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"use of local which has no storage here" at -Zmir-opt-level=0 #144932
Description
I ran into this in my PR #131650 (comment) when trying to use GVN more, because MIR "lints" are enabled in the mir-opt suite.
This lint fires a fair bit in the ecosystem, for example in zvariant-5.6.0, compiling with RUSTFLAGS="-Zlint-mir -Zmir-opt-level=0 -Zmir-enable-passes=+GVN" cargo +nightly build
error: internal compiler error: broken MIR in Item(DefId(0:1107 ~ zvariant[4905]::dbus::ser::{impl#4}::serialize_struct_element)) (after pass SanityCheck) at bb46[0]:
use of local _10, which has no storage here
--> src/dbus/ser.rs:540:5
|
540 | }
| ^
|
note: delayed at compiler/rustc_mir_transform/src/lint.rs:74:22
0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
3: <rustc_errors::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, alloc::string::String>
4: <rustc_mir_transform::lint::Lint>::fail::<alloc::string::String>
5: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_local
6: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_place
7: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_terminator
8: rustc_mir_transform::lint::lint_body
9: rustc_mir_transform::mir_built
<snip>
Activity
cjgillot commentedon Aug 5, 2025
I'm puzzled by this issue.
SanityCheckruns just after MIR building. The only thing that happens earlier is aSimplifyCfg.saethlin commentedon Aug 5, 2025
Oh, hm. It's quite possible that in my hunt for this same error outside my PR I ran into a different problem.
[-]"use of local which has no storage here" caused by GVN[/-][+]"use of local which has no storage here" at -Zmir-opt-level=0[/+]saethlin commentedon Aug 6, 2025
Yeah this is definitely not the GVN issue I was hunting. It's a problem before opts.