* [PATCH] c++: permit deduction guides at class scope [PR79501]
@ 2021-07-09 19:18 Patrick Palka
2021-07-09 19:54 ` Jason Merrill
0 siblings, 1 reply; 8+ messages in thread
From: Patrick Palka @ 2021-07-09 19:18 UTC (permalink / raw)
To: gcc-patches
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;
- }
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" }
+};
--
2.32.0.170.gd486ca60a5
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] c++: permit deduction guides at class scope [PR79501]
2021-07-09 19:18 [PATCH] c++: permit deduction guides at class scope [PR79501] Patrick Palka
@ 2021-07-09 19:54 ` Jason Merrill
2021-07-09 20:06 ` Patrick Palka
0 siblings, 1 reply; 8+ messages in thread
From: Jason Merrill @ 2021-07-09 19:54 UTC (permalink / raw)
To: Patrick Palka, gcc-patches
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" }
> +};
>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] c++: permit deduction guides at class scope [PR79501]
2021-07-09 19:54 ` Jason Merrill
@ 2021-07-09 20:06 ` Patrick Palka
2021-07-09 20:18 ` Patrick Palka
0 siblings, 1 reply; 8+ messages in thread
From: Patrick Palka @ 2021-07-09 20:06 UTC (permalink / raw)
To: Jason Merrill; +Cc: Patrick Palka, gcc-patches
On Fri, 9 Jul 2021, Jason Merrill wrote:
> 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?
Yes, it looks like the parser doesn't even recognize them at function scope:
template<class T> struct A;
int main() {
A(int) -> A<int>;
}
<stdin>:4:4: error: missing template arguments before ‘(’ token
<stdin>:4:5: error: expected primary-expression before ‘int’
<stdin>:4:13: error: invalid use of ‘struct A<int>’
Deduction guide templates are also still rejected (as with all templates 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" }
> > +};
> >
>
>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] c++: permit deduction guides at class scope [PR79501]
2021-07-09 20:06 ` Patrick Palka
@ 2021-07-09 20:18 ` Patrick Palka
2021-07-09 20:41 ` Marek Polacek
2021-07-09 21:32 ` Jason Merrill
0 siblings, 2 replies; 8+ messages in thread
From: Patrick Palka @ 2021-07-09 20:18 UTC (permalink / raw)
To: Patrick Palka; +Cc: Jason Merrill, gcc-patches
On Fri, 9 Jul 2021, Patrick Palka wrote:
> On Fri, 9 Jul 2021, Jason Merrill wrote:
>
> > 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?
>
> Yes, it looks like the parser doesn't even recognize them at function scope:
>
> template<class T> struct A;
>
> int main() {
> A(int) -> A<int>;
> }
>
> <stdin>:4:4: error: missing template arguments before ‘(’ token
> <stdin>:4:5: error: expected primary-expression before ‘int’
> <stdin>:4:13: error: invalid use of ‘struct A<int>’
>
> Deduction guide templates are also still rejected (as with all templates 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);
> > > + }
On second thought, this seems to be an awkward spot to do this
adjustment. Maybe it's better to do it in lookup_member, or in
deduction_guides_for (the only caller which really needs it)?
> > > 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" }
> > > +};
> > >
> >
> >
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] c++: permit deduction guides at class scope [PR79501]
2021-07-09 20:18 ` Patrick Palka
@ 2021-07-09 20:41 ` Marek Polacek
2021-07-09 21:32 ` Jason Merrill
1 sibling, 0 replies; 8+ messages in thread
From: Marek Polacek @ 2021-07-09 20:41 UTC (permalink / raw)
To: Patrick Palka; +Cc: gcc-patches
On Fri, Jul 09, 2021 at 04:18:34PM -0400, Patrick Palka via Gcc-patches wrote:
> > > > --- 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);
> > > > + }
>
> On second thought, this seems to be an awkward spot to do this
> adjustment. Maybe it's better to do it in lookup_member, or in
> deduction_guides_for (the only caller which really needs it)?
