[PATCH] c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

[PATCH] c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

[Patrick Palka]

r13-6098-g46711ff8e60d64 made make_typename_type no longer ignore
non-types during the lookup, unless the TYPENAME_TYPE in question was
followed by the :: scope resolution operator.  But there is another
exception to this rule: we need to ignore non-types during the lookup
also if the TYPENAME_TYPE was named with a tag other than 'typename',
such as 'struct' or 'enum', as per [dcl.type.elab]/5.

This patch implements this additional exception.  It occurred to me that
the tf_qualifying_scope flag is probably unnecessary if we'd use the
scope_type tag more thoroughly, but that requires parser changes that
are probably too risky at this stage.  (I'm working on addressing the
FIXME/TODOs here for GCC 14.)

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?

	PR c++/109420

gcc/cp/ChangeLog:

	* decl.cc (make_typename_type): Also ignore non-types during
	the lookup if tag_type is something other than none_type or
	typename_type.
	* pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
	enum_type as tag_type to make_typename_type as appropriate
	instead of always passing typename_type.

gcc/testsuite/ChangeLog:

	* g++.dg/template/typename27.C: New test.
---
 gcc/cp/decl.cc                             |  9 ++++++++-
 gcc/cp/pt.cc                               |  9 ++++++++-
 gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
 3 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/typename27.C

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 5369714f9b3..a0a20c5accc 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -4307,7 +4307,14 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
      lookup will stop when we hit a dependent base.  */
   if (!dependent_scope_p (context))
     {
-      bool want_type = (complain & tf_qualifying_scope);
+      /* As per [dcl.type.elab]/5 and [temp.res.general]/3, ignore non-types if
+	 the tag corresponds to a class-key or 'enum' (or is scope_type), or if
+	 this typename is followed by :: as per [basic.lookup.qual.general]/1.
+	 TODO: If we'd set the scope_type tag accurately on all TYPENAME_TYPEs
+	 that are followed by :: then we wouldn't need the tf_qualifying_scope
+	 flag.  */
+      bool want_type = (tag_type != none_type && tag_type != typename_type)
+	|| (complain & tf_qualifying_scope);
       t = lookup_member (context, name, /*protect=*/2, want_type, complain);
     }
   else
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 821e0035c08..1e778e6e786 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -16580,9 +16580,16 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	      return error_mark_node;
 	  }
 
+	/* FIXME: TYPENAME_IS_CLASS_P conflates 'union' vs 'struct' vs 'class'
+	   tags.  TYPENAME_TYPE should probably remember the exact tag that
+	   was used.  */
+	enum tag_types tag
+	  = TYPENAME_IS_CLASS_P (t) ? class_type
+	  : TYPENAME_IS_ENUM_P (t) ? enum_type
+	  : typename_type;
 	tsubst_flags_t tcomplain = complain | tf_keep_type_decl;
 	tcomplain |= tst_ok_flag | qualifying_scope_flag;
-	f = make_typename_type (ctx, f, typename_type, tcomplain);
+	f = make_typename_type (ctx, f, tag, tcomplain);
 	if (f == error_mark_node)
 	  return f;
 	if (TREE_CODE (f) == TYPE_DECL)
diff --git a/gcc/testsuite/g++.dg/template/typename27.C b/gcc/testsuite/g++.dg/template/typename27.C
new file mode 100644
index 00000000000..61b3efd998e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/typename27.C
@@ -0,0 +1,19 @@
+// PR c++/109420
+
+struct A {
+  struct X { };
+  int X;
+};
+
+struct B {
+  enum E { };
+  enum F { E };
+};
+
+template<class T, class U>
+void f() {
+  struct T::X x; // OK, lookup ignores the data member 'int A::X'
+  enum U::E e;   // OK, lookup ignores the enumerator 'B::F::E'
+}
+
+template void f<A, B>();
-- 
2.40.0.153.g6369acd968

Re: [PATCH] c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

[Patrick Palka]

On Wed, 5 Apr 2023, Patrick Palka wrote:

> r13-6098-g46711ff8e60d64 made make_typename_type no longer ignore
> non-types during the lookup, unless the TYPENAME_TYPE in question was
> followed by the :: scope resolution operator.  But there is another
> exception to this rule: we need to ignore non-types during the lookup
> also if the TYPENAME_TYPE was named with a tag other than 'typename',
> such as 'struct' or 'enum', as per [dcl.type.elab]/5.
> 
> This patch implements this additional exception.  It occurred to me that
> the tf_qualifying_scope flag is probably unnecessary if we'd use the
> scope_type tag more thoroughly, but that requires parser changes that
> are probably too risky at this stage.  (I'm working on addressing the
> FIXME/TODOs here for GCC 14.)
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?
> 
> 	PR c++/109420
> 
> gcc/cp/ChangeLog:
> 
> 	* decl.cc (make_typename_type): Also ignore non-types during
> 	the lookup if tag_type is something other than none_type or
> 	typename_type.
> 	* pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> 	enum_type as tag_type to make_typename_type as appropriate
> 	instead of always passing typename_type.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/template/typename27.C: New test.
> ---
>  gcc/cp/decl.cc                             |  9 ++++++++-
>  gcc/cp/pt.cc                               |  9 ++++++++-
>  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
>  3 files changed, 35 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> 
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 5369714f9b3..a0a20c5accc 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -4307,7 +4307,14 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
>       lookup will stop when we hit a dependent base.  */
>    if (!dependent_scope_p (context))
>      {
> -      bool want_type = (complain & tf_qualifying_scope);
> +      /* As per [dcl.type.elab]/5 and [temp.res.general]/3, ignore non-types if
> +	 the tag corresponds to a class-key or 'enum' (or is scope_type), or if
> +	 this typename is followed by :: as per [basic.lookup.qual.general]/1.
> +	 TODO: If we'd set the scope_type tag accurately on all TYPENAME_TYPEs
> +	 that are followed by :: then we wouldn't need the tf_qualifying_scope
> +	 flag.  */
> +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> +	|| (complain & tf_qualifying_scope);

Here's v2 which just slightly improves this comment.  I reckon [basic.lookup.elab]
is a better reference than [dcl.type.elab]/5 for justifying why the
lookup should be type-only for class-key and 'enum' TYPENAME_TYPEs.

