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 >