Restore the SetType constructor and destructor

src/Type.cc

@@ -569,6 +569,50 @@ bool TableType::DoExpireCheck(const detail::AttrPtr& attr) {
     return true;
 }
 
+SetType::SetType(TypeListPtr ind, detail::ListExprPtr arg_elements)
+    : TableType(std::move(ind), nullptr), elements(std::move(arg_elements)) {
+    if ( elements ) {
+        if ( indices ) { // We already have a type.
+            if ( ! check_and_promote_exprs(elements.get(), indices) )
+                SetError();
+        }
+        else {
+            TypeList* tl_type = elements->GetType()->AsTypeList();
+            const auto& tl = tl_type->GetTypes();
+
+            if ( tl.size() < 1 ) {
+                Error("no type given for set");
+                SetError();
+            }
+
+            else if ( tl.size() == 1 ) {
+                TypePtr ft{NewRef{}, flatten_type(tl[0].get())};
+                indices = make_intrusive<TypeList>(ft);
+                indices->Append(std::move(ft));
+            }
+
+            else {
+                auto t = merge_types(tl[0], tl[1]);
+
+                for ( size_t i = 2; t && i < tl.size(); ++i )
+                    t = merge_types(t, tl[i]);
+
+                if ( ! t ) {
+                    Error("bad set type");
+                    return;
+                }
+
+                indices = make_intrusive<TypeList>(t);
+                indices->Append(std::move(t));
+            }
+        }
+    }
+}
+
+TypePtr SetType::ShallowClone() { return make_intrusive<SetType>(indices, elements); }
+
+SetType::~SetType() = default;
+
 FuncType::Capture::Capture(detail::IDPtr _id, bool _deep_copy) : id(std::move(_id)), deep_copy(_deep_copy) {
     is_managed = id ? ZVal::IsManagedType(id->GetType()) : false;
     if ( ! is_managed )