This usage was intended to be allowed by P2128, but it didn't make it into
the final wording. Fixed by CWG 2507.
Tested x86_64-pc-linux-gnu, applying to trunk.
DR2507
gcc/cp/ChangeLog:
* decl.cc (grok_op_properties): Return sooner for C++23 op[].
gcc/testsuite/ChangeLog:
* g++.dg/cpp23/subscript8.C: New test.
---
gcc/cp/decl.cc | 11 +++++------
gcc/testsuite/g++.dg/cpp23/subscript8.C | 7 +++++++
2 files changed, 12 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp23/subscript8.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index b72b2a8456b..6d20765f40c 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -15331,6 +15331,11 @@ grok_op_properties (tree decl, bool complain)
"operator ()". */
return true;
+ /* C++23 allows an arbitrary number of parameters and default arguments for
+ operator[], and none of the other checks below apply. */
+ if (operator_code == ARRAY_REF && cxx_dialect >= cxx23)
+ return true;
+
if (operator_code == COND_EXPR)
{
/* 13.4.0.3 */
@@ -15344,10 +15349,6 @@ grok_op_properties (tree decl, bool complain)
{
if (!arg)
{
- /* Variadic. */
- if (operator_code == ARRAY_REF && cxx_dialect >= cxx23)
- break;
-
error_at (loc, "%qD must not have variable number of arguments",
decl);
return false;
@@ -15408,8 +15409,6 @@ grok_op_properties (tree decl, bool complain)
case OVL_OP_FLAG_BINARY:
if (arity != 2)
{
- if (operator_code == ARRAY_REF && cxx_dialect >= cxx23)
- break;
error_at (loc,
methodp
? G_("%qD must have exactly one argument")
diff --git a/gcc/testsuite/g++.dg/cpp23/subscript8.C
b/gcc/testsuite/g++.dg/cpp23/subscript8.C
new file mode 100644
index 00000000000..fe000359d41
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/subscript8.C
@@ -0,0 +1,7 @@
+// DR2507: Allow default arguments
+// { dg-additional-options {-std=c++23} }
+
+struct A
+{
+ void operator[](int, int = 42);
+};
base-commit: 0a4a2667dc115ca73b552fcabf8570620dfbe55f
--
2.31.1
