ICE: pub extern fn with parameter type &str inside struct impl

[ryantaylor]

struct Test;

impl Test {
    pub extern fn test(val: &str) {

    }
}

When you attempt to compile you get:

thread 'rustc' panicked at 'assertion failed: index < LLVMCountParams(llfn)', ../src/librustc_llvm/lib.rs:2281

stack backtrace:
   1:     0x7f594732b6e9 - sys::backtrace::tracing::imp::write::hc20cecbe7cbc162bPnt
   2:     0x7f5947328c36 - panicking::on_panic::h838652421a384701enx
   3:     0x7f59472f3f9e - sys_common::unwind::begin_unwind_inner::h1941327c7a60c738ffs
   4:     0x7f5942add8bf - sys_common::unwind::begin_unwind::h10325064115155345230
   5:     0x7f5942ade6c8 - get_param::h41f15541bf012b4aDUc
   6:     0x7f594682b985 - trans::base::trans_closure::h9db23c69943cc6edvQi
   7:     0x7f594682ea4f - trans::base::trans_fn::he234bd1782c765fai0i
   8:     0x7f59468330ab - trans::base::trans_item::hdd4c4224f51d93be9qj
   9:     0x7f594683f989 - trans::base::trans_crate::hbcfdc768138ad4feRck
  10:     0x7f59478574dc - driver::phase_4_translate_to_llvm::h281d81b2d864b5a0lPa
  11:     0x7f5947851ba3 - driver::phase_3_run_analysis_passes::closure.21540
  12:     0x7f594782f27c - middle::ty::context::ctxt<'tcx>::create_and_enter::h14146594457946518047
  13:     0x7f594782aa31 - driver::phase_3_run_analysis_passes::h3931958423828830349
  14:     0x7f594780aded - driver::compile_input::h4f0a6e7bed616ea50ba
  15:     0x7f5947970d0b - run_compiler::ha3f4465c73f94406qqc
  16:     0x7f594796e576 - boxed::F.FnBox<A>::call_box::h9054381916092353385
  17:     0x7f594796de84 - sys_common::unwind::try::try_fn::h18243607356614407688
  18:     0x7f5947328538 - __rust_try
  19:     0x7f594731ccd2 - sys_common::unwind::try::inner_try::h074d3cf1bfeda6e7Dbs
  20:     0x7f594796e01e - boxed::F.FnBox<A>::call_box::h2812587830519910695
  21:     0x7f5947330a03 - sys::thread::Thread::new::thread_start::h745044ae17db5a99dGw
  22:     0x7f59412c64a3 - start_thread
  23:     0x7f5946fb813c - clone
  24:                0x0 - <unknown>

Also tested with the following:

use std::path::Path;

struct Test;

impl Test {
    pub extern fn test(val: &Path) {

    }
}

You get:

thread 'rustc' panicked at 'assertion failed: index < LLVMCountParams(llfn)', ../src/librustc_llvm/lib.rs:2281

stack backtrace:
   1:     0x7fab8a7b06e9 - sys::backtrace::tracing::imp::write::hc20cecbe7cbc162bPnt
   2:     0x7fab8a7adc36 - panicking::on_panic::h838652421a384701enx
   3:     0x7fab8a778f9e - sys_common::unwind::begin_unwind_inner::h1941327c7a60c738ffs
   4:     0x7fab85f628bf - sys_common::unwind::begin_unwind::h10325064115155345230
   5:     0x7fab85f636c8 - get_param::h41f15541bf012b4aDUc
   6:     0x7fab89cb0985 - trans::base::trans_closure::h9db23c69943cc6edvQi
   7:     0x7fab89cb3a4f - trans::base::trans_fn::he234bd1782c765fai0i
   8:     0x7fab89cb80ab - trans::base::trans_item::hdd4c4224f51d93be9qj
   9:     0x7fab89cc4989 - trans::base::trans_crate::hbcfdc768138ad4feRck
  10:     0x7fab8acdc4dc - driver::phase_4_translate_to_llvm::h281d81b2d864b5a0lPa
  11:     0x7fab8acd6ba3 - driver::phase_3_run_analysis_passes::closure.21540
  12:     0x7fab8acb427c - middle::ty::context::ctxt<'tcx>::create_and_enter::h14146594457946518047
  13:     0x7fab8acafa31 - driver::phase_3_run_analysis_passes::h3931958423828830349
  14:     0x7fab8ac8fded - driver::compile_input::h4f0a6e7bed616ea50ba
  15:     0x7fab8adf5d0b - run_compiler::ha3f4465c73f94406qqc
  16:     0x7fab8adf3576 - boxed::F.FnBox<A>::call_box::h9054381916092353385
  17:     0x7fab8adf2e84 - sys_common::unwind::try::try_fn::h18243607356614407688
  18:     0x7fab8a7ad538 - __rust_try
  19:     0x7fab8a7a1cd2 - sys_common::unwind::try::inner_try::h074d3cf1bfeda6e7Dbs
  20:     0x7fab8adf301e - boxed::F.FnBox<A>::call_box::h2812587830519910695
  21:     0x7fab8a7b5a03 - sys::thread::Thread::new::thread_start::h745044ae17db5a99dGw
  22:     0x7fab8474b4a3 - start_thread
  23:     0x7fab8a43d13c - clone
  24:                0x0 - <unknown>

However, the following works:

struct Test;

impl Test {
    pub extern fn test(val: &u8) {

    }
}

Rust version:

rustc 1.4.0-beta.1 (d2e13e822 2015-09-15)

Also tested on 1.3.0 stable. Haven't tested on nightly.

[dotdash]

Probably the same problem as #28502

[mrhota]

@steveklabnik this doesn't ICE any more. Tested on play: https://is.gd/3LyZdJ