On 7/9/21 3:18 PM, Patrick Palka wrote:
This adds support for declaring (class-scope) deduction guides for a member class template. Fortunately it seems only a couple of changes are needed in order for the existing CTAD machinery to handle them like any other deduction guide: we need to make sure to give them a FUNCTION_TYPE instead of a METHOD_TYPE, and we need to avoid using a BASELINK when looking them up.Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk? PR c++/79501 gcc/cp/ChangeLog: * decl.c (grokfndecl): Don't require that deduction guides are declared at namespace scope. Check that class-scope deduction guides have the same access as the member class template. (grokdeclarator): Pretend class-scope deduction guides are static. * name-lookup.c (lookup_qualified_name): Don't use a BASELINK for class-scope deduction guides. gcc/testsuite/ChangeLog: * g++.dg/cpp1z/class-deduction92.C: New test. * g++.dg/cpp1z/class-deduction93.C: New test. * g++.dg/cpp1z/class-deduction94.C: New test. --- gcc/cp/decl.c | 17 ++++++++----- gcc/cp/name-lookup.c | 11 +++++--- .../g++.dg/cpp1z/class-deduction92.C | 16 ++++++++++++ .../g++.dg/cpp1z/class-deduction93.C | 25 +++++++++++++++++++ .../g++.dg/cpp1z/class-deduction94.C | 19 ++++++++++++++ 5 files changed, 79 insertions(+), 9 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction92.C create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction93.C create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction94.C diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index ebe1318d38d..8b8ffb7de83 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -10040,12 +10040,6 @@ grokfndecl (tree ctype,if (deduction_guide_p (decl)){ - if (!DECL_NAMESPACE_SCOPE_P (decl)) - { - error_at (location, "deduction guide %qD must be declared at " - "namespace scope", decl); - return NULL_TREE; - }
Do we still reject deduction guides at function scope?
tree type = TREE_TYPE (DECL_NAME (decl)); if (in_namespace == NULL_TREE && CP_DECL_CONTEXT (decl) != CP_TYPE_CONTEXT (type)) @@ -10055,6 +10049,13 @@ grokfndecl (tree ctype, inform (location_of (type), " declared here"); return NULL_TREE; } + if (DECL_CLASS_SCOPE_P (decl) + && current_access_specifier != declared_access (TYPE_NAME (type))) + { + error_at (location, "deduction guide %qD must have the same access " + "as %qT", decl, type); + inform (location_of (type), " declared here"); + } if (funcdef_flag) error_at (location, "deduction guide %qD must not have a function body", decl); @@ -12035,6 +12036,10 @@ grokdeclarator (const cp_declarator *declarator, storage_class = declspecs->storage_class; if (storage_class == sc_static) staticp = 1 + (decl_context == FIELD); + else if (decl_context == FIELD && sfk == sfk_deduction_guide) + /* Treat class-scope deduction guides as static member functions + so that they get a FUNCTION_TYPE instead of a METHOD_TYPE. */ + staticp = 2;if (virtualp){ diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c index 1be5f3da6d5..089bca1d471 100644 --- a/gcc/cp/name-lookup.c +++ b/gcc/cp/name-lookup.c @@ -7110,9 +7110,14 @@ lookup_qualified_name (tree scope, tree name, LOOK_want want, bool complain) else if (cxx_dialect != cxx98 && TREE_CODE (scope) == ENUMERAL_TYPE) t = lookup_enumerator (scope, name); else if (is_class_type (scope, complain)) - t = lookup_member (scope, name, 2, bool (want & LOOK_want::TYPE), - tf_warning_or_error); - + { + t = lookup_member (scope, name, 2, bool (want & LOOK_want::TYPE), + tf_warning_or_error); + if (t && dguide_name_p (name)) + /* Since class-scope deduction guides aren't really member functions, + don't use a BASELINK for them. */ + t = MAYBE_BASELINK_FUNCTIONS (t); + } if (!t) return error_mark_node; return t; diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction92.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction92.C new file mode 100644 index 00000000000..178234c76d1 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction92.C @@ -0,0 +1,16 @@ +// PR c++/79501 +// { dg-do compile { target c++17 } } + +template<auto V> +struct X { + template<class T> + struct B { T t; }; + + template<class T> B(T) -> B<const T>; + + auto foo() { return B{V}; } +}; + +X<42> x; +using type = decltype(x.foo()); +using type = X<42>::B<const int>; diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction93.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction93.C new file mode 100644 index 00000000000..9d2db7a55a2 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction93.C @@ -0,0 +1,25 @@ +// PR c++/79501 +// { dg-do compile { target c++17 } } +// A variant of class-deduction78.C where List and its deduction guides are +// defined at class scope. + +using size_t = decltype(sizeof(42)); + +struct A { + template<typename T, size_t N = 0> + struct List { + T head; + List<T, N-1> tail; + }; + + template<typename T> + struct List<T, 0> {}; + + template<typename T> List(T) -> List<T, 1>; + template<typename T, size_t N> List(T, List<T, N>) -> List<T, N+1>; +}; + +int main() { + using type = decltype(A::List{0, A::List{1, A::List{2}}}); + using type = A::List<int, 3>; +} diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction94.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction94.C new file mode 100644 index 00000000000..f29ebd2c2b8 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction94.C @@ -0,0 +1,19 @@ +// PR c++/79501 +// { dg-do compile { target c++17 } } + +struct X { +protected: + template<class T> + struct B { T t; }; + + template<class T> B(T) -> B<T>; +}; + +struct Y { +protected: + template<class T> + struct B { T t; }; + +private: + template<class T> B(T) -> B<T>; // { dg-error "access" } +};
