[clang] [LifetimeSafety] Suggest lifetime annotations (PR #169767)

[Utkarsh Saxena via cfe-commits]

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@@ -342,4 +347,27 @@ void FactsGenerator::markUseAsWrite(const DeclRefExpr *DRE) {
   UseFacts[DRE]->markAsWritten();
 }
 
+// Creates an IssueFact for a new placeholder loan for each pointer or reference
+// parameter at the function's entry.
+llvm::SmallVector<Fact *> FactsGenerator::createPlaceholderLoanFacts() {
+  llvm::SmallVector<Fact *> PlaceholderLoanFacts;
+  const auto *FD = dyn_cast<FunctionDecl>(AC.getDecl());
+  if (!FD)
+    return PlaceholderLoanFacts;
+
+  for (const ParmVarDecl *PVD : FD->parameters()) {
+    QualType ParamType = PVD->getType();
+    if (PVD->hasAttr<LifetimeBoundAttr>())
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usx95 wrote:

\+1. The reporting at the end should take care of not suggesting already annotated params instead of dropping the placeholder loans.

These loans would also help us improve C++ coverage metric: "Origins with no loans". It seems helpful to differentiate between the case when origins hold placeholders vs origins hold no loans (because of being either unknown of analysis bug). So these loans serve mutliple purposes beyond lifetime suggestions alone.

https://github.com/llvm/llvm-project/pull/169767