On Wed, 15 Feb 2023, Jason Merrill wrote:
> On 2/15/23 09:21, Patrick Palka wrote:
> > On Tue, 14 Feb 2023, Jason Merrill wrote:
> >
> > > On 2/13/23 09:23, Patrick Palka wrote:
> > > > [N.B. this is a corrected version of
> > > > https://gcc.gnu.org/pipermail/gcc-patches/2022-November/607443.html ]
> > > >
> > > > This patch factors out the TYPENAME_TYPE case of tsubst into a separate
> > > > function tsubst_typename_type. It also factors out the two tsubst flags
> > > > controlling TYPENAME_TYPE substitution, tf_keep_type_decl and tf_tst_ok,
> > > > into distinct boolean parameters of this new function (and of
> > > > make_typename_type). Consequently, callers which used to pass tf_tst_ok
> > > > to tsubst now instead must directly call tsubst_typename_type when
> > > > appropriate.
> > >
> > > Hmm, I don't love how that turns 4 lines into 8 more complex lines in each
> > > caller. And the previous approach of saying "a CTAD placeholder is OK"
> > > seem
> > > like better abstraction than repeating the specific TYPENAME_TYPE handling
> > > in
> > > each place.
> >
> > Ah yeah, I see what you mean. I was thinking since tf_tst_ok is
> > specific to TYPENAME_TYPE handling and isn't propagated (i.e. it only
> > affects top-level TYPENAME_TYPEs), it seemed cleaner to encode the flag
> > as a bool parameter "template_ok" of tsubst_typename_type instead of as
> > a global tsubst_flag that gets propagated freely.
> >
> > >
> > > > In a subsequent patch we'll add another flag to
> > > > tsubst_typename_type controlling whether we want to ignore non-types
> > > > during the qualified lookup.
> >
> > As mentioned above, the second patch in this series would just add
> > another flag "type_only" alongside "template_ok", since this flag will
> > also only affects top-level TYPENAME_TYPEs and doesn't need to propagate
> > like tsubst_flags.
> >
> > Except, it turns it, this new flag _does_ need to propagate, namely when
> > expanding a variadic using:
> >
> > using typename Ts::type::m...; // from typename25a.C below
> >
> > Here we have a USING_DECL whose USING_DECL_SCOPE is a
> > TYPE_PACK_EXPANSION over TYPENAME_TYPE. In order to correctly
> > substitute this TYPENAME_TYPE, the USING_DECL case of tsubst_decl needs
> > to pass an appropriate tsubst_flag to tsubst_pack_expansion to be
> > propagated to tsubst (to be propagated to make_typename_type).
> >
> > So in light of this case it seems adding a new tsubst_flag is the
> > way to go, which means we can avoid this refactoring patch entirely.
> >
> > Like so? Bootstrapped and regtested on x86_64-pc-linux-gnu.
>
> OK, though I still wonder about adding a tsubst_scope function that would add
> the tf_qualifying_scope.
Hmm, but we need to add tf_qualifying_scope to two tsubst_copy calls,
one tsubst call and one tsubst_aggr_type call (with entering_scope=true).
Would tsubst_scope call tsubst, tsubst_copy or tsubst_aggr_type?
>
> > -- >8 --
> >
> > Subject: [PATCH] c++: TYPENAME_TYPE lookup ignoring non-types [PR107773]
> >
> > Currently when resolving a TYPENAME_TYPE for 'typename T::m' via
> > make_typename_type, we consider only type bindings of 'm' and ignore
> > non-type ones. But [temp.res.general]/3 says, in a note, "the usual
> > qualified name lookup ([basic.lookup.qual]) applies even in the presence
> > of 'typename'", and qualified name lookup doesn't discriminate between
> > type and non-type bindings. So when resolving such a TYPENAME_TYPE
> > we want the lookup to consider all bindings.
> >
> > An exception is when we have a TYPENAME_TYPE corresponding to the
> > qualifying scope of the :: scope resolution operator, such as
> > 'T::type' in 'typename T::type::m'. In that case, [basic.lookup.qual]/1
> > applies, and lookup for such a TYPENAME_TYPE must ignore non-type bindings.
> > So in order to correctly handle all cases, make_typename_type needs an
> > additional flag controlling whether lookup should ignore non-types or not.
