On Mon, 28 Nov 2022, Patrick Palka wrote:
> [temp.res.general]/3 says, in a note, "the usual qualified name lookup
> ([basic.lookup.qual]) applies even in the presence of typename". Thus
> when resolving a TYPENAME_TYPE, it seems we shouldn't be looking past
> non-type members.
>
> This patch fixes this by passing want_type=false instead of =true during
> the member lookup from make_typename_type. An old nearby comment
> mentions that we want to continue to set want_type=true when resolving a
> nested typename type, but it appears that the nested case is handled by
> resolve_typename_type instead (which passes want_type=true appropriately).
Whoops, it seems this isn't true -- not all nested TYPENAME_TYPEs are
handled by resolve_typename_type, e.g. for T::b in
struct a {
struct b { typedef void get; };
int b;
};
template
void f() {
typedef typename T::b::get type;
}
template void f();
Passing want_type=false in make_typename_type causes us to incorrectly
reject the TYPENAME_TYPE for T::b here because qualified lookup now
finds the data member a::b instead of the nested class of the same name.
So it looks like we need a flag to control whether we're dealing with a
nested TYPENAME_TYPE or not and to pass want_type=true/false appropriately,
I'll poke more tomorrow.
>
> In passing, use lookup_member instead of lookup_field so that we give a
> better diagnostic when a member function is found, and generalize the T
> format specifier to D in the diagnostic.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?
>
> PR c++/107773
>
> gcc/cp/ChangeLog:
>
> * decl.cc (make_typename_type): Use lookup_member instead of
> lookup_field. Pass want_type=false instead of =true. Use D
> instead of T format specifier.
> * search.cc (lookup_member): Document default argument.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/template/typename24.C: New test.
> * g++.dg/template/typename25.C: New test.
> ---
> gcc/cp/decl.cc | 7 +++
> gcc/cp/search.cc | 2 +-
> gcc/testsuite/g++.dg/template/typename24.C | 16
> gcc/testsuite/g++.dg/template/typename25.C | 20
> 4 files changed, 40 insertions(+), 5 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/template/typename24.C
> create mode 100644 gcc/testsuite/g++.dg/template/typename25.C
>
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 238e72f90da..673e10801a6 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -4303,9 +4303,8 @@ 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);
> +t = lookup_member (context, name, /*protect=*/2, /*want_type=*/false,
> +complain);
>else
> t = NULL_TREE;
>
> @@ -4357,7 +4356,7 @@ make_typename_type (tree context, tree name, enum
> tag_types tag_type,
>else
> {
> if (complain & tf_error)
> - error ("% names %q#T, which is not a type",
> + error ("% names %q#D, which is not a type",
> context, name, t);
> return error_mark_node;
> }
> diff --git a/gcc/cp/search.cc b/gcc/cp/search.cc
> index 0dbb3be1ee7..e5848ebc620 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 000..4b1d5e5271b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/typename24.C
> @@ -0,0 +1,16 @@
> +// PR c++/107773
> +
> +struct a {
> + typedef void get;
> +};
> +
> +struct b : a {
> + int get(int i) const;
> +};
> +
> +template
> +void f() {
> + typedef typename T::get type; // { dg-error "'int b::get\\(int\\) const',
> which is not a type" }
> +}
> +
> +template void f();
> diff --git a/gcc/testsuite/g++.dg/template/typename25.C
> b/gcc/testsuite/g++.dg/template/typename25.C
> new file mode 100644
> index 000..4e6b764a97b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/typename25.C
> @@ -0,0 +1,20 @@
> +// Example 4 from [temp.res.general]/3.
> +
> +struct A {
> +