ICE: -Zunpretty=hir "AST generic args printed by HIR pretty-printer"

[matthiaskrgr]

./src/test/ui/issues/issue-43424.rs

Code

#![allow(unused)]

macro_rules! m {
    ($attr_path: path) => {
        #[$attr_path]
        fn f() {}
    }
}

m!(inline<u8>); //~ ERROR: unexpected generic arguments in path

fn main() {}

Meta

rustc --version --verbose:

rustc 1.62.0-nightly (6dd68402c 2022-05-11)
binary: rustc
commit-hash: 6dd68402c5d7da168f87d8551dd9aed1d8a21893
commit-date: 2022-05-11
host: x86_64-unknown-linux-gnu
release: 1.62.0-nightly
LLVM version: 14.0.1

Error output

rustc -Zunpretty=hir ./src/test/ui/issues/issue-43424.rs

error: unexpected generic arguments in path
  --> ./src/test/ui/issues/issue-43424.rs:10:10
   |
10 | m!(inline<u8>); //~ ERROR: unexpected generic arguments in path
   |          ^^^^

thread 'rustc' panicked at 'AST generic args printed by HIR pretty-printer', compiler/rustc_hir_pretty/src/lib.rs:136:9

Backtrace

thread 'rustc' panicked at 'AST generic args printed by HIR pretty-printer', compiler/rustc_hir_pretty/src/lib.rs:136:9
stack backtrace:
   0:     0x7ffa9029de5d - std::backtrace_rs::backtrace::libunwind::trace::h7a9c384780f2ae7b
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7ffa9029de5d - std::backtrace_rs::backtrace::trace_unsynchronized::heb75d166ca8b8236
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7ffa9029de5d - std::sys_common::backtrace::_print_fmt::h322cd7edf00cb3b5
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7ffa9029de5d - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h2bdd168863171e89
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7ffa902f9adc - core::fmt::write::he97f80a3d639b1e1
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/core/src/fmt/mod.rs:1196:17
   5:     0x7ffa9028f5e1 - std::io::Write::write_fmt::hfad334cf5c2887e6
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/io/mod.rs:1654:15
   6:     0x7ffa902a0b75 - std::sys_common::backtrace::_print::hb3fd4d16502c8b4b
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7ffa902a0b75 - std::sys_common::backtrace::print::h20c8699087b98c21
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7ffa902a0b75 - std::panicking::default_hook::{{closure}}::hceced8f030c627d7
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/panicking.rs:295:22
   9:     0x7ffa902a07e9 - std::panicking::default_hook::hf622cc58f7fb1da8
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/panicking.rs:314:9
  10:     0x7ffa90ae84a1 - rustc_driver[8eec3efc1f3aef49]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7ffa902a1346 - std::panicking::rust_panic_with_hook::h6a32c5574ceba44d
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/panicking.rs:702:17
  12:     0x7ffa902a1109 - std::panicking::begin_panic_handler::{{closure}}::h33a7eb85cc49019a
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/panicking.rs:586:13
  13:     0x7ffa9029e314 - std::sys_common::backtrace::__rust_end_short_backtrace::hbc4249165d4ceafc
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/sys_common/backtrace.rs:138:18
  14:     0x7ffa902a0e79 - rust_begin_unwind
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/panicking.rs:584:5
  15:     0x7ffa90266133 - core::panicking::panic_fmt::hea2f72507c137b32
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/core/src/panicking.rs:142:14
  16:     0x7ffa917e5192 - <rustc_hir_pretty[64c9283308801d1b]::State as rustc_ast_pretty[bbe234e6f3ca4345]::pprust::state::PrintState>::print_path
  17:     0x7ffa926ef052 - <rustc_hir_pretty[64c9283308801d1b]::State as rustc_ast_pretty[bbe234e6f3ca4345]::pprust::state::PrintState>::print_either_attributes
  18:     0x7ffa9320dc06 - <rustc_hir_pretty[64c9283308801d1b]::State>::print_item
  19:     0x7ffa90aeccd4 - <rustc_driver[8eec3efc1f3aef49]::pretty::NoAnn as rustc_hir_pretty[64c9283308801d1b]::PpAnn>::nested
  20:     0x7ffa917e65bd - <rustc_hir_pretty[64c9283308801d1b]::State>::print_mod
  21:     0x7ffa917e5cfe - rustc_hir_pretty[64c9283308801d1b]::print_crate
  22:     0x7ffa90aeef83 - rustc_driver[8eec3efc1f3aef49]::pretty::print_after_hir_lowering::{closure#1}
  23:     0x7ffa90aeec15 - rustc_driver[8eec3efc1f3aef49]::pretty::print_after_hir_lowering
  24:     0x7ffa90acdca0 - <rustc_interface[d03aac2056e219e8]::passes::QueryContext>::enter::<rustc_driver[8eec3efc1f3aef49]::run_compiler::{closure#1}::{closure#2}::{closure#1}, core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>>
  25:     0x7ffa92b58dc0 - <rustc_interface[d03aac2056e219e8]::interface::Compiler>::enter::<rustc_driver[8eec3efc1f3aef49]::run_compiler::{closure#1}::{closure#2}, core[c5a39be06b715266]::result::Result<core[c5a39be06b715266]::option::Option<rustc_interface[d03aac2056e219e8]::queries::Linker>, rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>>
  26:     0x7ffa92b80e1f - rustc_span[5dae44024ba07c23]::with_source_map::<core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>, rustc_interface[d03aac2056e219e8]::interface::create_compiler_and_run<core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>, rustc_driver[8eec3efc1f3aef49]::run_compiler::{closure#1}>::{closure#1}>
  27:     0x7ffa92b6c9a4 - rustc_interface[d03aac2056e219e8]::interface::create_compiler_and_run::<core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>, rustc_driver[8eec3efc1f3aef49]::run_compiler::{closure#1}>
  28:     0x7ffa92b56f82 - <scoped_tls[9a81942410e5ea2f]::ScopedKey<rustc_span[5dae44024ba07c23]::SessionGlobals>>::set::<rustc_interface[d03aac2056e219e8]::interface::run_compiler<core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>, rustc_driver[8eec3efc1f3aef49]::run_compiler::{closure#1}>::{closure#0}, core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>>
  29:     0x7ffa92b6e09f - std[87b888c30fb8b53d]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[d03aac2056e219e8]::util::run_in_thread_pool_with_globals<rustc_interface[d03aac2056e219e8]::interface::run_compiler<core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>, rustc_driver[8eec3efc1f3aef49]::run_compiler::{closure#1}>::{closure#0}, core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>>::{closure#0}, core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>>
  30:     0x7ffa92b6e1d9 - <<std[87b888c30fb8b53d]::thread::Builder>::spawn_unchecked_<rustc_interface[d03aac2056e219e8]::util::run_in_thread_pool_with_globals<rustc_interface[d03aac2056e219e8]::interface::run_compiler<core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>, rustc_driver[8eec3efc1f3aef49]::run_compiler::{closure#1}>::{closure#0}, core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>>::{closure#0}, core[c5a39be06b715266]::result::Result<(), rustc_errors[ddf493a40e6cbb28]::ErrorGuaranteed>>::{closure#1} as core[c5a39be06b715266]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  31:     0x7ffa902ab253 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h23107667314c5666
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/alloc/src/boxed.rs:1872:9
  32:     0x7ffa902ab253 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h8a72a46bb071903a
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/alloc/src/boxed.rs:1872:9
  33:     0x7ffa902ab253 - std::sys::unix::thread::Thread::new::thread_start::h81657d69ed68fad8
                               at /rustc/6dd68402c5d7da168f87d8551dd9aed1d8a21893/library/std/src/sys/unix/thread.rs:108:17
  34:     0x7ffa900835c2 - start_thread
  35:     0x7ffa90108584 - __clone
  36:                0x0 - <unknown>

