ICE in elided lifetimes suggestion: `!suggestion.is_empty()`

[dtolnay]

# Cargo.toml

[package]
name = "repro"
version = "0.0.0"
edition = "2018"
publish = false

[lib]
proc-macro = true

// src/main.rs

#![deny(elided_lifetimes_in_paths)]

#[repro::repro]
fn f() -> Ptr<Thing>;

fn main() {}

// src/lib.rs

use proc_macro::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
use std::iter::FromIterator;

#[proc_macro_attribute]
pub fn repro(_args: TokenStream, input: TokenStream) -> TokenStream {
    let call_site = Span::call_site();
    let span = input.into_iter().nth(8).unwrap().span();

    //fn f(_: &::std::fmt::Formatter) {}
    TokenStream::from_iter([
        TokenTree::Ident(Ident::new("fn", call_site)),
        TokenTree::Ident(Ident::new("f", call_site)),
        TokenTree::Group(Group::new(
            Delimiter::Parenthesis,
            TokenStream::from_iter([
                TokenTree::Ident(Ident::new("_", call_site)),
                TokenTree::Punct(punct(':', Spacing::Alone, call_site)),
                TokenTree::Punct(punct('&', Spacing::Alone, call_site)),
                TokenTree::Punct(punct(':', Spacing::Joint, span)),
                TokenTree::Punct(punct(':', Spacing::Alone, span)),
                TokenTree::Ident(Ident::new("std", span)),
                TokenTree::Punct(punct(':', Spacing::Joint, span)),
                TokenTree::Punct(punct(':', Spacing::Alone, span)),
                TokenTree::Ident(Ident::new("fmt", span)),
                TokenTree::Punct(punct(':', Spacing::Joint, span)),
                TokenTree::Punct(punct(':', Spacing::Alone, span)),
                TokenTree::Ident(Ident::new("Formatter", span)),
            ]),
        )),
        TokenTree::Group(Group::new(Delimiter::Brace, TokenStream::new())),
    ])
}

fn punct(ch: char, spacing: Spacing, span: Span) -> Punct {
    let mut punct = Punct::new(ch, spacing);
    punct.set_span(span);
    punct
}

cargo +nightly-2021-12-02 check (this is what I would expect)

error: hidden lifetime parameters in types are deprecated
 --> src/main.rs:4:20
  |
4 | fn f() -> Ptr<Thing>;
  |                    ^- help: indicate the anonymous lifetime: `<'_>`
  |
note: the lint level is defined here
 --> src/main.rs:1:9
  |
1 | #![deny(elided_lifetimes_in_paths)]
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^

error: could not compile `repro` due to previous error

cargo +nightly-2021-12-03 check

thread 'rustc' panicked at 'assertion failed: !suggestion.is_empty()', compiler/rustc_errors/src/diagnostic.rs:342:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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 1.59.0-nightly (acbe4443c 2021-12-02) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [resolve_lifetimes] resolving lifetimes
#1 [named_region_map] looking up a named region
end of query stack
error: could not compile `repro`

