assume all sequences have (unique) spans for now

[SOF3]

Steps to reproduce:

• Extract the archive delegate_impl.tar[1].gz

• Run cargo build

• Run cargo test

The following generated macro is a likely source of error:

pub trait Foo {
    fn len(&self) -> usize;
}
macro_rules ! delegate_foo
{
    ($ (< $ ($ types : ty) , * > :) ? $ (< $ ($ trait_types : ty) , * > for) ?
     $ struct : ty : $ inner : ident ; $ ($ extra : tt) *) =>
    {
        impl Foo for $ struct
        { fn len (& self) -> usize { self . $ inner . len () } $ ($ extra) * }
    } ;
}

However, directly putting this macro does not seem to cause a compiler crash: playground link

It appears that the crash only occurs when the macro-by-example generated from a proc-macro.

The full error message:

 # RUST_BACKTRACE=1 cargo test -v
       Fresh unicode-xid v0.1.0
       Fresh strsim v0.7.0
       Fresh fnv v1.0.6
       Fresh ident_case v1.0.1
       Fresh unicode-segmentation v1.3.0
       Fresh heck v0.3.1
       Fresh proc-macro2 v0.4.30
       Fresh quote v0.6.13
       Fresh syn v0.15.39
       Fresh darling_core v0.9.0
       Fresh darling_macro v0.9.0
       Fresh darling v0.9.0
   Compiling delegate-impl v0.1.0 (/home/sofe/tmp/rust-macro-panic/delegate_impl)
     Running `rustc --edition=2018 --crate-name basic tests/basic.rs --color always --emit=dep-info,link -C debuginfo=2 --test -C metadata=4c780bcd93c95670 -C extra-filename=-4c780bcd93c95670 --out-dir /home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps -C incremental=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/incremental -L dependency=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps --extern darling=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libdarling-1cf0f95a99f4d219.rlib --extern delegate_impl=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libdelegate_impl-9e2dd1dcd849a18f.so --extern heck=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libheck-dd3bc44162558753.rlib --extern proc_macro2=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libproc_macro2-1e51e1908d73493d.rlib --extern quote=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libquote-5c27d0a83206aa3b.rlib --extern syn=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libsyn-26e5871ced9ec69a.rlib`
pub trait Foo { fn len (& self) -> usize ; } macro_rules ! delegate_foo
{
    ($ (< $ ($ types : ty) , * > :) ? $ (< $ ($ trait_types : ty) , * > for) ?
     $ struct : ty : $ inner : ident ; $ ($ extra : tt) *) =>
    {
        impl Foo for $ struct
        { fn len (& self) -> usize { self . $ inner . len () } $ ($ extra) * }
    } ;
}
thread 'rustc' panicked at 'assume all sequences have (unique) spans for now', src/libsyntax/ext/tt/macro_rules.rs:694:29
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: rustc::util::common::panic_hook
   7: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:481
   8: std::panicking::begin_panic
   9: syntax::ext::tt::macro_rules::check_matcher_core::{{closure}}
  10: syntax::ext::tt::macro_rules::check_matcher_core
  11: syntax::ext::tt::macro_rules::check_lhs_nt_follows
  12: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  13: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
  14: syntax::ext::tt::macro_rules::compile
  15: rustc_resolve::macros::<impl rustc_resolve::Resolver>::define_macro
  16: syntax::ext::expand::AstFragment::visit_with
  17: rustc_resolve::macros::<impl syntax::ext::base::Resolver for rustc_resolve::Resolver>::visit_ast_fragment_with_placeholders
  18: syntax::ext::expand::MacroExpander::collect_invocations
  19: syntax::ext::expand::MacroExpander::expand_fragment
  20: syntax::ext::expand::MacroExpander::expand_crate
  21: rustc_interface::passes::configure_and_expand_inner::{{closure}}
  22: rustc::util::common::time
  23: rustc_interface::passes::configure_and_expand_inner
  24: rustc_interface::passes::configure_and_expand::{{closure}}
  25: rustc_data_structures::box_region::PinnedGenerator<I,A,R>::new
  26: rustc_interface::passes::configure_and_expand
  27: rustc_interface::queries::Query<T>::compute
  28: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::expansion
  29: rustc_interface::interface::run_compiler_in_existing_thread_pool
  30: std::thread::local::LocalKey<T>::with
  31: syntax::with_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
query stack during panic:
end of query stack

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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.38.0-nightly (e3cebcb3b 2019-07-19) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental

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

error: Could not compile `delegate-impl`.

Caused by:
  process didn't exit successfully: `rustc --edition=2018 --crate-name basic tests/basic.rs --color always --emit=dep-info,link -C debuginfo=2 --test -C metadata=4c780bcd93c95670 -C extra-filename=-4c780bcd93c95670 --out-dir /home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps -C incremental=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/incremental -L dependency=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps --extern darling=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libdarling-1cf0f95a99f4d219.rlib --extern delegate_impl=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libdelegate_impl-9e2dd1dcd849a18f.so --extern heck=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libheck-dd3bc44162558753.rlib --extern proc_macro2=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libproc_macro2-1e51e1908d73493d.rlib --extern quote=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libquote-5c27d0a83206aa3b.rlib --extern syn=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/debug/deps/libsyn-26e5871ced9ec69a.rlib` (exit code: 101)

Using --release gives a similar result:

