hokein wrote: Thanks for implementing it!
I haven't looked into the implementation details yet. Before doing so, I want to ensure I understand the standard correctly (the standard's wording is a bit hard to follow). Per C++ [over.match.class.deduct#1.10](https://eel.is/c++draft/over.match.class.deduct#1.10): > In addition, if C is defined and inherits constructors > ([[namespace.udecl]](https://eel.is/c++draft/namespace.udecl)) from a direct > base class denoted in the > [base-specifier-list](https://eel.is/c++draft/class.derived.general#nt:base-specifier-list) > by a > [class-or-decltype](https://eel.is/c++draft/class.derived.general#nt:class-or-decltype) > B, let A be an alias template whose template parameter list is that of C and > whose > [defining-type-id](https://eel.is/c++draft/dcl.name#nt:defining-type-id) is > B[.](https://eel.is/c++draft/over.match.class.deduct#1.sentence-7) If A is a > deducible template > ([[dcl.type.simple]](https://eel.is/c++draft/dcl.type.simple)), the set > contains the guides of A with the return type R of each guide replaced with > typename CC<R>::type given a class template template <typename> class CC; whose primary template is not defined and with a single partial specialization whose template parameter list is that of A and whose template argument list is a specialization of A with the template argument list of A ([[temp.dep.type]](https://eel.is/c++draft/temp.dep.type)) having a member typedef type designating a template specialization with the template argument list of A but with C as the template[.](https://eel.is/c++draft/over.match.class.deduct#1.sentence-8) Let's use the following example to illustrate: ```cpp template <typename T1> struct B { B(T1); }; template <typename T2> struct C : public B<T2> { using B<T2>::B; }; ``` Here, `C` is the struct `C`, and `B` is `B<T2>`. ### Steps: 1. **Find the inherited constructor for class `C`:** `B(T1)`. 2. **Synthesize an alias template `A`:** `template<typename T2> using A = B<T2>;` 3. **Check if `A` is a deducible template per https://eel.is/c++draft/dcl.type.simple#3:** here A is deducible 4. **Synthesize the deduction guide for `A`:** the one we have interests is `auto (T2) -> B(T2)` 5. **Replace the return type with `CC<B<T2>>::type`:** ```cpp template <typename> class CC; template <typename T2> class CC<B<T2>> { public: typedef C<T2> type; }; ``` The we get the final deduction guide for C: `auto (T2) -> CC<B<T2>>::type`; https://github.com/llvm/llvm-project/pull/98788 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
