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* [gcc r12-2260] c++: permit deduction guides at class scope [PR79501]
@ 2021-07-12 20:35 Patrick Palka
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From: Patrick Palka @ 2021-07-12 20:35 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:8d75b8830e9dafb4e0c400c723653512adf40295
commit r12-2260-g8d75b8830e9dafb4e0c400c723653512adf40295
Author: Patrick Palka <ppalka@redhat.com>
Date: Mon Jul 12 16:35:18 2021 -0400
c++: permit deduction guides at class scope [PR79501]
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
properly: 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.
PR c++/79501
PR c++/100983
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.
* search.c (lookup_member): 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.
* g++.dg/cpp1z/class-deduction95.C: New test.
Diff:
---
gcc/cp/decl.c | 17 +++++++++++------
gcc/cp/search.c | 5 ++++-
gcc/testsuite/g++.dg/cpp1z/class-deduction92.C | 17 +++++++++++++++++
gcc/testsuite/g++.dg/cpp1z/class-deduction93.C | 25 +++++++++++++++++++++++++
gcc/testsuite/g++.dg/cpp1z/class-deduction94.C | 19 +++++++++++++++++++
gcc/testsuite/g++.dg/cpp1z/class-deduction95.C | 11 +++++++++++
6 files changed, 87 insertions(+), 7 deletions(-)
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 0df689b01f8..01d64a16125 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -10042,12 +10042,6 @@ 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;
- }
tree type = TREE_TYPE (DECL_NAME (decl));
if (in_namespace == NULL_TREE
&& CP_DECL_CONTEXT (decl) != CP_TYPE_CONTEXT (type))
@@ -10057,6 +10051,13 @@ 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);
@@ -12037,6 +12038,10 @@ 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/search.c b/gcc/cp/search.c
index 7b183685476..af41bfe5835 100644
--- a/gcc/cp/search.c
+++ b/gcc/cp/search.c
@@ -1226,7 +1226,10 @@ lookup_member (tree xbasetype, tree name, int protect, bool want_type,
rval = error_mark_node;
}
- if (rval && is_overloaded_fn (rval))
+ if (rval && is_overloaded_fn (rval)
+ /* Don't use a BASELINK for class-scope deduction guides since
+ they're not actually member functions. */
+ && !dguide_name_p (name))
rval = build_baselink (rval_binfo, basetype_path, rval,
(IDENTIFIER_CONV_OP_P (name)
? TREE_TYPE (name): NULL_TREE));
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..4920ca4f4a0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction92.C
@@ -0,0 +1,17 @@
+// PR c++/79501
+// { dg-do compile { target c++17 } }
+
+template<auto V>
+struct X {
+ template<class T, auto>
+ struct B { T t; };
+
+ template<class T> B(T, decltype(V)=V) -> B<const T, V>;
+
+ auto foo() { return B{V}; }
+};
+
+X<42> x;
+using type = decltype(x.foo());
+using type = decltype(decltype(x)::B{42});
+using type = X<42>::B<const int, 42>;
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" }
+};
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction95.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction95.C
new file mode 100644
index 00000000000..05cbb2babfe
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction95.C
@@ -0,0 +1,11 @@
+// PR c++/100983
+// { dg-do compile { target c++17 } }
+
+struct X {
+ template<int N>
+ struct Y { template<class... Ts> Y(Ts...); };
+
+ template<class... Ts> Y(Ts...) -> Y<sizeof...(Ts)>;
+};
+
+X::Y y{1,2,3};
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