-- >8 --

	PR c++/109420

gcc/cp/ChangeLog:

	* decl.cc (make_typename_type): Also ignore non-types during the
	lookup if tag_type corresponds to an elaborated-type-specifier.
	* pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
	enum_type as tag_type to make_typename_type as appropriate
	instead of always passing typename_type.

gcc/testsuite/ChangeLog:

	* g++.dg/template/typename27.C: New test.
---
 gcc/cp/decl.cc                             | 12 +++++++++++-
 gcc/cp/pt.cc                               |  9 ++++++++-
 gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
 3 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/typename27.C

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 5369714f9b3..772c059dc2c 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -4307,7 +4307,17 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
      lookup will stop when we hit a dependent base.  */
   if (!dependent_scope_p (context))
     {
-      bool want_type = (complain & tf_qualifying_scope);
+      /* We generally don't ignore non-types during TYPENAME_TYPE lookup
+	 (as per [temp.res.general]/3), unless
+	   - the tag corresponds to a class-key or 'enum' so
+	     [basic.lookup.elab] applies, or
+	   - the tag corresponds to scope_type or tf_qualifying_scope is
+	     set so [basic.lookup.qual]/1 applies.
+	 TODO: If we'd set/track the scope_type tag thoroughly on all
+	 TYPENAME_TYPEs that are followed by :: then we wouldn't need the
+	 tf_qualifying_scope flag.  */
+      bool want_type = (tag_type != none_type && tag_type != typename_type)
+	|| (complain & tf_qualifying_scope);
       t = lookup_member (context, name, /*protect=*/2, want_type, complain);
     }
   else
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 821e0035c08..09559c88f29 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -16580,9 +16580,16 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	      return error_mark_node;
 	  }
 
+	/* FIXME: TYPENAME_IS_CLASS_P conflates 'union' vs 'struct' vs 'class'
+	   tags.  TYPENAME_TYPE should probably remember the exact tag that
+	   was written.  */
+	enum tag_types tag
+	  = TYPENAME_IS_CLASS_P (t) ? class_type
+	  : TYPENAME_IS_ENUM_P (t) ? enum_type
+	  : typename_type;
 	tsubst_flags_t tcomplain = complain | tf_keep_type_decl;
 	tcomplain |= tst_ok_flag | qualifying_scope_flag;
-	f = make_typename_type (ctx, f, typename_type, tcomplain);
+	f = make_typename_type (ctx, f, tag, tcomplain);
 	if (f == error_mark_node)
 	  return f;
 	if (TREE_CODE (f) == TYPE_DECL)
diff --git a/gcc/testsuite/g++.dg/template/typename27.C b/gcc/testsuite/g++.dg/template/typename27.C
new file mode 100644
index 00000000000..61b3efd998e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/typename27.C
@@ -0,0 +1,19 @@
+// PR c++/109420
+
+struct A {
+  struct X { };
+  int X;
+};
+
+struct B {
+  enum E { };
+  enum F { E };
+};
+
+template<class T, class U>
+void f() {
+  struct T::X x; // OK, lookup ignores the data member 'int A::X'
+  enum U::E e;   // OK, lookup ignores the enumerator 'B::F::E'
+}
+
+template void f<A, B>();
-- 
2.40.0.153.g6369acd968

Re: [PATCH] c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

[Andrew Pinski]

