[clang] [WebKit checkers] Recognize ensureFoo functions (PR #119681)

[Ryosuke Niwa via cfe-commits]

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@@ -169,4 +173,42 @@ bool isConstOwnerPtrMemberExpr(const clang::Expr *E) {
   return isOwnerPtrType(T) && T.isConstQualified();
 }
 
+class EnsureFunctionVisitor
+    : public ConstStmtVisitor<EnsureFunctionVisitor, bool> {
+public:
+  bool VisitStmt(const Stmt *S) {
+    for (const Stmt *Child : S->children()) {
+      if (Child && !Visit(Child))
+        return false;
+    }
+    return true;
+  }
+
+  bool VisitReturnStmt(const ReturnStmt *RS) {
+    if (auto *RV = RS->getRetValue()) {
+      RV = RV->IgnoreParenCasts();
+      if (isa<CXXNullPtrLiteralExpr>(RV))
+        return true;
+      return isConstOwnerPtrMemberExpr(RV);
+    }
+    return false;
+  }
+};
+
+bool EnsureFunctionAnalysis::isACallToEnsureFn(const clang::Expr *E) const {
+  auto *MCE = dyn_cast<CXXMemberCallExpr>(E);
+  if (!MCE)
+    return false;
+  auto *Callee = MCE->getDirectCallee();
+  if (!Callee)
+    return false;
+  auto *Body = Callee->getBody();
+  if (!Body)
+    return false;
+  auto [CacheIt, IsNew] = Cache.insert(std::make_pair(Callee, false));
+  if (IsNew)
+    CacheIt->second = EnsureFunctionVisitor().Visit(Body);
+  return CacheIt->second;
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rniwa wrote:

Yeah, I figured we should cache the result instead of keep analyzing the same function repeatedly.

https://github.com/llvm/llvm-project/pull/119681