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Mark fields used by debug format as used #124371

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Mark fields used by debug format as used #124371

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cc14f64
Mark fields used by debug format as used
long-long-float Apr 23, 2024
eb483cc
Fix safely
long-long-float Apr 25, 2024
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29 changes: 28 additions & 1 deletion compiler/rustc_passes/src/dead.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
// is dead.

use hir::def_id::{LocalDefIdMap, LocalDefIdSet};
use hir::ItemKind;
use hir::{ExprKind, ItemKind};
use rustc_data_structures::unord::UnordSet;
use rustc_errors::MultiSpan;
use rustc_hir as hir;
Expand Down Expand Up @@ -548,6 +548,33 @@ impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
self.handle_res(res);
}
hir::ExprKind::Call(callee, args) => {
// To avoid "never read" warnings for fields used by debugging format (":?"),
// check callee is format_argument::new_debug and mark the argument as "read".
if let Node::Expr(expr) = self.tcx.hir_node(callee.hir_id)
&& let ExprKind::Path(hir::QPath::TypeRelative(ty, new_debug_path)) = expr.kind
&& let TyKind::Path(hir::QPath::Resolved(_, path)) = ty.kind
&& let Some(def_id) = path.res.opt_def_id()
&& self.tcx.opt_item_name(def_id) == Some(sym::Argument)
&& let [segment] = path.segments
&& segment.ident.name == sym::format_argument
&& new_debug_path.ident.name == sym::new_debug
&& let [arg] = args
{
let arg_ty = self.typeck_results().expr_ty(arg);
if let Some(adt) = arg_ty.peel_refs().ty_adt_def()
&& adt.is_enum()
{
for variant in adt.variants() {
for field in &variant.fields {
if let Some(local_id) = field.did.as_local() {
self.live_symbols.insert(local_id);
}
}
}
}
}
}
hir::ExprKind::MethodCall(..) => {
self.lookup_and_handle_method(expr.hir_id);
}
Expand Down
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