On Wed, Apr 5, 2023 at 10:32 AM Patrick Palka via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Wed, 5 Apr 2023, Patrick Palka wrote:
>
> > r13-6098-g46711ff8e60d64 made make_typename_type no longer ignore
> > non-types during the lookup, unless the TYPENAME_TYPE in question was
> > followed by the :: scope resolution operator.  But there is another
> > exception to this rule: we need to ignore non-types during the lookup
> > also if the TYPENAME_TYPE was named with a tag other than 'typename',
> > such as 'struct' or 'enum', as per [dcl.type.elab]/5.
> >
> > This patch implements this additional exception.  It occurred to me that
> > the tf_qualifying_scope flag is probably unnecessary if we'd use the
> > scope_type tag more thoroughly, but that requires parser changes that
> > are probably too risky at this stage.  (I'm working on addressing the
> > FIXME/TODOs here for GCC 14.)
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk?
> >
> >       PR c++/109420
> >
> > gcc/cp/ChangeLog:
> >
> >       * decl.cc (make_typename_type): Also ignore non-types during
> >       the lookup if tag_type is something other than none_type or
> >       typename_type.
> >       * pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> >       enum_type as tag_type to make_typename_type as appropriate
> >       instead of always passing typename_type.
> >
> > gcc/testsuite/ChangeLog:
> >
> >       * g++.dg/template/typename27.C: New test.
> > ---
> >  gcc/cp/decl.cc                             |  9 ++++++++-
> >  gcc/cp/pt.cc                               |  9 ++++++++-
> >  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
> >  3 files changed, 35 insertions(+), 2 deletions(-)
> >  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> >
> > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > index 5369714f9b3..a0a20c5accc 100644
> > --- a/gcc/cp/decl.cc
> > +++ b/gcc/cp/decl.cc
> > @@ -4307,7 +4307,14 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
> >       lookup will stop when we hit a dependent base.  */
> >    if (!dependent_scope_p (context))
> >      {
> > -      bool want_type = (complain & tf_qualifying_scope);
> > +      /* As per [dcl.type.elab]/5 and [temp.res.general]/3, ignore non-types if
> > +      the tag corresponds to a class-key or 'enum' (or is scope_type), or if
> > +      this typename is followed by :: as per [basic.lookup.qual.general]/1.
> > +      TODO: If we'd set the scope_type tag accurately on all TYPENAME_TYPEs
> > +      that are followed by :: then we wouldn't need the tf_qualifying_scope
> > +      flag.  */
> > +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> > +     || (complain & tf_qualifying_scope);
>
> Here's v2 which just slightly improves this comment.  I reckon [basic.lookup.elab]
> is a better reference than [dcl.type.elab]/5 for justifying why the
> lookup should be type-only for class-key and 'enum' TYPENAME_TYPEs.
>
> -- >8 --
>
>         PR c++/109420
>
> gcc/cp/ChangeLog:
>
>         * decl.cc (make_typename_type): Also ignore non-types during the
>         lookup if tag_type corresponds to an elaborated-type-specifier.
>         * pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
>         enum_type as tag_type to make_typename_type as appropriate
>         instead of always passing typename_type.
>
> gcc/testsuite/ChangeLog:
>
>         * g++.dg/template/typename27.C: New test.
> ---
>  gcc/cp/decl.cc                             | 12 +++++++++++-
>  gcc/cp/pt.cc                               |  9 ++++++++-
>  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
>  3 files changed, 38 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
>
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 5369714f9b3..772c059dc2c 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -4307,7 +4307,17 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
>       lookup will stop when we hit a dependent base.  */
>    if (!dependent_scope_p (context))
>      {
> -      bool want_type = (complain & tf_qualifying_scope);
> +      /* We generally don't ignore non-types during TYPENAME_TYPE lookup
> +        (as per [temp.res.general]/3), unless
> +          - the tag corresponds to a class-key or 'enum' so
> +            [basic.lookup.elab] applies, or
> +          - the tag corresponds to scope_type or tf_qualifying_scope is
> +            set so [basic.lookup.qual]/1 applies.
> +        TODO: If we'd set/track the scope_type tag thoroughly on all
> +        TYPENAME_TYPEs that are followed by :: then we wouldn't need the
> +        tf_qualifying_scope flag.  */
> +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> +       || (complain & tf_qualifying_scope);
>        t = lookup_member (context, name, /*protect=*/2, want_type, complain);
>      }
>    else
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 821e0035c08..09559c88f29 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -16580,9 +16580,16 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>               return error_mark_node;
>           }
>
> +       /* FIXME: TYPENAME_IS_CLASS_P conflates 'union' vs 'struct' vs 'class'
> +          tags.  TYPENAME_TYPE should probably remember the exact tag that
> +          was written.  */

Yes I had a patch for that but I submitted during stage 4 of GCC 12
and never updated again during stage 1 of GCC 13. I hope to submit it
again with updated changes post this patch.

Thanks,
Andrew


> +       enum tag_types tag
> +         = TYPENAME_IS_CLASS_P (t) ? class_type
> +         : TYPENAME_IS_ENUM_P (t) ? enum_type
> +         : typename_type;
>         tsubst_flags_t tcomplain = complain | tf_keep_type_decl;
>         tcomplain |= tst_ok_flag | qualifying_scope_flag;
> -       f = make_typename_type (ctx, f, typename_type, tcomplain);
> +       f = make_typename_type (ctx, f, tag, tcomplain);
>         if (f == error_mark_node)
>           return f;
>         if (TREE_CODE (f) == TYPE_DECL)
> diff --git a/gcc/testsuite/g++.dg/template/typename27.C b/gcc/testsuite/g++.dg/template/typename27.C
> new file mode 100644
> index 00000000000..61b3efd998e
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/typename27.C
> @@ -0,0 +1,19 @@
> +// PR c++/109420
> +
> +struct A {
> +  struct X { };
> +  int X;
> +};
> +
> +struct B {
> +  enum E { };
> +  enum F { E };
> +};
> +
> +template<class T, class U>
> +void f() {
> +  struct T::X x; // OK, lookup ignores the data member 'int A::X'
> +  enum U::E e;   // OK, lookup ignores the enumerator 'B::F::E'
> +}
> +
> +template void f<A, B>();
> --
> 2.40.0.153.g6369acd968
>

Re: [PATCH] c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

[Jason Merrill]

