[clang] [alpha.webkit.UnretainedCallArgsChecker] Recognize [allocObj() init] pattern (PR #161019)

[Ryosuke Niwa via cfe-commits]

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@@ -321,6 +321,51 @@ bool isExprToGetCheckedPtrCapableMember(const clang::Expr *E) {
   return result && *result;
 }
 
+bool isAllocInit(const Expr *E, const Expr **InnerExpr) {
+  auto *ObjCMsgExpr = dyn_cast<ObjCMessageExpr>(E);
+  if (auto *POE = dyn_cast<PseudoObjectExpr>(E)) {
+    if (unsigned ExprCount = POE->getNumSemanticExprs()) {
+      auto *Expr = POE->getSemanticExpr(ExprCount - 1)->IgnoreParenCasts();
----------------
rniwa wrote:

Right, and here too we check that `POE->getNumSemanticExprs()`'s return value is at least 1 by the if:
```cpp
if (unsigned ExprCount = POE->getNumSemanticExprs()) {
  // ExprCount is at least 1 here or else the above if condition will evaluate to false. 
  auto *Expr = POE->getSemanticExpr(ExprCount - 1)->IgnoreParenCasts();
```

https://github.com/llvm/llvm-project/pull/161019