[clang] [LifetimeSafety] Detect use-after-return (PR #165370)

[Utkarsh Saxena via cfe-commits]

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@@ -112,8 +114,17 @@ class LifetimeChecker {
     for (const auto &[LID, Warning] : FinalWarningsMap) {
       const Loan &L = FactMgr.getLoanMgr().getLoan(LID);
       const Expr *IssueExpr = L.IssueExpr;
-      Reporter->reportUseAfterFree(IssueExpr, Warning.UseExpr,
-                                   Warning.ExpiryLoc, Warning.ConfidenceLevel);
+      const Fact *CausingFact = Warning.CausingFact;
+      Confidence Confidence = Warning.ConfidenceLevel;
+      SourceLocation ExpiryLoc = Warning.ExpiryLoc;
+
+      if (const auto *UF = CausingFact->getAs<UseFact>()) {
+        Reporter->reportUseAfterFree(IssueExpr, UF->getUseExpr(), ExpiryLoc,
+                                     Confidence);
+      } else if (const auto *OEF = CausingFact->getAs<OriginEscapesFact>()) {
+        Reporter->reportUseAfterReturn(IssueExpr, OEF->getEscapeExpr(),
+                                       ExpiryLoc, Confidence);
+      }
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usx95 wrote:

add a final `else` with `llvm_unreachable("unhandled causing fact");`

https://github.com/llvm/llvm-project/pull/165370