ICE: not a tail expression

[matthiaskrgr]

auto-reduced (treereduce-rust):

macro_rules! the_macro {
    ( $foo:stmt ; $bar:stmt ; ) => {
        #[cfg()]
        $foo

        #[cfg(bar)]
        $bar
    };
}

fn the_function() {
    the_macro!( (); (); );
}

original:

macro_rules! the_macro {
    ( $foo:stmt ; $bar:stmt ; ) => {
        #[cfg(incomplete_features)]
        $foo
        
        #[cfg(bar)]
        $bar
    };
}

fn the_function() {
    the_macro!( (); (); );
}

Version information

rustc 1.78.0-nightly (b79db437d 2024-02-26)
binary: rustc
commit-hash: b79db437dccd496948bb1819d36ed51598563a98
commit-date: 2024-02-26
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 18.1.0

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --crate-type=lib

Program output

warning: function `the_function` is never used
  --> /tmp/icemaker_global_tempdir.fJLXUZMXByi7/rustc_testrunner_tmpdir_reporting.upzqZTcLzog2/mvce.rs:11:4
   |
11 | fn the_function() {
   |    ^^^^^^^^^^^^
   |
   = note: `#[warn(dead_code)]` on by default

warning: 1 warning emitted

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error: not a tail expression
  --> /tmp/icemaker_global_tempdir.fJLXUZMXByi7/rustc_testrunner_tmpdir_reporting.upzqZTcLzog2/mvce.rs:12:17
   |
12 |     the_macro!( (); (); );
   |                 ^^
   |
note: delayed at compiler/rustc_parse/src/parser/diagnostics.rs:818:43
         0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
         1: <rustc_errors::DiagCtxt>::emit_diagnostic
         2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
         3: <rustc_parse::parser::Parser>::attr_on_non_tail_expr
         4: <rustc_parse::parser::Parser>::parse_full_stmt
         5: <rustc_expand::mbe::macro_rules::ParserAnyMacro>::make
         6: <rustc_expand::expand::MacroExpander>::fully_expand_fragment
         7: <rustc_expand::expand::MacroExpander>::expand_crate
         8: rustc_interface::passes::resolver_for_lowering
         9: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::resolver_for_lowering::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        10: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        11: rustc_query_impl::query_impl::resolver_for_lowering::get_query_non_incr::__rust_end_short_backtrace
        12: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}
        13: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
        14: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        15: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                   at /rustc/b79db437dccd496948bb1819d36ed51598563a98/library/alloc/src/boxed.rs:2016:9
        16: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                   at /rustc/b79db437dccd496948bb1819d36ed51598563a98/library/alloc/src/boxed.rs:2016:9
        17: std::sys::pal::unix::thread::Thread::new::thread_start
                   at /rustc/b79db437dccd496948bb1819d36ed51598563a98/library/std/src/sys/pal/unix/thread.rs:108:17
        18: <unknown>
        19: <unknown>
  --> /tmp/icemaker_global_tempdir.fJLXUZMXByi7/rustc_testrunner_tmpdir_reporting.upzqZTcLzog2/mvce.rs:12:17
   |
12 |     the_macro!( (); (); );
   |                 ^^

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 1.78.0-nightly (b79db437d 2024-02-26) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -Z dump-mir-dir=dir

query stack during panic:
end of query stack

[matthiaskrgr]

It seems the not a tail expression pops up since #120586 cc @ShE3py

The code starts ICEing in general since #117988 cc @estebank

[ShE3py]

@rustbot claim