Yeah, doing it in deduction_guides_for sounds a bit better to me.
Marek
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] c++: permit deduction guides at class scope [PR79501]
2021-07-09 20:18 ` Patrick Palka
2021-07-09 20:41 ` Marek Polacek
@ 2021-07-09 21:32 ` Jason Merrill
2021-07-09 22:41 ` Patrick Palka
1 sibling, 1 reply; 8+ messages in thread
From: Jason Merrill @ 2021-07-09 21:32 UTC (permalink / raw)
To: Patrick Palka; +Cc: gcc-patches
On 7/9/21 4:18 PM, Patrick Palka wrote:
> On Fri, 9 Jul 2021, Patrick Palka wrote:
>
>> On Fri, 9 Jul 2021, Jason Merrill wrote:
>>
>>> 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?
>>
>> Yes, it looks like the parser doesn't even recognize them at function scope:
>>
>> template<class T> struct A;
>>
>> int main() {
>> A(int) -> A<int>;
>> }
>>
>> <stdin>:4:4: error: missing template arguments before ‘(’ token
>> <stdin>:4:5: error: expected primary-expression before ‘int’
>> <stdin>:4:13: error: invalid use of ‘struct A<int>’
>>
>> Deduction guide templates are also still rejected (as with all templates 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);
>>>> + }
>
> On second thought, this seems to be an awkward spot to do this
> adjustment. Maybe it's better to do it in lookup_member, or in
> deduction_guides_for (the only caller which really needs it)?
Avoiding building the baselink in lookup_member does sound better than
stripping it again here.
>>>> 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" }
>>>> +};
>>>>
>>>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] c++: permit deduction guides at class scope [PR79501]
2021-07-09 21:32 ` Jason Merrill
@ 2021-07-09 22:41 ` Patrick Palka
2021-07-12 19:41 ` Jason Merrill
0 siblings, 1 reply; 8+ messages in thread
From: Patrick Palka @ 2021-07-09 22:41 UTC (permalink / raw)
To: Jason Merrill; +Cc: Patrick Palka, gcc-patches
On Fri, 9 Jul 2021, Jason Merrill wrote:
> On 7/9/21 4:18 PM, Patrick Palka wrote:
> > On Fri, 9 Jul 2021, Patrick Palka wrote:
> >
> > > On Fri, 9 Jul 2021, Jason Merrill wrote:
> > >
> > > > 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?
> > >
> > > Yes, it looks like the parser doesn't even recognize them at function
> > > scope:
> > >
> > > template<class T> struct A;
> > >
> > > int main() {
> > > A(int) -> A<int>;
> > > }
> > >
> > > <stdin>:4:4: error: missing template arguments before ‘(’ token
> > > <stdin>:4:5: error: expected primary-expression before ‘int’
> > > <stdin>:4:13: error: invalid use of ‘struct A<int>’
> > >
> > > Deduction guide templates are also still rejected (as with all templates
> > > 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);
> > > > > + }
> >
> > On second thought, this seems to be an awkward spot to do this
> > adjustment. Maybe it's better to do it in lookup_member, or in
> > deduction_guides_for (the only caller which really needs it)?
>
> Avoiding building the baselink in lookup_member does sound better than
> stripping it again here.
That works well, like so? I also added the testcase from PR100983.
Bootstrapped and regtested on x86_64-pc-linux-gnu.
-- >8 --
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.
