 'Box', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:129

stack backtrace:
1: 0x7ffd2bf5d2d2 - sys::backtrace::write::he3277a63d69f5b66QBA
2: 0x7ffd2bf83322 - panicking::on_panic::h2a4421d00c8eaa07jHJ
3: 0x7ffd2bec9a69 - rt::unwind::begin_unwind_inner::hb49f4d2d01640667mnJ
4: 0x7ffd294fd4ad - rt::unwind::begin_unwind::h7009344801856954356
5: 0x7ffd294fd453 - diagnostic::SpanHandler::span_bug::hc2a2d6179f91087747D
6: 0x7ffd29523445 - parse::parser::Parser<'a>::parse_pat::h7bb056c6956d3cabfHK
7: 0x7ffd2953541d - parse::parser::Parser<'a>::parse_local::hf9e9abc5dbe40b54zYK
8: 0x7ffd2953671f - parse::parser::Parser<'a>::parse_stmt::hf64ef6e19a06ac72k1K
9: 0x7ffd2953f389 - parse::parser::Parser<'a>::parse_block_tail_::h4c891b4206c9ae93tcL
10: 0x7ffd2951d9bc - parse::parser::Parser<'a>::parse_inner_attrs_and_block::h16f9671c2a8402a7VaL
11: 0x7ffd29543965 - parse::parser::Parser<'a>::parse_item_fn::h22fd08f202ca7c8dkQL
12: 0x7ffd29539c78 - parse::parser::Parser<'a>::parse_item_::h6fa6dafc5db24c9fUOM
13: 0x7ffd29549e95 - parse::parser::Parser<'a>::parse_mod_items::hc345aee461327f21UeM
14: 0x7ffd29551f1c - parse::parser::Parser<'a>::parse_crate_mod::hb0b177721e0e02a2rfN
15: 0x7ffd295638b8 - parse::parse_crate_from_file::h9da771b7e7d3ce72ftU
16: 0x7ffd2c584bd8 - driver::phase_1_parse_input::closure.15543
17: 0x7ffd2c55fd87 - driver::phase_1_parse_input::h22478ea7b47ad567Kqa
18: 0x7ffd2c55c560 - driver::compile_input::h4ead3acd85265c84Nba
19: 0x7ffd2c621ebd - run_compiler::h297fa686def10927G6b
20: 0x7ffd2c61fc2c - thunk::F.Invoke<A, R>::invoke::h13212375243324058858
21: 0x7ffd2c61e880 - rt::unwind::try::try_fn::h15556897595580953244
22: 0x7ffd2bfef0f8 - rust_try_inner
23: 0x7ffd2bfef0e5 - rust_try
24: 0x7ffd2c61f00b - thunk::F.Invoke<A, R>::invoke::h6333748217615269386
25: 0x7ffd2bf70b25 - sys::thread::thread_start::h14dbe992a2cfcf49t8E
26: 0x7ffd25fe2373 - start_thread
27: 0x7ffd2bb5227c - __clone
28: 0x0 -

[petrochenkov]

Fixed by #23930

[petrochenkov]

And tested as well.
https://github.com/rust-lang/rust/blob/master/src/test/parse-fail/pat-lt-bracket-5.rs

[alexcrichton]

Thanks!