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.62.0-nightly (6dd68402c 2022-05-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z unpretty=hir

query stack during panic:
end of query stack
error: aborting due to previous error

[3tilley]

I've had a look at this with amateur eyes, and it appears to be to do with how badly formed macros are treated by the HIR pretty printer. This can be seen by expanding the macro and feeding it through the same command.

Macro

#![allow(unused)]

macro_rules! m {
    ($attr_path: path) => {
        #[$attr_path]
        fn f() {}
    }
}

m!(inline<u8>); //~ ERROR: unexpected generic arguments in path

fn main() {}

Note that also -Z unpretty=hir-tree does not panic on the code above, so it doesn't appear to be a problem that the HIR represents an illegal macro.

Expanded

The result here is more predictable:

#![feature(prelude_import)]
#![allow(unused)]
#[prelude_import]
use std::prelude::rust_2021::*;
#[macro_use]
extern crate std;

macro_rules! m { ($attr_path : path) => { #[$attr_path] fn f() {} } ; }
#[

inline<u8>]
fn f() {}
//~ ERROR: unexpected generic arguments in path

fn main() {}

error: expected one of `(`, `::`, `=`, `[`, `]`, or `{`, found `<`
  --> src\main.rs:11:7
   |
11 | inline<u8>]
   |       ^ expected one of `(`, `::`, `=`, `[`, `]`, or `{`

error: could not compile `expanded` (bin "expanded") due to previous error

Solution

Should the pretty printer learn how to print generic args, even if it's illegal? The code is called here. I don't really understand the purpose of the panic and why generic args are unexpected which makes me nervous to alter the code.

Are there any other valid / invalid macros that anyone can think of to trigger other cases?