On 4/5/23 13:31, Patrick Palka wrote:
> On Wed, 5 Apr 2023, Patrick Palka wrote:
> 
>> r13-6098-g46711ff8e60d64 made make_typename_type no longer ignore
>> non-types during the lookup, unless the TYPENAME_TYPE in question was
>> followed by the :: scope resolution operator.  But there is another
>> exception to this rule: we need to ignore non-types during the lookup
>> also if the TYPENAME_TYPE was named with a tag other than 'typename',
>> such as 'struct' or 'enum', as per [dcl.type.elab]/5.
>>
>> This patch implements this additional exception.  It occurred to me that
>> the tf_qualifying_scope flag is probably unnecessary if we'd use the
>> scope_type tag more thoroughly, but that requires parser changes that
>> are probably too risky at this stage.  (I'm working on addressing the
>> FIXME/TODOs here for GCC 14.)
>>
>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
>> trunk?
>>
>> 	PR c++/109420
>>
>> gcc/cp/ChangeLog:
>>
>> 	* decl.cc (make_typename_type): Also ignore non-types during
>> 	the lookup if tag_type is something other than none_type or
>> 	typename_type.
>> 	* pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
>> 	enum_type as tag_type to make_typename_type as appropriate
>> 	instead of always passing typename_type.
>>
>> gcc/testsuite/ChangeLog:
>>
>> 	* g++.dg/template/typename27.C: New test.
>> ---
>>   gcc/cp/decl.cc                             |  9 ++++++++-
>>   gcc/cp/pt.cc                               |  9 ++++++++-
>>   gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
>>   3 files changed, 35 insertions(+), 2 deletions(-)
>>   create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
>>
>> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
>> index 5369714f9b3..a0a20c5accc 100644
>> --- a/gcc/cp/decl.cc
>> +++ b/gcc/cp/decl.cc
>> @@ -4307,7 +4307,14 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
>>        lookup will stop when we hit a dependent base.  */
>>     if (!dependent_scope_p (context))
>>       {
>> -      bool want_type = (complain & tf_qualifying_scope);
>> +      /* As per [dcl.type.elab]/5 and [temp.res.general]/3, ignore non-types if
>> +	 the tag corresponds to a class-key or 'enum' (or is scope_type), or if
>> +	 this typename is followed by :: as per [basic.lookup.qual.general]/1.
>> +	 TODO: If we'd set the scope_type tag accurately on all TYPENAME_TYPEs
>> +	 that are followed by :: then we wouldn't need the tf_qualifying_scope
>> +	 flag.  */
>> +      bool want_type = (tag_type != none_type && tag_type != typename_type)
>> +	|| (complain & tf_qualifying_scope);
> 
> Here's v2 which just slightly improves this comment.  I reckon [basic.lookup.elab]
> is a better reference than [dcl.type.elab]/5 for justifying why the
> lookup should be type-only for class-key and 'enum' TYPENAME_TYPEs.

OK, thanks.

> -- >8 --
> 
> 	PR c++/109420
> 
> gcc/cp/ChangeLog:
> 
> 	* decl.cc (make_typename_type): Also ignore non-types during the
> 	lookup if tag_type corresponds to an elaborated-type-specifier.
> 	* pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> 	enum_type as tag_type to make_typename_type as appropriate
> 	instead of always passing typename_type.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/template/typename27.C: New test.
> ---
>   gcc/cp/decl.cc                             | 12 +++++++++++-
>   gcc/cp/pt.cc                               |  9 ++++++++-
>   gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
>   3 files changed, 38 insertions(+), 2 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> 
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 5369714f9b3..772c059dc2c 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -4307,7 +4307,17 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
>        lookup will stop when we hit a dependent base.  */
>     if (!dependent_scope_p (context))
>       {
> -      bool want_type = (complain & tf_qualifying_scope);
> +      /* We generally don't ignore non-types during TYPENAME_TYPE lookup
> +	 (as per [temp.res.general]/3), unless
> +	   - the tag corresponds to a class-key or 'enum' so
> +	     [basic.lookup.elab] applies, or
> +	   - the tag corresponds to scope_type or tf_qualifying_scope is
> +	     set so [basic.lookup.qual]/1 applies.
> +	 TODO: If we'd set/track the scope_type tag thoroughly on all
> +	 TYPENAME_TYPEs that are followed by :: then we wouldn't need the
> +	 tf_qualifying_scope flag.  */
> +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> +	|| (complain & tf_qualifying_scope);
>         t = lookup_member (context, name, /*protect=*/2, want_type, complain);
>       }
>     else
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 821e0035c08..09559c88f29 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -16580,9 +16580,16 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   	      return error_mark_node;
>   	  }
>   
> +	/* FIXME: TYPENAME_IS_CLASS_P conflates 'union' vs 'struct' vs 'class'
> +	   tags.  TYPENAME_TYPE should probably remember the exact tag that
> +	   was written.  */
> +	enum tag_types tag
> +	  = TYPENAME_IS_CLASS_P (t) ? class_type
> +	  : TYPENAME_IS_ENUM_P (t) ? enum_type
> +	  : typename_type;
>   	tsubst_flags_t tcomplain = complain | tf_keep_type_decl;
>   	tcomplain |= tst_ok_flag | qualifying_scope_flag;
> -	f = make_typename_type (ctx, f, typename_type, tcomplain);
> +	f = make_typename_type (ctx, f, tag, tcomplain);
>   	if (f == error_mark_node)
>   	  return f;
>   	if (TREE_CODE (f) == TYPE_DECL)
> diff --git a/gcc/testsuite/g++.dg/template/typename27.C b/gcc/testsuite/g++.dg/template/typename27.C
> new file mode 100644
> index 00000000000..61b3efd998e
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/typename27.C
> @@ -0,0 +1,19 @@
> +// PR c++/109420
> +
> +struct A {
> +  struct X { };
> +  int X;
> +};
> +
> +struct B {
> +  enum E { };
> +  enum F { E };
> +};
> +
> +template<class T, class U>
> +void f() {
> +  struct T::X x; // OK, lookup ignores the data member 'int A::X'
> +  enum U::E e;   // OK, lookup ignores the enumerator 'B::F::E'
> +}
> +
> +template void f<A, B>();

Re: [PATCH] c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

[Patrick Palka]

