diff options
| author | Patrick Palka <ppalka@redhat.com> | 2025-03-22 10:15:52 -0400 |
|---|---|---|
| committer | Patrick Palka <ppalka@redhat.com> | 2025-03-22 10:15:52 -0400 |
| commit | df5fa3a3d0d7f2413c832548c88f76dfe67802fd (patch) | |
| tree | faea47daac6af9f6945945da4b78565ef99ec772 /gcc | |
| parent | 4f9e72dd364915dafc03202cc6ad9ddffaee93f3 (diff) | |
| download | gcc-df5fa3a3d0d7f2413c832548c88f76dfe67802fd.zip gcc-df5fa3a3d0d7f2413c832548c88f76dfe67802fd.tar.gz gcc-df5fa3a3d0d7f2413c832548c88f76dfe67802fd.tar.bz2 | |
c++: structural equality and partially inst typedef [PR119379]
Complex alias templates (and their dependent specializations) always use
structural equality because we need to treat them as transparent in some
contexts but not others. Structural-ness however wasn't being preserved
during partial instantiation, which for the below testcase leads to the
checking ICE
same canonical type node for different types 'S<int>::P<U>' and 'pair<int, U>'
when comparing those two types with comparing_dependent_aliases set
(from alias_ctad_tweaks).
This patch fixes this by making us preserve structural-ness for
partially instantiated typedefs in general.
PR c++/119379
gcc/cp/ChangeLog:
* pt.cc (tsubst_decl) <case TYPE_DECL>: Preserve structural-ness
of a partially instantiated typedef.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/class-deduction-alias24.C: New test.
Reviewed-by: Jason Merrill <jason@redhat.com>
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/cp/pt.cc | 5 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/cpp2a/class-deduction-alias24.C | 16 |
2 files changed, 21 insertions, 0 deletions
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 538ff22..39c0ee6 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -15920,6 +15920,11 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain, if (TYPE_USER_ALIGN (TREE_TYPE (t))) TREE_TYPE (r) = build_aligned_type (TREE_TYPE (r), TYPE_ALIGN (TREE_TYPE (t))); + + /* Preserve structural-ness of a partially instantiated typedef. */ + if (TYPE_STRUCTURAL_EQUALITY_P (TREE_TYPE (t)) + && dependent_type_p (TREE_TYPE (r))) + SET_TYPE_STRUCTURAL_EQUALITY (TREE_TYPE (r)); } layout_decl (r, 0); diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias24.C b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias24.C new file mode 100644 index 0000000..cceddac --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias24.C @@ -0,0 +1,16 @@ +// PR c++/119379 +// { dg-do compile { target c++20 } } + +template<class T, class U> +struct pair { + pair(T, U); +}; + +template<class T> +struct S { + template<class U> requires true + using P = pair<T, U>; +}; + +using type = decltype(S<int>::P(1, 2)); +using type = S<int>::P<int>; |