> >
> > To that end this patch adds a new tsubst flag tf_qualifying_scope to
> > communicate to make_typename_type whether we want to ignore non-type
> > bindings during the lookup (by default we don't want to ignore them).
> > In contexts where we do want to ignore non-types (when substituting
> > into the scope of TYPENAME_TYPE, SCOPE_REF or USING_DECL) we simply
> > pass tf_qualifying_scope to the relevant tsubst / tsubst_copy call.
> > This flag is intended to apply only to top-level TYPENAME_TYPEs so
> > we must be careful to clear the flag to avoid propagating it during
> > substitution of sub-trees.
> >
> > PR c++/107773
> >
> > gcc/cp/ChangeLog:
> >
> > * cp-tree.h (enum tsubst_flags): New flag tf_qualifying_scope.
> > * decl.cc (make_typename_type): Use lookup_member instead of
> > lookup_field. If tf_qualifying_scope is set, pass want_type=true
> > instead of =false to lookup_member. Generalize format specifier
> > in diagnostic to handle both type and non-type bindings.
> > * pt.cc (tsubst_aggr_type_1): Clear tf_qualifying_scope. Tidy
> > the function.
> > (tsubst_decl) <case USING_DECL>: Set tf_qualifying_scope when
> > substituting USING_DECL_SCOPE.
> > (tsubst): Clear tf_qualifying_scope right away and remember if
> > it was set. Do the same for tf_tst_ok sooner.
> > <case TYPENAME_TYPE>: Set tf_qualifying_scope when substituting
> > TYPE_CONTEXT. Pass tf_qualifying_scope to make_typename_type
> > if it was set.
> > (tsubst_qualified_id): Set tf_qualifying_scope when substituting
> > the scope.
> > (tsubst_copy): Clear tf_qualifying_scope and remember if it was
> > set.
> > <case SCOPE_REF>: Set tf_qualifying_scope when substituting the
> > scope.
> > <case *_TYPE>: Pass tf_qualifying_scope to tsubst if it was set.
> > * search.cc (lookup_member): Document default argument.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/template/typename24.C: New test.
> > * g++.dg/template/typename25.C: New test.
> > * g++.dg/template/typename25a.C: New test.
> > * g++.dg/template/typename26.C: New test.
> > ---
> > gcc/cp/cp-tree.h | 3 ++
> > gcc/cp/decl.cc | 9 ++--
> > gcc/cp/pt.cc | 58 ++++++++++++---------
> > gcc/cp/search.cc | 2 +-
> > gcc/testsuite/g++.dg/template/typename24.C | 18 +++++++
> > gcc/testsuite/g++.dg/template/typename25.C | 33 ++++++++++++
> > gcc/testsuite/g++.dg/template/typename25a.C | 37 +++++++++++++
> > gcc/testsuite/g++.dg/template/typename26.C | 20 +++++++
> > 8 files changed, 150 insertions(+), 30 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/template/typename24.C
> > create mode 100644 gcc/testsuite/g++.dg/template/typename25.C
> > create mode 100644 gcc/testsuite/g++.dg/template/typename25a.C
> > create mode 100644 gcc/testsuite/g++.dg/template/typename26.C
> >
> > diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> > index be8775ed0f8..891fcf521a8 100644
> > --- a/gcc/cp/cp-tree.h
> > +++ b/gcc/cp/cp-tree.h
> > @@ -5597,6 +5597,9 @@ enum tsubst_flags {
> > tf_tst_ok = 1 << 12, /* Allow a typename-specifier to name
> > a template (C++17 or later). */
> > tf_dguide = 1 << 13, /* Building a deduction guide from a
> > ctor. */
> > + tf_qualifying_scope = 1 << 14, /* Substituting the LHS of the ::
> > operator.
> > + Controls TYPENAME_TYPE resolution from
> > + make_typename_type. */
> > /* Convenient substitution flags combinations. */
> > tf_warning_or_error = tf_warning | tf_error
> > };
> > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> > index d606b31d7a7..2f6412d04e6 100644
> > --- a/gcc/cp/decl.cc
> > +++ b/gcc/cp/decl.cc
> > @@ -4305,9 +4305,10 @@ make_typename_type (tree context, tree name, enum
> > tag_types tag_type,
> > member of the current instantiation or a non-dependent base;
> > lookup will stop when we hit a dependent base. */
> > if (!dependent_scope_p (context))
> > - /* We should only set WANT_TYPE when we're a nested typename type.
