[PATCH] c++: substituting CONST_DECL_USING_P enumerator [PR103081]
Jason Merrill
jason@redhat.com
Fri Dec 2 19:37:08 GMT 2022
On 12/2/22 14:01, Patrick Palka wrote:
> We implement using enum at class scope by injecting clones of the enum's
> CONST_DECLs as fields of the class, for which CONST_DECL_USING_P is
> true, so that qualified lookup naturally finds the enumerators.
> Substitution into such a CONST_DECL currently ICEs however, because we
> assume the DECL_CONTEXT is always the ENUMERAL_TYPE (which has TYPE_VALUES)
> but in this case it's the RECORD_TYPE of the class scope (which has
> TYPE_FIELDS).
>
> Since these CONST_DECLs appear to always be non-dependent, this patch
> fixes this by shortcutting substitution for CONST_DECLs which have a
> non-dependent scope. This subsumes the existing (and seemingly dead)
> DECL_NAMESPACE_SCOPE_P early exit test and also benefits substitution
> into ordinary non-dependent CONST_DECLs.
>
> Bootstrapped and regtested on x86_64-pc-linu-xgnu, does this look OK for
> trunk/12?
OK.
> PR c++/103081
>
> gcc/cp/ChangeLog:
>
> * pt.cc (tsubst_copy) <case CONST_DECL>: Generalize
> early exit test for namespace-scope decls to check dependence of
> the enclosing scope instead. Remove dead args early exit test.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp2a/using-enum-10.C: New test.
> * g++.dg/cpp2a/using-enum-10a.C: New test.
> ---
> gcc/cp/pt.cc | 7 +------
> gcc/testsuite/g++.dg/cpp2a/using-enum-10.C | 16 ++++++++++++++++
> gcc/testsuite/g++.dg/cpp2a/using-enum-10a.C | 18 ++++++++++++++++++
> 3 files changed, 35 insertions(+), 6 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/using-enum-10.C
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/using-enum-10a.C
>
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 31691618d1b..bc8ea06ceae 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -17066,13 +17066,8 @@ tsubst_copy (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>
> if (DECL_TEMPLATE_PARM_P (t))
> return tsubst_copy (DECL_INITIAL (t), args, complain, in_decl);
> - /* There is no need to substitute into namespace-scope
> - enumerators. */
> - if (DECL_NAMESPACE_SCOPE_P (t))
> + if (!uses_template_parms (DECL_CONTEXT (t)))
> return t;
> - /* If ARGS is NULL, then T is known to be non-dependent. */
> - if (args == NULL_TREE)
> - return scalar_constant_value (t);
>
> /* Unfortunately, we cannot just call lookup_name here.
> Consider:
> diff --git a/gcc/testsuite/g++.dg/cpp2a/using-enum-10.C b/gcc/testsuite/g++.dg/cpp2a/using-enum-10.C
> new file mode 100644
> index 00000000000..98fe0644729
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/using-enum-10.C
> @@ -0,0 +1,16 @@
> +// PR c++/103081
> +// { dg-do compile { target c++20 } }
> +
> +enum class Pig { OINK };
> +
> +struct Hog {
> + using enum Pig;
> + Hog(Pig) { }
> +};
> +
> +template<int>
> +void pen() {
> + Hog(Hog::OINK);
> +}
> +
> +template void pen<0>();
> diff --git a/gcc/testsuite/g++.dg/cpp2a/using-enum-10a.C b/gcc/testsuite/g++.dg/cpp2a/using-enum-10a.C
> new file mode 100644
> index 00000000000..43688e69b19
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/using-enum-10a.C
> @@ -0,0 +1,18 @@
> +// A version of using-enum-10.C where Hog is a template.
> +// PR c++/103081
> +// { dg-do compile { target c++20 } }
> +
> +enum class Pig { OINK };
> +
> +template<int>
> +struct Hog {
> + using enum Pig;
> + Hog(Pig) { OINK; }
> +};
> +
> +template<int N>
> +void pen() {
> + Hog<N>(Hog<N>::OINK);
> +}
> +
> +template void pen<0>();
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