[clang] [NFC][LifetimeSafety]: Track assignment history within a single CFGBlock (PR #196075)

[Yuan Suo via cfe-commits]

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@@ -0,0 +1,186 @@
+//===- AssignmentQuery.cpp - C++ Lifetime Safety Checker --------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the LifetimeChecker, which detects use-after-free
+// errors by checking if live origins hold loans that have expired.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/Analyses/LifetimeSafety/AssignmentQuery.h"
+#include <optional>
+
+namespace {
+using namespace clang;
+using namespace clang::lifetimes;
+using namespace clang::lifetimes::internal;
+
+/// Locate the rightmost sub expression of the RHS, given that the LHS is
+/// already known. To ensure printability, we invoke `Explorc->isValid()`.
+///
+/// Typically, we select the rightmost subexpression, as it can be further
+/// decomposed and parsed recursively.
+///
+/// Since we are traversing assignments in reverse order, this function used
+/// to determines whether `TargetExpr` meets the requirements of the RHS.
+/// A match here triggers a subsequent attempt to match the LHS.
+/// Because the function is not re-invoked until the LHS is matched,
+/// it generally precludes the possibility of matching multiple
+/// subexpressions within the same RHS.
+const Expr *getRootSrcExpr(const Expr *TargetExpr) {
+  assert(TargetExpr);
+  const Expr *SExpr = TargetExpr->IgnoreParenCasts();
+
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suoyuan666 wrote:

I’m looking to preserve the valuable `Expr` nodes here, as I need them for subsequent `Sema` warning generation. Although this PR does not include the `Sema` diagnostic part.

https://github.com/llvm/llvm-project/pull/196075