ICE when parsing function arguments

[bombless]

Only 8 characters to reproduce it:

fn a(b<)

bombless@bombless-PC ~
$ RUST_BACKTRACE=1 rustc bug.rs
bug.rs:1:6: 1:7 error: internal compiler error: ident only path should have been covered already
bug.rs:1 fn a(b<)
              ^
note: the compiler unexpectedly panicked. 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
thread 'rustc' panicked at 'Box<Any>', D:\msys64rust\home\bombless\rust\src\libsyntax\diagnostic.rs:129

stack backtrace:
   1: 0x62f64830 - rt::unwind::register::h8870fb6c80a96162QRK
   2: 0x62ec370a - rt::unwind::begin_unwind_inner::h782a5368d71edb288OK
   3: 0x6590a5e9 - diagnostic::SpanHandler::span_bug::h153d77da0c8b79b196E
   4: 0x6590a5bf - diagnostic::SpanHandler::span_bug::h153d77da0c8b79b196E
   5: 0x65933028 - parse::parser::Parser<'a>::parse_pat::hfc606892dcf1e2427ML
   6: 0x6592644c - parse::parser::Parser<'a>::parse_arg_general::h87ab09e2c6d4568ev6J
   7: 0x6595531b - parse::classify::stmt_ends_with_semi::h07b852d618f193bfsAV
   8: 0x65925172 - parse::parser::Parser<'a>::parse_unsafety::h5d507ee9f7690141xKJ
   9: 0x659557cb - parse::parser::Parser<'a>::parse_fn_decl::heb8140fc584204f3MEM
  10: 0x65955eda - parse::parser::Parser<'a>::parse_fn_decl::heb8140fc584204f3MEM
  11: 0x6594ae08 - parse::token::Token::is_any_keyword::h7c1a1e386dba65efPTT
  12: 0x6595ce97 - parse::parser::Parser<'a>::parse_single_struct_field::h4ca2f5d7200a3b90dhN
  13: 0x65967886 - parse::parser::Parser<'a>::parse_crate_mod::h09cf5f049598b06epnO
  14: 0x6597a557 - parse::parse_crate_from_file::hb980f2e644d47bf9DOV
  15: 0x6b7ed405 - driver::PhaseController<'a>::basic::h3b7eeffad2d095475ka
  16: 0x6b7c4b55 - driver::phase_1_parse_input::hf383c107d26ed93fOra
  17: 0x6b7c15c9 - driver::compile_input::hc5c82f462e8ae803Eba
  18: 0x6b893a7b - run_compiler::h98d0afe0dbcfcf825bc
  19: 0x6b8913e1 - run::h60d407976fe85de6Ibc
  20: 0x6b890056 - run::h60d407976fe85de6Ibc
  21: 0x62f94fac - rust_try
  22: 0x62f549e4 - sys::tcp::TcpListener::bind::h223a0577de50d7e7N9F
  23: 0x74db919f - BaseThreadInitThunk
  24: 0x76f20bbb - RtlInitializeExceptionChain

$ rustc -V -v
rustc 1.0.0-dev (b6d91a2bd 2015-02-15 07:53:07 +0000)
binary: rustc
commit-hash: b6d91a2bdac45cd919497a24207fab843124d4ba
commit-date: 2015-02-15 07:53:07 +0000
host: i686-pc-windows-gnu
release: 1.0.0-dev

[bombless]

This bug is actually the same as #22426