On Wed, Apr 5, 2023 at 1:36 PM Andrew Pinski <pinskia@gmail.com> wrote:
>
> On Wed, Apr 5, 2023 at 10:32 AM Patrick Palka via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > On Wed, 5 Apr 2023, Patrick Palka wrote:
> >
> > > r13-6098-g46711ff8e60d64 made make_typename_type no longer ignore
> > > non-types during the lookup, unless the TYPENAME_TYPE in question was
> > > followed by the :: scope resolution operator.  But there is another
> > > exception to this rule: we need to ignore non-types during the lookup
> > > also if the TYPENAME_TYPE was named with a tag other than 'typename',
> > > such as 'struct' or 'enum', as per [dcl.type.elab]/5.
> > >
> > > This patch implements this additional exception.  It occurred to me that
> > > the tf_qualifying_scope flag is probably unnecessary if we'd use the
> > > scope_type tag more thoroughly, but that requires parser changes that
> > > are probably too risky at this stage.  (I'm working on addressing the
> > > FIXME/TODOs here for GCC 14.)
> > >
> > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > > trunk?
> > >
> > >       PR c++/109420
> > >
> > > gcc/cp/ChangeLog:
> > >
> > >       * decl.cc (make_typename_type): Also ignore non-types during
> > >       the lookup if tag_type is something other than none_type or
> > >       typename_type.
> > >       * pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> > >       enum_type as tag_type to make_typename_type as appropriate
> > >       instead of always passing typename_type.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > >       * g++.dg/template/typename27.C: New test.
> > > ---
> > >  gcc/cp/decl.cc                             |  9 ++++++++-
> > >  gcc/cp/pt.cc                               |  9 ++++++++-
> > >  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
> > >  3 files changed, 35 insertions(+), 2 deletions(-)
> > >  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> > >
> > > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > > index 5369714f9b3..a0a20c5accc 100644
> > > --- a/gcc/cp/decl.cc
> > > +++ b/gcc/cp/decl.cc
> > > @@ -4307,7 +4307,14 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
> > >       lookup will stop when we hit a dependent base.  */
> > >    if (!dependent_scope_p (context))
> > >      {
> > > -      bool want_type = (complain & tf_qualifying_scope);
> > > +      /* As per [dcl.type.elab]/5 and [temp.res.general]/3, ignore non-types if
> > > +      the tag corresponds to a class-key or 'enum' (or is scope_type), or if
> > > +      this typename is followed by :: as per [basic.lookup.qual.general]/1.
> > > +      TODO: If we'd set the scope_type tag accurately on all TYPENAME_TYPEs
> > > +      that are followed by :: then we wouldn't need the tf_qualifying_scope
> > > +      flag.  */
> > > +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> > > +     || (complain & tf_qualifying_scope);
> >
> > Here's v2 which just slightly improves this comment.  I reckon [basic.lookup.elab]
> > is a better reference than [dcl.type.elab]/5 for justifying why the
> > lookup should be type-only for class-key and 'enum' TYPENAME_TYPEs.
> >
> > -- >8 --
> >
> >         PR c++/109420
> >
> > gcc/cp/ChangeLog:
> >
> >         * decl.cc (make_typename_type): Also ignore non-types during the
> >         lookup if tag_type corresponds to an elaborated-type-specifier.
> >         * pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> >         enum_type as tag_type to make_typename_type as appropriate
> >         instead of always passing typename_type.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * g++.dg/template/typename27.C: New test.
> > ---
> >  gcc/cp/decl.cc                             | 12 +++++++++++-
> >  gcc/cp/pt.cc                               |  9 ++++++++-
> >  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
> >  3 files changed, 38 insertions(+), 2 deletions(-)
> >  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> >
> > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > index 5369714f9b3..772c059dc2c 100644
> > --- a/gcc/cp/decl.cc
> > +++ b/gcc/cp/decl.cc
> > @@ -4307,7 +4307,17 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
> >       lookup will stop when we hit a dependent base.  */
> >    if (!dependent_scope_p (context))
> >      {
> > -      bool want_type = (complain & tf_qualifying_scope);
> > +      /* We generally don't ignore non-types during TYPENAME_TYPE lookup
> > +        (as per [temp.res.general]/3), unless
> > +          - the tag corresponds to a class-key or 'enum' so
> > +            [basic.lookup.elab] applies, or
> > +          - the tag corresponds to scope_type or tf_qualifying_scope is
> > +            set so [basic.lookup.qual]/1 applies.
> > +        TODO: If we'd set/track the scope_type tag thoroughly on all
> > +        TYPENAME_TYPEs that are followed by :: then we wouldn't need the
> > +        tf_qualifying_scope flag.  */
> > +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> > +       || (complain & tf_qualifying_scope);
> >        t = lookup_member (context, name, /*protect=*/2, want_type, complain);
> >      }
> >    else
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 821e0035c08..09559c88f29 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -16580,9 +16580,16 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> >               return error_mark_node;
> >           }
> >
> > +       /* FIXME: TYPENAME_IS_CLASS_P conflates 'union' vs 'struct' vs 'class'
> > +          tags.  TYPENAME_TYPE should probably remember the exact tag that
> > +          was written.  */
>
> Yes I had a patch for that but I submitted during stage 4 of GCC 12
> and never updated again during stage 1 of GCC 13. I hope to submit it
> again with updated changes post this patch.

That'd be great.  We could encode all possible tags using three
adjacent TREE_LANG_FLAG bits I think (so just one more bit than what
TYPENAME_TYPE currently uses).

