[clang] [LifetimeSafety] Trace assignment history for use-after-scope errors (PR #188467)

[Utkarsh Saxena via cfe-commits]

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@@ -219,6 +227,194 @@ class LifetimeChecker {
     }
   }
 
+  std::optional<llvm::SmallVector<AssignmentPair>>
+  getAliasListInMultiBlock(const CFGBlock *StartBlock, const LoanID EndLoanID,
+                           OriginID *StartOID) {
+    const ValueDecl *LastDestDecl = nullptr;
+    llvm::SmallVector<const CFGBlock *> PendingBlocks;
+    std::optional<AssignmentPair> StartStmt = std::nullopt;
+    std::optional<AssignmentPair> EndStmt = std::nullopt;
+    std::optional<OriginID> LastOriginID = std::nullopt;
+    llvm::SmallPtrSet<const CFGBlock *, 32> VistedBlocks;
+    llvm::DenseMap<AssignmentPair, AssignmentPair> VistedExprs;
+
+    const auto AliasStmtFilter = [&VistedExprs](const AssignmentPair StartStmt,
+                                                const AssignmentPair EndStmt) {
+      llvm::SmallVector<AssignmentPair> AliasStmts;
+      for (auto Stmt = StartStmt; Stmt != EndStmt;
+           Stmt = VistedExprs.at(Stmt)) {
+        AliasStmts.push_back(Stmt);
+      }
+      AliasStmts.push_back(EndStmt);
+      return AliasStmts;
+    };
+
+    PendingBlocks.push_back(StartBlock);
+
+    for (size_t i = 0; i < PendingBlocks.size(); ++i) {
+      const CFGBlock *CurrBlock = PendingBlocks[i];
+
+      const auto [BlockAliasList, Success, CurrLastDestDecl, CurrLastOriginID] =
+          getAliasListCore(CurrBlock, EndLoanID, StartOID, LastDestDecl,
+                           LastOriginID);
+      if (CurrLastDestDecl)
+        LastDestDecl = CurrLastDestDecl;
+      if (CurrLastOriginID.has_value())
+        LastOriginID = CurrLastOriginID;
+
+      if (!BlockAliasList.empty()) {
+        if (VistedExprs.empty()) {
+          StartStmt = BlockAliasList[0];
+        }
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usx95 wrote:

nit: avoid braces for single-line bodies of `if` and `for` throughout the PR

https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

https://github.com/llvm/llvm-project/pull/188467