rustdoc crashes when running --merge=finalize without an input crate root #146646
Description
Repro
WHICH_RUSTDOC=rustdoc "$WHICH_RUSTDOC" --version rm -rf repro mkdir repro # make an empty crate (the source code doesn't matter) touch repro/base.rs # get doc.parts for this crate "$WHICH_RUSTDOC" \ --out-dir repro/doc \ -Zunstable-options \ --merge=none \ --parts-out-dir repro/doc.parts/base \ repro/base.rs # try to run --merge=finalize without an input crate "$WHICH_RUSTDOC" \ --out-dir repro/merged \ -Zunstable-options \ --merge=finalize \ --include-parts-dir repro/doc.parts/baseOutput
rustdoc 1.92.0-nightly (a454fccb0 2025-09-15) thread 'main' (503139) panicked at /rust/deps/scoped-tls-1.0.1/src/lib.rs:168:9: cannot access a scoped thread local variable without calling `set` first stack backtrace: 0: 0x7f7af5a4bdf3 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h830fbe15fbab381b 1: 0x7f7af6201b58 - core::fmt::write::hf661a9e75db120a3 2: 0x7f7af5a00d71 - std::io::Write::write_fmt::he76c5adbbdfd1600 3: 0x7f7af5a11d22 - std::sys::backtrace::BacktraceLock::print::hb87325f2dc6d4dfe 4: 0x7f7af5a17c69 - std::panicking::default_hook::{{closure}}::h5e01ba9de3335cc4 5: 0x7f7af5a17793 - std::panicking::default_hook::h47934e1f610fefc5 6: 0x7f7af4a08797 - std[c207121dba9f4102]::panicking::update_hook::<alloc[fbc11b1b12ed36cd]::boxed::Box<rustc_driver_impl[d9438a736 c8997f5]::install_ice_hook::{closure#1}>>::{closure#0} 7: 0x7f7af5a1808f - std::panicking::panic_with_hook::hfee0edaf348ac547 8: 0x7f7af5a1763c - std::panicking::begin_panic::{{closure}}::hfab281f595fe6b8e 9: 0x7f7af5a11e59 - std::sys::backtrace::__rust_end_short_backtrace::h18cba0a351de3087 10: 0x7f7af3117d14 - std::panicking::begin_panic::h3e51ad6bf38ddb4a 11: 0x7f7af63e62fd - <rustc_span[acd9e562735339de]::symbol::Symbol>::intern 12: 0x5607faf93963 - rustdoc[de4b4e234c0ac729]::html::render::write_shared::write_rendered_cross_crate_info 13: 0x5607faf8f90a - rustdoc[de4b4e234c0ac729]::html::render::write_shared::write_not_crate_specific 14: 0x5607fae3f8ad - rustdoc[de4b4e234c0ac729]::main_args 15: 0x5607fae39e34 - rustdoc[de4b4e234c0ac729]::main 16: 0x5607fb09b943 - std[c207121dba9f4102]::sys::backtrace::__rust_begin_short_backtrace::<fn(), ()> 17: 0x5607fb09b959 - std[c207121dba9f4102]::rt::lang_start::<()>::{closure#0} 18: 0x7f7af73fb8a5 - std::rt::lang_start_internal::h78f37f9ccd5c4fa5 19: 0x5607fb09b9a8 - main 20: 0x7f7af0c33ca8 - __libc_start_call_main at ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16 21: 0x7f7af0c33d65 - __libc_start_main_impl at ./csu/../csu/libc-start.c:360:3 22: 0x5607fab45ec4 - <unknown> 23: 0x0 - <unknown> error: 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-rustdoc&template=ice.md note: please make sure that you have updated to the latest nightly note: please attach the file at `/usr/local/google/home/ethanws/rustdoc-investigation/rustc-ice-2025-09-16T16_34_16-503139.txt` to your bu g report note: compiler flags: -Z unstable-options query stack during panic: end of query stack Motivation
Being able to run rustdoc without an input crate root in the --merge=finalize mode is a core workflow described in RFC 3662, "This flag may be used with or without an input crate root, in which case it only links crates included via --include-parts-dir."
The commit 8511e40 seems to have introduced the call to Symbol::intern that appears in the above backtrace.
Calling rustdoc --merge=finalize with a crate root causes no crash
WHICH_RUSTDOC=rustdoc "$WHICH_RUSTDOC" --version rm -rf repro mkdir repro # make an empty crate (the source code doesn't matter) touch repro/base.rs # get doc.parts for this crate "$WHICH_RUSTDOC" \ --out-dir repro/doc \ -Zunstable-options \ --merge=none \ --parts-out-dir repro/doc.parts/base \ repro/base.rs # Add crate root touch repro/input.rs "$WHICH_RUSTDOC" \ --out-dir repro/merged \ -Zunstable-options \ --merge=finalize \ --include-parts-dir repro/doc.parts/base \ repro/input.rs # crate root