>
> Thanks,
> Andrew
>
>
> > +       enum tag_types tag
> > +         = TYPENAME_IS_CLASS_P (t) ? class_type
> > +         : TYPENAME_IS_ENUM_P (t) ? enum_type
> > +         : typename_type;
> >         tsubst_flags_t tcomplain = complain | tf_keep_type_decl;
> >         tcomplain |= tst_ok_flag | qualifying_scope_flag;
> > -       f = make_typename_type (ctx, f, typename_type, tcomplain);
> > +       f = make_typename_type (ctx, f, tag, tcomplain);
> >         if (f == error_mark_node)
> >           return f;
> >         if (TREE_CODE (f) == TYPE_DECL)
> > diff --git a/gcc/testsuite/g++.dg/template/typename27.C b/gcc/testsuite/g++.dg/template/typename27.C
> > new file mode 100644
> > index 00000000000..61b3efd998e
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/template/typename27.C
> > @@ -0,0 +1,19 @@
> > +// PR c++/109420
> > +
> > +struct A {
> > +  struct X { };
> > +  int X;
> > +};
> > +
> > +struct B {
> > +  enum E { };
> > +  enum F { E };
> > +};
> > +
> > +template<class T, class U>
> > +void f() {
> > +  struct T::X x; // OK, lookup ignores the data member 'int A::X'
> > +  enum U::E e;   // OK, lookup ignores the enumerator 'B::F::E'
> > +}
> > +
> > +template void f<A, B>();
> > --
> > 2.40.0.153.g6369acd968
> >
>

Re: [PATCH] c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

[Patrick Palka]

[-- Attachment #1: Type: text/plain, Size: 7307 bytes --]

Hey Andrew,

On Wed, 5 Apr 2023, Andrew Pinski wrote:

> On Wed, Apr 5, 2023 at 10:32 AM Patrick Palka via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > On Wed, 5 Apr 2023, Patrick Palka wrote:
> >
> > > r13-6098-g46711ff8e60d64 made make_typename_type no longer ignore
> > > non-types during the lookup, unless the TYPENAME_TYPE in question was
> > > followed by the :: scope resolution operator.  But there is another
> > > exception to this rule: we need to ignore non-types during the lookup
> > > also if the TYPENAME_TYPE was named with a tag other than 'typename',
> > > such as 'struct' or 'enum', as per [dcl.type.elab]/5.
> > >
> > > This patch implements this additional exception.  It occurred to me that
> > > the tf_qualifying_scope flag is probably unnecessary if we'd use the
> > > scope_type tag more thoroughly, but that requires parser changes that
> > > are probably too risky at this stage.  (I'm working on addressing the
> > > FIXME/TODOs here for GCC 14.)
> > >
> > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > > trunk?
> > >
> > >       PR c++/109420
> > >
> > > gcc/cp/ChangeLog:
> > >
> > >       * decl.cc (make_typename_type): Also ignore non-types during
> > >       the lookup if tag_type is something other than none_type or
> > >       typename_type.
> > >       * pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> > >       enum_type as tag_type to make_typename_type as appropriate
> > >       instead of always passing typename_type.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > >       * g++.dg/template/typename27.C: New test.
> > > ---
> > >  gcc/cp/decl.cc                             |  9 ++++++++-
> > >  gcc/cp/pt.cc                               |  9 ++++++++-
> > >  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
> > >  3 files changed, 35 insertions(+), 2 deletions(-)
> > >  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> > >
> > > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > > index 5369714f9b3..a0a20c5accc 100644
> > > --- a/gcc/cp/decl.cc
> > > +++ b/gcc/cp/decl.cc
> > > @@ -4307,7 +4307,14 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
> > >       lookup will stop when we hit a dependent base.  */
> > >    if (!dependent_scope_p (context))
> > >      {
> > > -      bool want_type = (complain & tf_qualifying_scope);
> > > +      /* As per [dcl.type.elab]/5 and [temp.res.general]/3, ignore non-types if
> > > +      the tag corresponds to a class-key or 'enum' (or is scope_type), or if
> > > +      this typename is followed by :: as per [basic.lookup.qual.general]/1.
> > > +      TODO: If we'd set the scope_type tag accurately on all TYPENAME_TYPEs
> > > +      that are followed by :: then we wouldn't need the tf_qualifying_scope
> > > +      flag.  */
> > > +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> > > +     || (complain & tf_qualifying_scope);
> >
> > Here's v2 which just slightly improves this comment.  I reckon [basic.lookup.elab]
> > is a better reference than [dcl.type.elab]/5 for justifying why the
> > lookup should be type-only for class-key and 'enum' TYPENAME_TYPEs.
> >
> > -- >8 --
> >
> >         PR c++/109420
> >
> > gcc/cp/ChangeLog:
> >
> >         * decl.cc (make_typename_type): Also ignore non-types during the
> >         lookup if tag_type corresponds to an elaborated-type-specifier.
> >         * pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> >         enum_type as tag_type to make_typename_type as appropriate
> >         instead of always passing typename_type.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * g++.dg/template/typename27.C: New test.
> > ---
> >  gcc/cp/decl.cc                             | 12 +++++++++++-
> >  gcc/cp/pt.cc                               |  9 ++++++++-
> >  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
> >  3 files changed, 38 insertions(+), 2 deletions(-)
> >  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> >
> > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > index 5369714f9b3..772c059dc2c 100644
> > --- a/gcc/cp/decl.cc
> > +++ b/gcc/cp/decl.cc
> > @@ -4307,7 +4307,17 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
> >       lookup will stop when we hit a dependent base.  */
> >    if (!dependent_scope_p (context))
> >      {
> > -      bool want_type = (complain & tf_qualifying_scope);
> > +      /* We generally don't ignore non-types during TYPENAME_TYPE lookup
> > +        (as per [temp.res.general]/3), unless
> > +          - the tag corresponds to a class-key or 'enum' so
> > +            [basic.lookup.elab] applies, or
> > +          - the tag corresponds to scope_type or tf_qualifying_scope is
> > +            set so [basic.lookup.qual]/1 applies.
> > +        TODO: If we'd set/track the scope_type tag thoroughly on all
> > +        TYPENAME_TYPEs that are followed by :: then we wouldn't need the
> > +        tf_qualifying_scope flag.  */
> > +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> > +       || (complain & tf_qualifying_scope);
> >        t = lookup_member (context, name, /*protect=*/2, want_type, complain);
> >      }
> >    else
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 821e0035c08..09559c88f29 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -16580,9 +16580,16 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> >               return error_mark_node;
> >           }
> >
> > +       /* FIXME: TYPENAME_IS_CLASS_P conflates 'union' vs 'struct' vs 'class'
> > +          tags.  TYPENAME_TYPE should probably remember the exact tag that
> > +          was written.  */
> 
> Yes I had a patch for that but I submitted during stage 4 of GCC 12
> and never updated again during stage 1 of GCC 13. I hope to submit it
> again with updated changes post this patch.

