Incompatibility with extern_absolute_paths feature

[sinkuu]

Panic occurs inside rls-analysis when extern_absolute_paths feature is used.

// main.rs
#![feature(extern_absolute_paths)]

use serde::Serialize;

fn main() {
    println!("Hello, world!");
}

# Cargo.toml
[dependencies]
serde = "*"

thread '<unnamed>' panicked at 'index out of bounds: the len is 11 but the index is 11', /checkout/src/libcore/slice/mod.rs:865:10
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:71
             at libstd/sys_common/backtrace.rs:59
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:207
   3: std::panicking::default_hook
             at libstd/panicking.rs:223
   4: core::ops::function::Fn::call
   5: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:403
   6: std::panicking::begin_panic_fmt
             at libstd/panicking.rs:349
   7: rust_begin_unwind
             at libstd/panicking.rs:325
   8: core::panicking::panic_fmt
             at libcore/panicking.rs:72
   9: core::panicking::panic_bounds_check
             at libcore/panicking.rs:58
  10: rls_analysis::lowering::CrateReader::id_from_compiler_id
  11: rls_analysis::lowering::CrateReader::read_crate
  12: rls_analysis::lowering::lower
  13: <rls_analysis::AnalysisHost<L>>::reload_from_analysis
  14: rls::actions::post_build::AnalysisQueue::run_worker_thread
  15: __rust_maybe_catch_panic
             at libpanic_unwind/lib.rs:102
  16: <F as alloc::boxed::FnBox<A>>::call_box
  17: std::sys_common::thread::start_thread
             at /checkout/src/liballoc/boxed.rs:793
             at libstd/sys_common/thread.rs:24
  18: std::sys::unix::thread::Thread::new::thread_start
             at libstd/sys/unix/thread.rs:90
  19: start_thread
  20: __clone

[nrc]

This is tracked in #729 (although the error message is different, the cause is the same). Solution is currently blocked on a rustc patch.