[clang] [clang][dataflow] Make optional checker work for types derived from optional. (PR #84138)

[Yitzhak Mandelbaum via cfe-commits]

================
@@ -64,39 +64,117 @@ static bool hasOptionalClassName(const CXXRecordDecl &RD) {
   return false;
 }
 
+static const CXXRecordDecl *getOptionalBaseClass(const CXXRecordDecl *RD) {
+  if (RD == nullptr)
+    return nullptr;
+  if (hasOptionalClassName(*RD))
+    return RD;
+
+  if (!RD->hasDefinition())
+    return nullptr;
+
+  for (const CXXBaseSpecifier &Base : RD->bases())
+    if (const CXXRecordDecl *BaseClass =
+            getOptionalBaseClass(Base.getType()->getAsCXXRecordDecl()))
+      return BaseClass;
+
+  return nullptr;
+}
+
 namespace {
 
 using namespace ::clang::ast_matchers;
 using LatticeTransferState = TransferState<NoopLattice>;
 
-AST_MATCHER(CXXRecordDecl, hasOptionalClassNameMatcher) {
-  return hasOptionalClassName(Node);
+AST_MATCHER(CXXRecordDecl, optionalClass) { return hasOptionalClassName(Node); }
+
+AST_MATCHER(CXXRecordDecl, optionalOrDerivedClass) {
+  return getOptionalBaseClass(&Node) != nullptr;
 }
 
-DeclarationMatcher optionalClass() {
-  return classTemplateSpecializationDecl(
-      hasOptionalClassNameMatcher(),
-      hasTemplateArgument(0, refersToType(type().bind("T"))));
+auto desugarsToOptionalType() {
+  return hasUnqualifiedDesugaredType(
+      recordType(hasDeclaration(cxxRecordDecl(optionalClass()))));
 }
 
-auto optionalOrAliasType() {
+auto desugarsToOptionalOrDerivedType() {
   return hasUnqualifiedDesugaredType(
-      recordType(hasDeclaration(optionalClass())));
+      recordType(hasDeclaration(cxxRecordDecl(optionalOrDerivedClass()))));
 }
 
-/// Matches any of the spellings of the optional types and sugar, aliases, etc.
-auto hasOptionalType() { return hasType(optionalOrAliasType()); }
+auto hasOptionalType() { return hasType(desugarsToOptionalType()); }
+
+/// Matches any of the spellings of the optional types and sugar, aliases,
+/// derived classes, etc.
+auto hasOptionalOrDerivedType() {
+  return hasType(desugarsToOptionalOrDerivedType());
+}
+
+QualType getPublicType(const Expr *E) {
+  auto *Cast = dyn_cast<ImplicitCastExpr>(E->IgnoreParens());
+  if (Cast == nullptr || Cast->getCastKind() != CK_UncheckedDerivedToBase) {
+    QualType Ty = E->getType();
+    if (Ty->isPointerType())
+      return Ty->getPointeeType();
+    return Ty;
+  }
+
+  QualType Ty = getPublicType(Cast->getSubExpr());
----------------
ymand wrote:

I don't understand this line. We're recursing, but then we throw away the result `Ty` based on how the loop turns out. Why not just test for this directly, after the loop and only recurse when the loop doesn't find what we want?  See more comments below, but perhaps the problem is that I don't really understand what the loop is doing.

https://github.com/llvm/llvm-project/pull/84138