Do you still plan on submitting a patch for this?  It would be great to
fix this for GCC 15 :)

> 
> Thanks,
> Andrew
> 
> 
> > +       enum tag_types tag
> > +         = TYPENAME_IS_CLASS_P (t) ? class_type
> > +         : TYPENAME_IS_ENUM_P (t) ? enum_type
> > +         : typename_type;
> >         tsubst_flags_t tcomplain = complain | tf_keep_type_decl;
> >         tcomplain |= tst_ok_flag | qualifying_scope_flag;
> > -       f = make_typename_type (ctx, f, typename_type, tcomplain);
> > +       f = make_typename_type (ctx, f, tag, tcomplain);
> >         if (f == error_mark_node)
> >           return f;
> >         if (TREE_CODE (f) == TYPE_DECL)
> > diff --git a/gcc/testsuite/g++.dg/template/typename27.C b/gcc/testsuite/g++.dg/template/typename27.C
> > new file mode 100644
> > index 00000000000..61b3efd998e
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/template/typename27.C
> > @@ -0,0 +1,19 @@
> > +// PR c++/109420
> > +
> > +struct A {
> > +  struct X { };
> > +  int X;
> > +};
> > +
> > +struct B {
> > +  enum E { };
> > +  enum F { E };
> > +};
> > +
> > +template<class T, class U>
> > +void f() {
> > +  struct T::X x; // OK, lookup ignores the data member 'int A::X'
> > +  enum U::E e;   // OK, lookup ignores the enumerator 'B::F::E'
> > +}
> > +
> > +template void f<A, B>();
> > --
> > 2.40.0.153.g6369acd968
> >
> 
> 

Re: [PATCH] c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

[Andrew Pinski]

