[interop] ensure C++ stdlib set's insert methods are unsafe

(cherry picked from commit 6c6092e)

Author: hyp

lib/ClangImporter/ClangDerivedConformances.cpp

@@ -565,6 +565,23 @@ void swift::conformToCxxSequenceIfNeeded(
   }
 }
 
+static bool isStdSetType(const clang::CXXRecordDecl *clangDecl) {
+  return isStdDecl(clangDecl, {"set", "unordered_set", "multiset"});
+}
+
+bool swift::isUnsafeStdMethod(const clang::CXXMethodDecl *methodDecl) {
+  auto parentDecl =
+      dyn_cast<clang::CXXRecordDecl>(methodDecl->getDeclContext());
+  if (!parentDecl)
+    return false;
+  if (!isStdSetType(parentDecl))
+    return false;
+  if (methodDecl->getDeclName().isIdentifier() &&
+      methodDecl->getName() == "insert")
+    return true;
+  return false;
+}
+
 void swift::conformToCxxSetIfNeeded(ClangImporter::Implementation &impl,
                                     NominalTypeDecl *decl,
                                     const clang::CXXRecordDecl *clangDecl) {
@@ -576,7 +593,7 @@ void swift::conformToCxxSetIfNeeded(ClangImporter::Implementation &impl,
 
   // Only auto-conform types from the C++ standard library. Custom user types
   // might have a similar interface but different semantics.
-  if (!isStdDecl(clangDecl, {"set", "unordered_set", "multiset"}))
+  if (!isStdSetType(clangDecl))
     return;
 
   auto valueType = lookupDirectSingleWithoutExtensions<TypeAliasDecl>(

lib/ClangImporter/ClangDerivedConformances.h

@@ -20,6 +20,8 @@ namespace swift {
 
 bool isIterator(const clang::CXXRecordDecl *clangDecl);
 
+bool isUnsafeStdMethod(const clang::CXXMethodDecl *methodDecl);
+
 /// If the decl is a C++ input iterator, synthesize a conformance to the
 /// UnsafeCxxInputIterator protocol, which is defined in the Cxx module.
 void conformToCxxIteratorIfNeeded(ClangImporter::Implementation &impl,

lib/ClangImporter/ClangImporter.cpp

@@ -6747,6 +6747,11 @@ bool IsSafeUseOfCxxDecl::evaluate(Evaluator &evaluator,
         method->getReturnType()->isReferenceType())
       return false;
 
+    // Check if it's one of the known unsafe methods we currently
+    // mark as safe by default.
+    if (isUnsafeStdMethod(method))
+      return false;
+
     // Try to figure out the semantics of the return type. If it's a
     // pointer/iterator, it's unsafe.
     if (auto returnType = dyn_cast<clang::RecordType>(