Address the remaining issues, so that this becomes ready for merge.

Signed-off-by: Johannes Kalmbach <[email protected]>

src/engine/idTable/CompressedExternalIdTable.h

@@ -22,13 +22,13 @@
 
 namespace ad_utility {
 
-namespace {
+namespace compressedExternalIdTable::detail {
 template <typename B, typename R>
 CPP_requires(HasPushBackRequires, requires(B& b, const R& r)(b.push_back(r)));
 
 template <typename B, typename R>
 CPP_concept HasPushBack = CPP_requires_ref(HasPushBackRequires, B, R);
-}
+}  // namespace compressedExternalIdTable::detail
 
 using namespace ad_utility::memory_literals;
 
@@ -347,9 +347,8 @@ class CompressedExternalIdTableBase {
   // Add a single row to the input. The type of `row` needs to be something that
   // can be `push_back`ed to a `IdTable`.
   CPP_template(typename R)(
-      requires HasPushBack<decltype(currentBlock_),
-                                  R>) void push(const R& row)
-  {
+      requires compressedExternalIdTable::detail::HasPushBack<
+          decltype(currentBlock_), R>) void push(const R& row) {
     ++numElementsPushed_;
     currentBlock_.push_back(row);
     if (currentBlock_.size() >= blocksize_) {

src/engine/idTable/IdTable.h

@@ -240,23 +240,26 @@ class IdTable {
   // `IdTables` are expensive to copy, so we disable accidental copies as they
   // are most likely bugs. To explicitly copy an `IdTable`, the `clone()` member
   // function (see below) can be used.
-  CPP_template(typename = void)(requires(!isView))
-      IdTable(const IdTable&) = delete;
-
-  CPP_template(typename = void)(requires(!isView)) IdTable& operator=(
-      const IdTable&) requires(!isView)
-  = delete;
-
+  // Note: We currently only disable the copy operations in C++20 mode.
+  // TODO<joka921> implement a facility (probably via inheritance) where we can
+  // also implement the deleted copy operations for C++17
 #ifndef QLEVER_CPP_17
+  IdTable(const IdTable&) requires(!isView) = delete;
+  IdTable& operator=(const IdTable&) requires(!isView) = delete;
+
   //  Views are copyable, as they are cheap to copy.
   IdTable(const IdTable&) requires isView = default;
   IdTable& operator=(const IdTable&) requires isView = default;
 
-  // `IdTable`s are movable
-  IdTable(IdTable&& other) noexcept requires(!isView) = default;
-  IdTable& operator=(IdTable&& other) noexcept requires(!isView) = default;
+#else
+  IdTable(const IdTable&) = default;
+  IdTable& operator=(const IdTable&) = default;
 #endif
 
+  // `IdTable`s are movable
+  IdTable(IdTable&& other) noexcept = default;
+  IdTable& operator=(IdTable&& other) noexcept = default;
+
  private:
   // Make the other instantiations of `IdTable` friends to allow for conversion
   // between them using a private interface.

src/util/StringUtils.h

@@ -113,7 +113,7 @@ CPP_template(typename Range)(
 
 // Similar to the overload of `lazyStrJoin` above, but the result is returned as
 // a string.
-CPP_template_def(typename Range)(
+CPP_template(typename Range)(
     requires ql::ranges::input_range<Range> CPP_and ad_utility::Streamable<
         std::iter_reference_t<ql::ranges::iterator_t<Range>>>) std::string
     lazyStrJoin(Range&& r, std::string_view separator);

test/IdTableTest.cpp

@@ -1101,6 +1101,8 @@ TEST(IdTable, staticAsserts) {
   static_assert(std::is_trivially_copyable_v<IdTableStatic<1>::const_iterator>);
   static_assert(ql::ranges::random_access_range<IdTable>);
   static_assert(ql::ranges::random_access_range<IdTableStatic<1>>);
+
+  static_assert(std::is_copy_constructible_v<IdTableView<1>>);
 }
 
 TEST(IdTable, constructorsAreSfinaeFriendly) {