On Fri, May 3, 2024 at 8:08 AM Patrick Palka <ppalka@redhat.com> wrote:
>
> Hey Andrew,
>
> On Wed, 5 Apr 2023, Andrew Pinski wrote:
>
> > On Wed, Apr 5, 2023 at 10:32 AM Patrick Palka via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > On Wed, 5 Apr 2023, Patrick Palka wrote:
> > >
> > > > r13-6098-g46711ff8e60d64 made make_typename_type no longer ignore
> > > > non-types during the lookup, unless the TYPENAME_TYPE in question was
> > > > followed by the :: scope resolution operator.  But there is another
> > > > exception to this rule: we need to ignore non-types during the lookup
> > > > also if the TYPENAME_TYPE was named with a tag other than 'typename',
> > > > such as 'struct' or 'enum', as per [dcl.type.elab]/5.
> > > >
> > > > This patch implements this additional exception.  It occurred to me that
> > > > the tf_qualifying_scope flag is probably unnecessary if we'd use the
> > > > scope_type tag more thoroughly, but that requires parser changes that
> > > > are probably too risky at this stage.  (I'm working on addressing the
> > > > FIXME/TODOs here for GCC 14.)
> > > >
> > > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > > > trunk?
> > > >
> > > >       PR c++/109420
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > >       * decl.cc (make_typename_type): Also ignore non-types during
> > > >       the lookup if tag_type is something other than none_type or
> > > >       typename_type.
> > > >       * pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> > > >       enum_type as tag_type to make_typename_type as appropriate
> > > >       instead of always passing typename_type.
> > > >
> > > > gcc/testsuite/ChangeLog:
> > > >
> > > >       * g++.dg/template/typename27.C: New test.
> > > > ---
> > > >  gcc/cp/decl.cc                             |  9 ++++++++-
> > > >  gcc/cp/pt.cc                               |  9 ++++++++-
> > > >  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
> > > >  3 files changed, 35 insertions(+), 2 deletions(-)
> > > >  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> > > >
> > > > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > > > index 5369714f9b3..a0a20c5accc 100644
> > > > --- a/gcc/cp/decl.cc
> > > > +++ b/gcc/cp/decl.cc
> > > > @@ -4307,7 +4307,14 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
> > > >       lookup will stop when we hit a dependent base.  */
> > > >    if (!dependent_scope_p (context))
> > > >      {
> > > > -      bool want_type = (complain & tf_qualifying_scope);
> > > > +      /* As per [dcl.type.elab]/5 and [temp.res.general]/3, ignore non-types if
> > > > +      the tag corresponds to a class-key or 'enum' (or is scope_type), or if
> > > > +      this typename is followed by :: as per [basic.lookup.qual.general]/1.
> > > > +      TODO: If we'd set the scope_type tag accurately on all TYPENAME_TYPEs
> > > > +      that are followed by :: then we wouldn't need the tf_qualifying_scope
> > > > +      flag.  */
> > > > +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> > > > +     || (complain & tf_qualifying_scope);
> > >
> > > Here's v2 which just slightly improves this comment.  I reckon [basic.lookup.elab]
> > > is a better reference than [dcl.type.elab]/5 for justifying why the
> > > lookup should be type-only for class-key and 'enum' TYPENAME_TYPEs.
> > >
> > > -- >8 --
> > >
> > >         PR c++/109420
> > >
> > > gcc/cp/ChangeLog:
> > >
> > >         * decl.cc (make_typename_type): Also ignore non-types during the
> > >         lookup if tag_type corresponds to an elaborated-type-specifier.
> > >         * pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
> > >         enum_type as tag_type to make_typename_type as appropriate
> > >         instead of always passing typename_type.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > >         * g++.dg/template/typename27.C: New test.
> > > ---
> > >  gcc/cp/decl.cc                             | 12 +++++++++++-
> > >  gcc/cp/pt.cc                               |  9 ++++++++-
> > >  gcc/testsuite/g++.dg/template/typename27.C | 19 +++++++++++++++++++
> > >  3 files changed, 38 insertions(+), 2 deletions(-)
> > >  create mode 100644 gcc/testsuite/g++.dg/template/typename27.C
> > >
> > > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > > index 5369714f9b3..772c059dc2c 100644
> > > --- a/gcc/cp/decl.cc
> > > +++ b/gcc/cp/decl.cc
> > > @@ -4307,7 +4307,17 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
> > >       lookup will stop when we hit a dependent base.  */
> > >    if (!dependent_scope_p (context))
> > >      {
> > > -      bool want_type = (complain & tf_qualifying_scope);
> > > +      /* We generally don't ignore non-types during TYPENAME_TYPE lookup
> > > +        (as per [temp.res.general]/3), unless
> > > +          - the tag corresponds to a class-key or 'enum' so
> > > +            [basic.lookup.elab] applies, or
> > > +          - the tag corresponds to scope_type or tf_qualifying_scope is
> > > +            set so [basic.lookup.qual]/1 applies.
> > > +        TODO: If we'd set/track the scope_type tag thoroughly on all
> > > +        TYPENAME_TYPEs that are followed by :: then we wouldn't need the
> > > +        tf_qualifying_scope flag.  */
> > > +      bool want_type = (tag_type != none_type && tag_type != typename_type)
> > > +       || (complain & tf_qualifying_scope);
> > >        t = lookup_member (context, name, /*protect=*/2, want_type, complain);
> > >      }
> > >    else
> > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > > index 821e0035c08..09559c88f29 100644
> > > --- a/gcc/cp/pt.cc
> > > +++ b/gcc/cp/pt.cc
> > > @@ -16580,9 +16580,16 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> > >               return error_mark_node;
> > >           }
> > >
> > > +       /* FIXME: TYPENAME_IS_CLASS_P conflates 'union' vs 'struct' vs 'class'
> > > +          tags.  TYPENAME_TYPE should probably remember the exact tag that
> > > +          was written.  */
> >
> > Yes I had a patch for that but I submitted during stage 4 of GCC 12
> > and never updated again during stage 1 of GCC 13. I hope to submit it
> > again with updated changes post this patch.
>
> Do you still plan on submitting a patch for this?  It would be great to
> fix this for GCC 15 :)

I think I will be getting back to that patch the first week of June
and submitting an updated version based on the previous review. I have
a few other patches I am working on before I can start working on that
one.

Thanks,
Andrew

>
> >
> > Thanks,
> > Andrew
> >
> >
> > > +       enum tag_types tag
> > > +         = TYPENAME_IS_CLASS_P (t) ? class_type
> > > +         : TYPENAME_IS_ENUM_P (t) ? enum_type
> > > +         : typename_type;
> > >         tsubst_flags_t tcomplain = complain | tf_keep_type_decl;
> > >         tcomplain |= tst_ok_flag | qualifying_scope_flag;
> > > -       f = make_typename_type (ctx, f, typename_type, tcomplain);
> > > +       f = make_typename_type (ctx, f, tag, tcomplain);
> > >         if (f == error_mark_node)
> > >           return f;
> > >         if (TREE_CODE (f) == TYPE_DECL)
> > > diff --git a/gcc/testsuite/g++.dg/template/typename27.C b/gcc/testsuite/g++.dg/template/typename27.C
> > > new file mode 100644
> > > index 00000000000..61b3efd998e
> > > --- /dev/null
> > > +++ b/gcc/testsuite/g++.dg/template/typename27.C
> > > @@ -0,0 +1,19 @@
> > > +// PR c++/109420
> > > +
> > > +struct A {
> > > +  struct X { };
> > > +  int X;
> > > +};
> > > +
> > > +struct B {
> > > +  enum E { };
> > > +  enum F { E };
> > > +};
> > > +
> > > +template<class T, class U>
> > > +void f() {
> > > +  struct T::X x; // OK, lookup ignores the data member 'int A::X'
> > > +  enum U::E e;   // OK, lookup ignores the enumerator 'B::F::E'
> > > +}
> > > +
> > > +template void f<A, B>();
> > > --
> > > 2.40.0.153.g6369acd968
> > >
> >
> >