> > - Then we can give better diagnostics if we find a non-type. */
> > - t = lookup_field (context, name, 2, /*want_type=*/true);
> > + {
> > + bool want_type = (complain & tf_qualifying_scope);
> > + t = lookup_member (context, name, /*protect=*/2, want_type,
> > complain);
> > + }
> > else
> > t = NULL_TREE;
> > @@ -4359,7 +4360,7 @@ make_typename_type (tree context, tree name, enum
> > tag_types tag_type,
> > else
> > {
> > if (complain & tf_error)
> > - error ("%<typename %T::%D%> names %q#T, which is not a type",
> > + error ("%<typename %T::%D%> names %q#D, which is not a type",
> > context, name, t);
> > return error_mark_node;
> > }
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index e89dbf47097..d11d540ab44 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -13919,8 +13919,7 @@ tsubst_aggr_type_1 (tree t,
> > {
> > if (TYPE_TEMPLATE_INFO (t) && uses_template_parms (t))
> > {
> > - tree argvec;
> > - tree r;
> > + complain &= ~tf_qualifying_scope;
> > /* Figure out what arguments are appropriate for the
> > type we are trying to find. For example, given:
> > @@ -13931,18 +13930,14 @@ tsubst_aggr_type_1 (tree t,
> > and supposing that we are instantiating f<int, double>,
> > then our ARGS will be {int, double}, but, when looking up
> > S we only want {double}. */
> > - argvec = tsubst_template_args (TYPE_TI_ARGS (t), args,
> > - complain, in_decl);
> > + tree argvec = tsubst_template_args (TYPE_TI_ARGS (t), args,
> > + complain, in_decl);
> > if (argvec == error_mark_node)
> > - r = error_mark_node;
> > - else
> > - {
> > - r = lookup_template_class (t, argvec, in_decl, NULL_TREE,
> > - entering_scope, complain);
> > - r = cp_build_qualified_type (r, cp_type_quals (t), complain);
> > - }
> > + return error_mark_node;
> > - return r;
> > + tree r = lookup_template_class (t, argvec, in_decl, NULL_TREE,
> > + entering_scope, complain);
> > + return cp_build_qualified_type (r, cp_type_quals (t), complain);
> > }
> > else
> > /* This is not a template type, so there's nothing to do. */
> > @@ -15003,11 +14998,15 @@ tsubst_decl (tree t, tree args, tsubst_flags_t
> > complain)
> > tree scope = USING_DECL_SCOPE (t);
> > if (PACK_EXPANSION_P (scope))
> > {
> > - scope = tsubst_pack_expansion (scope, args, complain, in_decl);
> > + scope = tsubst_pack_expansion (scope, args,
> > + complain | tf_qualifying_scope,
> > + in_decl);
> > variadic_p = true;
> > }
> > else
> > - scope = tsubst_copy (scope, args, complain, in_decl);
> > + scope = tsubst_copy (scope, args,
> > + complain | tf_qualifying_scope,
> > + in_decl);
> > tree name = DECL_NAME (t);
> > if (IDENTIFIER_CONV_OP_P (name)
> > @@ -15821,6 +15820,12 @@ tsubst (tree t, tree args, tsubst_flags_t complain,
> > tree in_decl)
> > || TREE_CODE (t) == TRANSLATION_UNIT_DECL)
> > return t;
> > + tsubst_flags_t tst_ok_flag = (complain & tf_tst_ok);
> > + complain &= ~tf_tst_ok;
> > +
> > + tsubst_flags_t qualifying_scope_flag = (complain & tf_qualifying_scope);
> > + complain &= ~tf_qualifying_scope;
> > +
> > if (DECL_P (t))
> > return tsubst_decl (t, args, complain);
> > @@ -15889,9 +15894,6 @@ tsubst (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > bool fndecl_type = (complain & tf_fndecl_type);
> > complain &= ~tf_fndecl_type;
> > - bool tst_ok = (complain & tf_tst_ok);
> > - complain &= ~tf_tst_ok;
> > -
> > if (type
> > && code != TYPENAME_TYPE
> > && code != TEMPLATE_TYPE_PARM
> > @@ -16428,7 +16430,9 @@ tsubst (tree t, tree args, tsubst_flags_t complain,
> > tree in_decl)
> > tree ctx = TYPE_CONTEXT (t);
