MIR validation: ensure that debuginfo records are not emitted for locals that are not in debuginfo

Author: dianqk

compiler/rustc_mir_transform/src/validate.rs

@@ -17,6 +17,7 @@ use rustc_middle::ty::{
     self, CoroutineArgsExt, InstanceKind, ScalarInt, Ty, TyCtxt, TypeVisitableExt, Upcast, Variance,
 };
 use rustc_middle::{bug, span_bug};
+use rustc_mir_dataflow::debuginfo::debuginfo_locals;
 use rustc_trait_selection::traits::ObligationCtxt;
 
 use crate::util::{self, is_within_packed};
@@ -80,6 +81,11 @@ impl<'tcx> crate::MirPass<'tcx> for Validator {
             cfg_checker.fail(location, msg);
         }
 
+        // Ensure that debuginfo records are not emitted for locals that are not in debuginfo.
+        for (location, msg) in validate_debuginfos(body) {
+            cfg_checker.fail(location, msg);
+        }
+
         if let MirPhase::Runtime(_) = body.phase
             && let ty::InstanceKind::Item(_) = body.source.instance
             && body.has_free_regions()
@@ -1595,3 +1601,30 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
         self.super_terminator(terminator, location);
     }
 }
+
+pub(super) fn validate_debuginfos<'tcx>(body: &Body<'tcx>) -> Vec<(Location, String)> {
+    let mut debuginfo_checker =
+        DebuginfoChecker { debuginfo_locals: debuginfo_locals(body), failures: Vec::new() };
+    debuginfo_checker.visit_body(body);
+    debuginfo_checker.failures
+}
+
+struct DebuginfoChecker {
+    debuginfo_locals: DenseBitSet<Local>,
+    failures: Vec<(Location, String)>,
+}
+
+impl<'tcx> Visitor<'tcx> for DebuginfoChecker {
+    fn visit_statement_debuginfo(
+        &mut self,
+        stmt_debuginfo: &StmtDebugInfo<'tcx>,
+        location: Location,
+    ) {
+        let local = match stmt_debuginfo {
+            StmtDebugInfo::AssignRef(local, _) | StmtDebugInfo::InvalidAssign(local) => *local,
+        };
+        if !self.debuginfo_locals.contains(local) {
+            self.failures.push((location, format!("{local:?} is not in debuginfo")));
+        }
+    }
+}