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* [gcc r14-9332] c++: Fix template deduction for conversion operators with xobj parameters [PR113629]
@ 2024-03-06 9:49 Nathaniel Shead
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From: Nathaniel Shead @ 2024-03-06 9:49 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:49d83e963aa453600088380aebd507e172eb80ad
commit r14-9332-g49d83e963aa453600088380aebd507e172eb80ad
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date: Wed Mar 6 00:43:22 2024 +1100
c++: Fix template deduction for conversion operators with xobj parameters [PR113629]
Unification for conversion operators (DEDUCE_CONV) doesn't perform
transformations like handling forwarding references. This is correct in
general, but not for xobj parameters, which should be handled "normally"
for the purposes of deduction: [temp.deduct.conv] only applies to the
return type of the conversion function.
PR c++/113629
gcc/cp/ChangeLog:
* pt.cc (type_unification_real): Only use DEDUCE_CONV for the
return type of a conversion function.
gcc/testsuite/ChangeLog:
* g++.dg/cpp23/explicit-obj-conv-op.C: New test.
Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>
Diff:
---
gcc/cp/pt.cc | 12 +++++-
gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C | 49 +++++++++++++++++++++++
2 files changed, 60 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c4bc54a8fdb..a6e6c804130 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -23312,10 +23312,18 @@ type_unification_real (tree tparms,
parameter pack is a non-deduced context. */
continue;
+ /* [temp.deduct.conv] only applies to the deduction of the return
+ type, which is always the first argument here. Other arguments
+ (notably, explicit object parameters) should undergo normal
+ call-like unification. */
+ unification_kind_t kind = strict;
+ if (strict == DEDUCE_CONV && ia > 0)
+ kind = DEDUCE_CALL;
+
arg = args[ia];
++ia;
- if (unify_one_argument (tparms, full_targs, parm, arg, subr, strict,
+ if (unify_one_argument (tparms, full_targs, parm, arg, subr, kind,
explain_p))
return 1;
}
@@ -23324,6 +23332,8 @@ type_unification_real (tree tparms,
&& parms != void_list_node
&& TREE_CODE (TREE_VALUE (parms)) == TYPE_PACK_EXPANSION)
{
+ gcc_assert (strict != DEDUCE_CONV);
+
/* Unify the remaining arguments with the pack expansion type. */
tree argvec;
tree parmvec = make_tree_vec (1);
diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C b/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C
new file mode 100644
index 00000000000..a6ae4ea1dda
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/explicit-obj-conv-op.C
@@ -0,0 +1,49 @@
+// PR c++/113629
+// { dg-do compile { target c++23 } }
+
+template <typename T> constexpr bool is_lvalue = false;
+template <typename T> constexpr bool is_lvalue<T&> = true;
+
+struct A {
+ constexpr operator bool(this auto&& self) {
+ return is_lvalue<decltype(self)>;
+ }
+};
+
+constexpr A a;
+static_assert(static_cast<bool>(a));
+static_assert((bool)a);
+static_assert(!static_cast<bool>(A{}));
+static_assert(!(bool)A{});
+
+struct B : A {};
+
+constexpr B b;
+static_assert(static_cast<bool>(b));
+static_assert((bool)b);
+static_assert(!static_cast<bool>(B{}));
+static_assert(!(bool)B{});
+
+struct C {
+ template <typename R, typename T>
+ explicit constexpr operator R(this T&&) {
+ return is_lvalue<T>;
+ }
+};
+
+constexpr C c;
+static_assert(static_cast<bool>(c));
+static_assert((bool)c);
+static_assert(!static_cast<bool>(C{}));
+static_assert(!(bool)C{});
+
+struct D {
+ explicit constexpr operator bool(this const D&) { return true; }
+ explicit constexpr operator bool(this const D&&) { return false; }
+};
+
+constexpr D d;
+static_assert(static_cast<bool>(d));
+static_assert((bool)d);
+static_assert(!static_cast<bool>(D{}));
+static_assert(!(bool)D{});
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