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. -- >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 } +} -- 2.39.2.422.gc867e4fa18