---
gcc/cp/decl.c | 17 ++++++++-----
gcc/cp/search.c | 5 +++-
.../g++.dg/cpp1z/class-deduction92.C | 16 ++++++++++++
.../g++.dg/cpp1z/class-deduction93.C | 25 +++++++++++++++++++
.../g++.dg/cpp1z/class-deduction94.C | 19 ++++++++++++++
.../g++.dg/cpp1z/class-deduction95.C | 13 ++++++++++
6 files changed, 88 insertions(+), 7 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
create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction95.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;
- }
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/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..78e76a6ab7b
--- /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, auto>
+ struct B { T t; };
+
+ template<class T> B(T, int=V) -> B<const T, V>;
+
+ auto foo() { return B{V}; }
+};
+
+X<42> x;
+using type = decltype(x.foo());
+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..afeb4a0d136
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction95.C
@@ -0,0 +1,13 @@
+// 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};
--
2.32.0.170.gd486ca60a5
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] c++: permit deduction guides at class scope [PR79501]
2021-07-09 22:41 ` Patrick Palka
@ 2021-07-12 19:41 ` Jason Merrill
0 siblings, 0 replies; 8+ messages in thread
From: Jason Merrill @ 2021-07-12 19:41 UTC (permalink / raw)
To: Patrick Palka; +Cc: gcc-patches
On 7/9/21 6:41 PM, Patrick Palka wrote:
> On Fri, 9 Jul 2021, Jason Merrill wrote:
>
>> On 7/9/21 4:18 PM, Patrick Palka wrote:
>>> On Fri, 9 Jul 2021, Patrick Palka wrote:
>>>
>>>> On Fri, 9 Jul 2021, Jason Merrill wrote:
>>>>
>>>>> 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?
>>>>
>>>> Yes, it looks like the parser doesn't even recognize them at function
>>>> scope:
>>>>
>>>> template<class T> struct A;
>>>>
>>>> int main() {
>>>> A(int) -> A<int>;
>>>> }
>>>>
>>>> <stdin>:4:4: error: missing template arguments before ‘(’ token
>>>> <stdin>:4:5: error: expected primary-expression before ‘int’
>>>> <stdin>:4:13: error: invalid use of ‘struct A<int>’
>>>>
>>>> Deduction guide templates are also still rejected (as with all templates
>>>> 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);
>>>>>> + }
>>>
>>> On second thought, this seems to be an awkward spot to do this
>>> adjustment. Maybe it's better to do it in lookup_member, or in
>>> deduction_guides_for (the only caller which really needs it)?
>>
>> Avoiding building the baselink in lookup_member does sound better than
>> stripping it again here.
>
> That works well, like so? I also added the testcase from PR100983.
> Bootstrapped and regtested on x86_64-pc-linux-gnu.
OK.
> -- >8 --
>
> 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.
> ---
> gcc/cp/decl.c | 17 ++++++++-----
> gcc/cp/search.c | 5 +++-
> .../g++.dg/cpp1z/class-deduction92.C | 16 ++++++++++++
> .../g++.dg/cpp1z/class-deduction93.C | 25 +++++++++++++++++++
> .../g++.dg/cpp1z/class-deduction94.C | 19 ++++++++++++++
> .../g++.dg/cpp1z/class-deduction95.C | 13 ++++++++++
> 6 files changed, 88 insertions(+), 7 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
> create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction95.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;
> - }
> 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/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..78e76a6ab7b
> --- /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, auto>
> + struct B { T t; };
> +
> + template<class T> B(T, int=V) -> B<const T, V>;
> +
> + auto foo() { return B{V}; }
> +};
> +
> +X<42> x;
> +using type = decltype(x.foo());
> +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..afeb4a0d136
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction95.C
> @@ -0,0 +1,13 @@
> +// 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};
>
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2021-07-12 19:41 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-09 19:18 [PATCH] c++: permit deduction guides at class scope [PR79501] Patrick Palka
2021-07-09 19:54 ` Jason Merrill
2021-07-09 20:06 ` Patrick Palka
2021-07-09 20:18 ` Patrick Palka
2021-07-09 20:41 ` Marek Polacek
2021-07-09 21:32 ` Jason Merrill
2021-07-09 22:41 ` Patrick Palka
2021-07-12 19:41 ` Jason Merrill
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