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c++: alias CTAD in unevaluated context [PR101233]

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This is the alias CTAD version of the CTAD bug PR93248, and the fix is
the same: clear cp_unevaluated_operand so that the entire chain of
DECL_ARGUMENTS gets substituted.

	PR c++/101233

gcc/cp/ChangeLog:

	* pt.c (alias_ctad_tweaks): Clear cp_unevaluated_operand for
	substituting DECL_ARGUMENTS.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/class-deduction-alias10.C: New test.
This commit is contained in:
Patrick Palka 2021-07-16 16:21:13 -04:00
parent d04b0c7579
commit a8b3861496
2 changed files with 17 additions and 1 deletions
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8
gcc/cp/pt.c
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@ -29097,7 +29097,13 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
/* Substitute the deduced arguments plus the rewritten template
parameters into f to get g. This covers the type, copyness,
guideness, and explicit-specifier. */
tree g = tsubst_decl (DECL_TEMPLATE_RESULT (f), targs, complain);
tree g;
{
/* Parms are to have DECL_CHAIN tsubsted, which would be skipped
if cp_unevaluated_operand. */
cp_evaluated ev;
g = tsubst_decl (DECL_TEMPLATE_RESULT (f), targs, complain);
}
if (g == error_mark_node)
continue;
DECL_USE_TEMPLATE (g) = 0;

10
gcc/testsuite/g++.dg/cpp2a/class-deduction-alias10.C Normal file
View file

@ -0,0 +1,10 @@
// PR c++/101233
// { dg-do compile { target c++20 } }
template<class T, class U>
struct A { A(T, U); };
template<class T, class U>
using B = A<U, T>;
using type = decltype(B{0, 0});