On 7/15/21 12:37 PM, Patrick Palka wrote:
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.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk/11?
OK.
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.
---
gcc/cp/pt.c | 12 +++++++++---
gcc/testsuite/g++.dg/cpp2a/class-deduction-alias10.C | 10 ++++++++++
2 files changed, 19 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-alias10.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index c7bf7d412ca..bc0a0936579 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -29097,9 +29097,15 @@ 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);
- if (g == error_mark_node)
- continue;
+ 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;
fprime = build_template_decl (g, gtparms, false);
DECL_TEMPLATE_RESULT (fprime) = g;
diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias10.C
b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias10.C
new file mode 100644
index 00000000000..a473fff5dc7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias10.C
@@ -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});
