From 76197921079737fdd499e12016ac056674b5119f Mon Sep 17 00:00:00 2001 From: Nicholas Nethercote Date: Fri, 9 Feb 2024 06:42:50 +1100 Subject: Fix `ErrorGuaranteed` unsoundness with stash/steal. When you stash an error, the error count is incremented. You can then use the non-zero error count to get an `ErrorGuaranteed`. You can then steal the error, which decrements the error count. You can then cancel the error. Example code: ``` fn unsound(dcx: &DiagCtxt) -> ErrorGuaranteed { let sp = rustc_span::DUMMY_SP; let k = rustc_errors::StashKey::Cycle; dcx.struct_err("bogus").stash(sp, k); // increment error count on stash let guar = dcx.has_errors().unwrap(); // ErrorGuaranteed from error count > 0 let err = dcx.steal_diagnostic(sp, k).unwrap(); // decrement error count on steal err.cancel(); // cancel error guar // ErrorGuaranteed with no error emitted! } ``` This commit fixes the problem in the simplest way: by not counting stashed errors in `DiagCtxt::{err_count,has_errors}`. However, just doing this without any other changes leads to over 40 ui test failures. Mostly because of uninteresting extra errors (many saying "type annotations needed" when type inference fails), and in a few cases, due to delayed bugs causing ICEs when no normal errors are printed. To fix these, this commit adds `DiagCtxt::stashed_err_count`, and uses it in three places alongside `DiagCtxt::{has_errors,err_count}`. It's dodgy to rely on it, because unlike `DiagCtxt::err_count` it can go up and down. But it's needed to preserve existing behaviour, and at least the three places that need it are now obvious. --- compiler/rustc_interface/src/passes.rs | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'compiler/rustc_interface/src') diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs index 97956404120..50b2bf7da15 100644 --- a/compiler/rustc_interface/src/passes.rs +++ b/compiler/rustc_interface/src/passes.rs @@ -778,6 +778,10 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> { // kindck is gone now). -nmatsakis if let Some(reported) = sess.dcx().has_errors() { return Err(reported); + } else if sess.dcx().stashed_err_count() > 0 { + // Without this case we sometimes get delayed bug ICEs and I don't + // understand why. -nnethercote + return Err(sess.dcx().delayed_bug("some stashed error is waiting for use")); } sess.time("misc_checking_3", || { -- cgit 1.4.1-3-g733a5