[clang] [LifetimeSafety] Introduce buildOriginFlowChain for use-after-scope (PR #199345)

[Utkarsh Saxena via cfe-commits]

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@@ -471,13 +474,44 @@ class LifetimeSafetySemaHelperImpl : public LifetimeSafetySemaHelper {
   }
 
   std::string getDiagSubjectDescription(const Expr *E) {
+    E = E->IgnoreImpCasts();
     if (isa<MaterializeTemporaryExpr>(E))
       return "local temporary object";
 
     if (const auto *DRE = dyn_cast<DeclRefExpr>(E))
       return getDiagSubjectDescription(DRE->getDecl());
     // TODO: Handle other expression types.
-    return "";
+    return "expression";
+  }
+
+  bool shouldShowInAliasChain(const Expr *CurrExpr, const Expr *LastExpr) {
+    CurrExpr = CurrExpr->IgnoreImpCasts();
+    LastExpr = LastExpr->IgnoreImpCasts();
+
+    if (isa<MaterializeTemporaryExpr, ParenExpr>(CurrExpr))
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usx95 wrote:

I think we agreed to start from a small subset of expression like CallExpr and DeclRefExpr.

So we can have instead:
`if (!isa<CallExpr, DeclRefExpr>(CurrExpr)) return false;`

https://github.com/llvm/llvm-project/pull/199345