Backtrace

stack backtrace:
   0: rust_begin_unwind
             at /rustc/acbe4443cc4c9695c0b74a7b64b60333c990a400/library/std/src/panicking.rs:498:5
   1: core::panicking::panic_fmt
             at /rustc/acbe4443cc4c9695c0b74a7b64b60333c990a400/library/core/src/panicking.rs:107:14
   2: core::panicking::panic
             at /rustc/acbe4443cc4c9695c0b74a7b64b60333c990a400/library/core/src/panicking.rs:48:5
   3: <rustc_errors::diagnostic::Diagnostic>::multipart_suggestion_with_style
   4: <rustc_errors::diagnostic_builder::DiagnosticBuilder>::multipart_suggestion_verbose
   5: <rustc_resolve::late::lifetimes::LifetimeContext>::add_missing_lifetime_specifiers_label
   6: <<rustc_resolve::late::lifetimes::LifetimeContext>::report_elided_lifetime_in_ty::{closure#3} as core::ops::function::FnOnce<(rustc_middle::lint::LintDiagnosticBuilder,)>>::call_once::{shim:vtable#0}
   7: rustc_middle::lint::struct_lint_level::struct_lint_level_impl
   8: <rustc_middle::ty::context::TyCtxt>::struct_span_lint_hir::<alloc::vec::Vec<rustc_span::span_encoding::Span>, <rustc_resolve::late::lifetimes::LifetimeContext>::report_elided_lifetime_in_ty::{closure#3}>
   9: <rustc_resolve::late::lifetimes::LifetimeContext>::resolve_elided_lifetimes
  10: <rustc_resolve::late::lifetimes::LifetimeContext as rustc_hir::intravisit::Visitor>::visit_path
  11: <rustc_resolve::late::lifetimes::LifetimeContext as rustc_hir::intravisit::Visitor>::visit_ty
  12: <rustc_resolve::late::lifetimes::LifetimeContext>::visit_fn_like_elision
  13: <rustc_resolve::late::lifetimes::LifetimeContext as rustc_hir::intravisit::Visitor>::visit_fn
  14: rustc_hir::intravisit::walk_item::<rustc_resolve::late::lifetimes::LifetimeContext>
  15: <rustc_resolve::late::lifetimes::LifetimeContext as rustc_hir::intravisit::Visitor>::visit_item
  16: rustc_resolve::late::lifetimes::resolve_lifetimes
  17: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId, rustc_middle::middle::resolve_lifetime::ResolveLifetimes>
  18: rustc_data_structures::stack::ensure_sufficient_stack::<(rustc_middle::middle::resolve_lifetime::ResolveLifetimes, rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, rustc_span::def_id::LocalDefId, rustc_middle::middle::resolve_lifetime::ResolveLifetimes>::{closure#3}>
  19: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::ArenaCache<rustc_span::def_id::LocalDefId, rustc_middle::middle::resolve_lifetime::ResolveLifetimes>>
  20: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::resolve_lifetimes
  21: rustc_resolve::late::lifetimes::resolve_lifetimes_for
  22: <rustc_resolve::late::lifetimes::provide::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)>>::call_once
  23: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId, core::option::Option<&std::collections::hash::map::HashMap<rustc_hir::hir_id::ItemLocalId, rustc_middle::middle::resolve_lifetime::Region, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>>
  24: rustc_data_structures::stack::ensure_sufficient_stack::<(core::option::Option<&std::collections::hash::map::HashMap<rustc_hir::hir_id::ItemLocalId, rustc_middle::middle::resolve_lifetime::Region, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>, rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, rustc_span::def_id::LocalDefId, core::option::Option<&std::collections::hash::map::HashMap<rustc_hir::hir_id::ItemLocalId, rustc_middle::middle::resolve_lifetime::Region, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>>::{closure#3}>
  25: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalDefId, core::option::Option<&std::collections::hash::map::HashMap<rustc_hir::hir_id::ItemLocalId, rustc_middle::middle::resolve_lifetime::Region, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>>>
  26: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::named_region_map
  27: <rustc_middle::ty::context::TyCtxt>::named_region
  28: rustc_hir::intravisit::walk_ty::<rustc_typeck::collect::has_late_bound_regions::LateBoundRegionsDetector>
  29: rustc_hir::intravisit::walk_fn_decl::<rustc_typeck::collect::has_late_bound_regions::LateBoundRegionsDetector>
  30: rustc_typeck::collect::generics_of
  31: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId, rustc_middle::ty::generics::Generics>
  32: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::generics_of
  33: <rustc_typeck::collect::CollectItemTypesVisitor as rustc_hir::intravisit::Visitor>::visit_item
  34: <rustc_middle::hir::map::Map>::visit_item_likes_in_module::<rustc_hir::intravisit::DeepVisitor<rustc_typeck::collect::CollectItemTypesVisitor>>
  35: rustc_typeck::collect::collect_mod_item_types
  36: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId, ()>
  37: rustc_data_structures::stack::ensure_sufficient_stack::<((), rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, rustc_span::def_id::LocalDefId, ()>::{closure#3}>
  38: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalDefId, ()>>
  39: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::collect_mod_item_types, rustc_query_impl::plumbing::QueryCtxt>
  40: <rustc_middle::hir::map::Map>::for_each_module::<rustc_typeck::check_crate::{closure#0}::{closure#0}::{closure#0}>
  41: <rustc_session::session::Session>::track_errors::<rustc_typeck::check_crate::{closure#0}, ()>
  42: rustc_typeck::check_crate
  43: rustc_interface::passes::analysis
  44: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (), core::result::Result<(), rustc_errors::ErrorReported>>
  45: rustc_data_structures::stack::ensure_sufficient_stack::<(core::result::Result<(), rustc_errors::ErrorReported>, rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, (), core::result::Result<(), rustc_errors::ErrorReported>>::{closure#3}>
  46: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(), core::result::Result<(), rustc_errors::ErrorReported>>>
  47: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt>
  48: <rustc_interface::passes::QueryContext>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}::{closure#3}, core::result::Result<(), rustc_errors::ErrorReported>>
  49: <rustc_interface::interface::Compiler>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_errors::ErrorReported>>
  50: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorReported>, rustc_interface::interface::create_compiler_and_run<core::result::Result<(), rustc_errors::ErrorReported>, rustc_driver::run_compiler::{closure#1}>::{closure#1}>
  51: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorReported>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorReported>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorReported>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 1.59.0-nightly (acbe4443c 2021-12-02) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [resolve_lifetimes] resolving lifetimes
#1 [named_region_map] looking up a named region
#2 [generics_of] computing generics of `f`
#3 [collect_mod_item_types] collecting item types in top-level module
#4 [analysis] running analysis passes on this crate
end of query stack

[dtolnay]

This bisects to #90446 — @cjgillot @jackh726

---

regressed nightly: nightly-2021-12-03
searched commit range: 48a5999...acbe444
regressed commit: 76938d6

bisected with cargo-bisect-rustc v0.6.0

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc 2021-11-08 --end 2021-12-10 --regress ice -- check 

[matthiaskrgr]

There was an issue with similar ICE that has been fixed recently #91461
Does this problem still repro with latest nightly rustc 1.59.0-nightly (0b42deacc 2021-12-09) ?

[dtolnay]

Yes this one still reproduces as of that nightly, which contains #91634.

[apiraino]

Assigning priority as discussed in the Zulip thread of the Prioritization Working Group.

@rustbot label -I-prioritize +P-medium