> > if (TREE_CODE (ctx) == TYPE_PACK_EXPANSION)
> > {
> > - ctx = tsubst_pack_expansion (ctx, args, complain, in_decl);
> > + ctx = tsubst_pack_expansion (ctx, args,
> > + complain | tf_qualifying_scope,
> > + in_decl);
> > if (ctx == error_mark_node
> > || TREE_VEC_LENGTH (ctx) > 1)
> > return error_mark_node;
> > @@ -16442,8 +16446,9 @@ tsubst (tree t, tree args, tsubst_flags_t complain,
> > tree in_decl)
> > ctx = TREE_VEC_ELT (ctx, 0);
> > }
> > else
> > - ctx = tsubst_aggr_type (ctx, args, complain, in_decl,
> > - /*entering_scope=*/1);
> > + ctx = tsubst_aggr_type (ctx, args,
> > + complain | tf_qualifying_scope,
> > + in_decl, /*entering_scope=*/1);
> > if (ctx == error_mark_node)
> > return error_mark_node;
> > @@ -16473,8 +16478,7 @@ tsubst (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > }
> > tsubst_flags_t tcomplain = complain | tf_keep_type_decl;
> > - if (tst_ok)
> > - tcomplain |= tf_tst_ok;
> > + tcomplain |= tst_ok_flag | qualifying_scope_flag;
> > f = make_typename_type (ctx, f, typename_type, tcomplain);
> > if (f == error_mark_node)
> > return f;
> > @@ -16879,7 +16883,7 @@ tsubst_qualified_id (tree qualified_id, tree args,
> > scope = TREE_OPERAND (qualified_id, 0);
> > if (args)
> > {
> > - scope = tsubst (scope, args, complain, in_decl);
> > + scope = tsubst (scope, args, complain | tf_qualifying_scope,
> > in_decl);
> > expr = tsubst_copy (name, args, complain, in_decl);
> > }
> > else
> > @@ -17125,6 +17129,9 @@ tsubst_copy (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > if (t == NULL_TREE || t == error_mark_node || args == NULL_TREE)
> > return t;
> > + tsubst_flags_t qualifying_scope_flag = (complain &
> > tf_qualifying_scope);
> > + complain &= ~tf_qualifying_scope;
> > +
> > if (tree d = maybe_dependent_member_ref (t, args, complain, in_decl))
> > return d;
> > @@ -17598,7 +17605,8 @@ tsubst_copy (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > case SCOPE_REF:
> > {
> > - tree op0 = tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl);
> > + tree op0 = tsubst_copy (TREE_OPERAND (t, 0), args,
> > + complain | tf_qualifying_scope, in_decl);
> > tree op1 = tsubst_copy (TREE_OPERAND (t, 1), args, complain, in_decl);
> > return build_qualified_name (/*type=*/NULL_TREE, op0, op1,
> > QUALIFIED_NAME_IS_TEMPLATE (t));
> > @@ -17713,7 +17721,7 @@ tsubst_copy (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > case TYPEOF_TYPE:
> > case DECLTYPE_TYPE:
> > case TYPE_DECL:
> > - return tsubst (t, args, complain, in_decl);
> > + return tsubst (t, args, complain | qualifying_scope_flag, in_decl);
> > case USING_DECL:
> > t = DECL_NAME (t);
> > diff --git a/gcc/cp/search.cc b/gcc/cp/search.cc
> > index f3f19cafec6..e472a97679d 100644
> > --- a/gcc/cp/search.cc
> > +++ b/gcc/cp/search.cc
> > @@ -1109,7 +1109,7 @@ build_baselink (tree binfo, tree access_binfo, tree
> > functions, tree optype)
> > tree
> > lookup_member (tree xbasetype, tree name, int protect, bool want_type,
> > - tsubst_flags_t complain, access_failure_info *afi)
> > + tsubst_flags_t complain, access_failure_info *afi /* = NULL */)
> > {
> > tree rval, rval_binfo = NULL_TREE;
> > tree type = NULL_TREE, basetype_path = NULL_TREE;
> > diff --git a/gcc/testsuite/g++.dg/template/typename24.C
> > b/gcc/testsuite/g++.dg/template/typename24.C
> > new file mode 100644
> > index 00000000000..8b2b3718442
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/template/typename24.C
> > @@ -0,0 +1,18 @@
> > +// PR c++/107773
> > +// Verify lookup for a non-neste TYPENAME_TYPE correctly considers
> > +// non-types.
