Open Naserume opened 4 months ago
Indeed looks very similar to https://github.com/rust-lang/rust/issues/99852 which was fixed in https://github.com/rust-lang/rust/pull/102394.
Minimized:
#![feature(let_chains)]
struct Struct;
impl Drop for Struct {
fn drop(&mut self) {}
}
fn main() {
if true
&& let _ = Struct
{}
}
This is the first pass that errors:
error: internal compiler error: broken MIR in Item(DefId(0:7 ~ foo[b740]::main)) (after pass CheckPackedRef) at bb8[1]:
use of local _2, which has no storage here
Here's a MIR that errors, taken in a later phase for convenience:
error: internal compiler error: broken MIR in Item(DefId(0:7 ~ foo[b740]::main)) (after pass SimplifyCfg-pre-optimizations) at bb6[0]:
use of local _2, which has no storage here
// MIR for `main` after SimplifyCfg-pre-optimizations
fn main() -> () {
let mut _0: ();
let mut _1: bool;
let mut _2: Struct;
let mut _3: bool;
bb0: {
_3 = const false;
StorageLive(_1);
_1 = const true;
switchInt(move _1) -> [0: bb2, otherwise: bb1];
}
bb1: {
StorageLive(_2);
_3 = const true;
_2 = Struct;
_0 = const ();
goto -> bb3;
}
bb2: {
_0 = const ();
goto -> bb3;
}
bb3: {
StorageDead(_1);
switchInt(_3) -> [0: bb4, otherwise: bb6];
}
bb4: {
_3 = const false;
StorageDead(_2);
return;
}
bb5 (cleanup): {
resume;
}
bb6: {
drop(_2) -> [return: bb4, unwind: bb5];
}
}
version: 1.79.0-nightly (805813650 2024-03-31)
The error is pretty clear: when testing the boolean, if found false
we shortcut to bb2
which doesn't initialize the Struct
, but the Struct
is unconditionally dropped at the end of the if
block (in bb6
).
Indeed this no longer errors:
#![feature(let_chains)]
struct Struct;
impl Drop for Struct {
fn drop(&mut self) {}
}
fn main() {
let s = Struct;
if true
&& let _ = s
{}
}
Ah, this is actually an issue with -Zlint-mir
more than anything, since variations on this store a drop flag to ensure we only drop the value if it was initialized. There's no unsoundness here, just a validation phase that doesn't take into account drop flags.
Code
Meta
rustc --version --verbose
:Error output
command
rustc EDF91430837E67F42912F85F184235C09E30358C3D226F98C2B0098353056538.rs '-Zlint-mir'
full backtrace is very long (about 3000 lines) you can see it in here
Backtrace
``` error: internal compiler error: broken MIR in Item(DefId(0:3 ~ EDF91430837E67F42912F85F184235C09E30358C3D226F98C2B0098353056538[ff8a]::owned2)) (after pass CheckPackedRef) at bb29[0]: use of local _6, which has no storage here --> EDF91430837E67F42912F85F184235C09E30358C3D226F98C2B0098353056538.rs:18:1 | 18 | } | ^ | note: delayed at compiler/rustc_mir_transform/src/lint.rs:75:22 0: std::backtrace::Backtrace::create 1: std::backtrace::Backtrace::capture 2:::emit_diagnostic
3: ::emit_diagnostic
4: ::emit_producing_guarantee
5: ::span_delayed_bug::
6: ::fail::
7: ::visit_local
8: ::visit_terminator
9: rustc_mir_transform::lint::lint_body
10: rustc_mir_transform::pass_manager::run_passes_inner
11: rustc_mir_transform::mir_const
12: rustc_query_impl::plumbing::__rust_begin_short_backtrace::>
13: rustc_query_system::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
14: rustc_query_impl::query_impl::mir_const::get_query_non_incr::__rust_end_short_backtrace
15: rustc_middle::query::plumbing::query_get_at::>>
16: rustc_mir_transform::mir_promoted
17: rustc_query_impl::plumbing::__rust_begin_short_backtrace::>
18: >::call_once
19: rustc_query_system::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
20: rustc_query_impl::query_impl::mir_promoted::get_query_non_incr::__rust_end_short_backtrace
21: rustc_middle::query::plumbing::query_get_at::>>
22: rustc_borrowck::mir_borrowck
23: rustc_query_impl::plumbing::__rust_begin_short_backtrace::>
24: rustc_query_system::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
25: rustc_query_impl::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
26: ::par_body_owners::::{closure#0}
27: rustc_interface::passes::analysis
28: rustc_query_impl::plumbing::__rust_begin_short_backtrace::>
29: rustc_query_system::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
30: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
31: >::enter::, rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure#3}>
32: rustc_interface::interface::run_compiler::, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}
33: std::sys_common::backtrace::__rust_begin_short_backtrace::, 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>>
34: <::spawn_unchecked_, 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}
35: std::sys::pal::unix::thread::Thread::new::thread_start
36: __pthread_start
--> EDF91430837E67F42912F85F184235C09E30358C3D226F98C2B0098353056538.rs:18:1
|
18 | }
| ^
error: internal compiler error: broken MIR in Item(DefId(0:3 ~ EDF91430837E67F42912F85F184235C09E30358C3D226F98C2B0098353056538[ff8a]::owned2)) (after pass CheckPackedRef) at bb24[1]:
use of local _6, which has no storage here
--> EDF91430837E67F42912F85F184235C09E30358C3D226F98C2B0098353056538.rs:18:1
|
18 | }
| ^
|
note: delayed at compiler/rustc_mir_transform/src/lint.rs:75:22
0: std::backtrace::Backtrace::create
1: std::backtrace::Backtrace::capture
2: ::emit_diagnostic
3: ::emit_diagnostic
4: ::emit_producing_guarantee
5: ::span_delayed_bug::
6: ::fail::
7: ::visit_local
8: ::visit_terminator
9: rustc_mir_transform::lint::lint_body
10: rustc_mir_transform::pass_manager::run_passes_inner
11: rustc_mir_transform::mir_const
12: rustc_query_impl::plumbing::__rust_begin_short_backtrace::>
13: rustc_query_system::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
14: rustc_query_impl::query_impl::mir_const::get_query_non_incr::__rust_end_short_backtrace
15: rustc_middle::query::plumbing::query_get_at::>>
16: rustc_mir_transform::mir_promoted
17: rustc_query_impl::plumbing::__rust_begin_short_backtrace::>
18: >::call_once
19: rustc_query_system::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
20: rustc_query_impl::query_impl::mir_promoted::get_query_non_incr::__rust_end_short_backtrace
21: rustc_middle::query::plumbing::query_get_at::>>
22: rustc_borrowck::mir_borrowck
23: rustc_query_impl::plumbing::__rust_begin_short_backtrace::>
24: rustc_query_system::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
25: rustc_query_impl::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
26: ::par_body_owners::::{closure#0}
27: rustc_interface::passes::analysis
28: rustc_query_impl::plumbing::__rust_begin_short_backtrace::>
29: rustc_query_system::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
30: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
31: >::enter::, rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure#3}>
32: rustc_interface::interface::run_compiler::, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}
33: std::sys_common::backtrace::__rust_begin_short_backtrace::, 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>>
34: <::spawn_unchecked_, 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}
35: std::sys::pal::unix::thread::Thread::new::thread_start
36: __pthread_start
--> EDF91430837E67F42912F85F184235C09E30358C3D226F98C2B0098353056538.rs:18:1
|
18 | }
| ^
```
seems like bug occured at visit_local and it's different one from #120421 visit_statement and visit_terminator