# RUST_BACKTRACE=1 cargo test --release -v
       Fresh unicode-xid v0.1.0
       Fresh fnv v1.0.6
       Fresh strsim v0.7.0
       Fresh ident_case v1.0.1
       Fresh unicode-segmentation v1.3.0
       Fresh proc-macro2 v0.4.30
       Fresh heck v0.3.1
       Fresh quote v0.6.13
       Fresh syn v0.15.39
       Fresh darling_core v0.9.0
       Fresh darling_macro v0.9.0
       Fresh darling v0.9.0
   Compiling delegate-impl v0.1.0 (/home/sofe/tmp/rust-macro-panic/delegate_impl)
     Running `rustc --edition=2018 --crate-name basic tests/basic.rs --color always --emit=dep-info,link -C opt-level=3 --test -C metadata=9e9bf208733a178a -C extra-filename=-9e9bf208733a178a --out-dir /home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps -L dependency=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps --extern darling=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libdarling-0afbc4e9dd403117.rlib --extern delegate_impl=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libdelegate_impl-af9dd6baa1beb54b.so --extern heck=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libheck-d871e96a3d2eb560.rlib --extern proc_macro2=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libproc_macro2-2ff74a27828d9340.rlib --extern quote=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libquote-c099edfd78a33426.rlib --extern syn=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libsyn-42c6f8f520bc6764.rlib`
pub trait Foo { fn len (& self) -> usize ; } macro_rules ! delegate_foo
{
    ($ (< $ ($ types : ty) , * > :) ? $ (< $ ($ trait_types : ty) , * > for) ?
     $ struct : ty : $ inner : ident ; $ ($ extra : tt) *) =>
    {
        impl Foo for $ struct
        { fn len (& self) -> usize { self . $ inner . len () } $ ($ extra) * }
    } ;
}
thread 'rustc' panicked at 'assume all sequences have (unique) spans for now', src/libsyntax/ext/tt/macro_rules.rs:694:29
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: rustc::util::common::panic_hook
   7: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:481
   8: std::panicking::begin_panic
   9: syntax::ext::tt::macro_rules::check_matcher_core::{{closure}}
  10: syntax::ext::tt::macro_rules::check_matcher_core
  11: syntax::ext::tt::macro_rules::check_lhs_nt_follows
  12: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  13: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
  14: syntax::ext::tt::macro_rules::compile
  15: rustc_resolve::macros::<impl rustc_resolve::Resolver>::define_macro
  16: syntax::ext::expand::AstFragment::visit_with
  17: rustc_resolve::macros::<impl syntax::ext::base::Resolver for rustc_resolve::Resolver>::visit_ast_fragment_with_placeholders
  18: syntax::ext::expand::MacroExpander::collect_invocations
  19: syntax::ext::expand::MacroExpander::expand_fragment
  20: syntax::ext::expand::MacroExpander::expand_crate
  21: rustc_interface::passes::configure_and_expand_inner::{{closure}}
  22: rustc::util::common::time
  23: rustc_interface::passes::configure_and_expand_inner
  24: rustc_interface::passes::configure_and_expand::{{closure}}
  25: rustc_data_structures::box_region::PinnedGenerator<I,A,R>::new
  26: rustc_interface::passes::configure_and_expand
  27: rustc_interface::queries::Query<T>::compute
  28: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::expansion
  29: rustc_interface::interface::run_compiler_in_existing_thread_pool
  30: std::thread::local::LocalKey<T>::with
  31: syntax::with_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
query stack during panic:
end of query stack

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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.38.0-nightly (e3cebcb3b 2019-07-19) running on x86_64-unknown-linux-gnu

note: compiler flags: -C opt-level=3

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

error: Could not compile `delegate-impl`.

Caused by:
  process didn't exit successfully: `rustc --edition=2018 --crate-name basic tests/basic.rs --color always --emit=dep-info,link -C opt-level=3 --test -C metadata=9e9bf208733a178a -C extra-filename=-9e9bf208733a178a --out-dir /home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps -L dependency=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps --extern darling=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libdarling-0afbc4e9dd403117.rlib --extern delegate_impl=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libdelegate_impl-af9dd6baa1beb54b.so --extern heck=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libheck-d871e96a3d2eb560.rlib --extern proc_macro2=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libproc_macro2-2ff74a27828d9340.rlib --extern quote=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libquote-c099edfd78a33426.rlib --extern syn=/home/sofe/tmp/rust-macro-panic/delegate_impl/target/release/deps/libsyn-42c6f8f520bc6764.rlib` (exit code: 101)

You can try removing the first one or two parts in the macro pattern and the error disappears.

[Centril]

cc @petrochenkov

[petrochenkov]

cc @mark-i-m @ia0

[mark-i-m]

The offending code is here:

rust/src/libsyntax/ext/tt/macro_rules.rs

Lines 653 to 655 in 299ef86

	Some(&None) => {
	panic!("assume all sequences have (unique) spans for now");
	}

TBH, I'm not really sure what it is checking, and I don't have time to look into it right now (work is busy)... Sorry about that.

It seems that the proc_macro is somehow generating some tokens or TokenTrees (especially in a Sequence [i.e. a token repetition]) that don't have spans somehow. @petrochenkov is that even possible?

It looks like pnkfelix wrote this code originally 4 years ago. It hasn't been touched in years. @petrochenkov do you know if there have been any changes in proc_macros that could have exposed this behavior?