> > +
> > +struct a {
> > + typedef void get;
> > +};
> > +
> > +struct b : a {
> > + int get(int i) const;
> > +};
> > +
> > +template<class T>
> > +void f() {
> > + typedef typename T::get type; // { dg-error "'int b::get\\(int\\) const',
> > which is not a type" }
> > +}
> > +
> > +template void f<b>();
> > diff --git a/gcc/testsuite/g++.dg/template/typename25.C
> > b/gcc/testsuite/g++.dg/template/typename25.C
> > new file mode 100644
> > index 00000000000..04e48e11724
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/template/typename25.C
> > @@ -0,0 +1,33 @@
> > +// PR c++/107773
> > +// Verify lookup for TYPENAME_TYPE appearing to the left of the ::
> > +// scope resolution operator correctly ignores non-types.
> > +
> > +struct a {
> > + typedef void type;
> > +};
> > +
> > +struct c {
> > + struct b : a {
> > + typedef b self;
> > + static int m;
> > + };
> > + int b;
> > +};
> > +
> > +template<class T>
> > +void f() {
> > + // A TYPENAME_TYPE whose TYPE_CONTEXT is a nested TYPENAME_TYPE.
> > + typedef typename T::b::type type;
> > + // A SCOPE_REF whose first operand is a TYPENAME_TYPE.
> > + int m = T::b::m;
> > +}
> > +
> > +template void f<c>();
> > +
> > +template<class T>
> > +struct d : T::b::self {
> > + // A USING_DECL whose USING_DECL_SCOPE is a TYPENAME_TYPE.
> > + using typename T::b::type;
> > +};
> > +
> > +template struct d<c>;
> > diff --git a/gcc/testsuite/g++.dg/template/typename25a.C
> > b/gcc/testsuite/g++.dg/template/typename25a.C
> > new file mode 100644
> > index 00000000000..ecb34aada34
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/template/typename25a.C
> > @@ -0,0 +1,37 @@
> > +// PR c++/107773
> > +// A variadic version of typename25.C
> > +// { dg-do compile { target c++11 } }
> > +
> > +struct a {
> > + typedef void type;
> > +};
> > +
> > +struct c {
> > + struct b : a {
> > + typedef b self;
> > + static int m;
> > + };
> > + int b;
> > +};
> > +
> > +template<class...> void sink(...);
> > +
> > +template<class... Ts>
> > +void f() {
> > + // A TYPENAME_TYPE whose TYPE_CONTEXT is a nested TYPENAME_TYPE.
> > + sink<typename Ts::b::type...>();
> > + // A SCOPE_REF whose first operand is a TYPENAME_TYPE.
> > + sink(Ts::b::m...);
> > +}
> > +
> > +template void f<c>();
> > +
> > +template<class... Ts>
> > +struct d : Ts::b::self... {
> > +#if __cpp_variadic_using
> > + // A USING_DECL whose USING_DECL_SCOPE is a TYPENAME_TYPE.
> > + using typename Ts::b::type...;
> > +#endif
> > +};
> > +
> > +template struct d<c>;
> > diff --git a/gcc/testsuite/g++.dg/template/typename26.C
> > b/gcc/testsuite/g++.dg/template/typename26.C
> > new file mode 100644
> > index 00000000000..4e6b764a97b
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/template/typename26.C
> > @@ -0,0 +1,20 @@
> > +// Example 4 from [temp.res.general]/3.
> > +
> > +struct A {
> > + struct X { };
> > + int X;
> > +};
> > +struct B {
> > + struct X { };
> > +};
> > +template<class T> void f(T t) {
> > + typename T::X x; // { dg-error "'int A::X', which is not a type" }
> > +}
> > +void foo() {
> > + A a;
> > + B b;
> > + f(b); // OK, T::X refers to B::X
> > + // { dg-bogus "" "" { target *-*-* } .-1 }
> > + f(a); // error: T::X refers to the data member A::X not the struct A::X
> > + // { dg-message "required from here" "" { target *-*-* } .-1 }
> > +}
>
>
