On 6/14/25 8:19 AM, Iain Sandoe wrote:
Hi Jason,
It seems that we had not been marking typeid expressions as unevaluated
so that is also added here.
This seems to be https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68604
But only some typeid expressions are unevaluated; the
https://eel.is/c++draft/expr#typeid-4 case (polymorphic glvalue) is not.
....
In any case let's not mess with it in this patch.
Removed, added a note and xfailed the test for it, so that once we get a
resolution to PR68604 it should just start XPASSing and we're done.
OK for trunk?
OK.
thanks
Iain
--- 8< ---
From [expr.await]/2
We should not accept co_await, co_yield in unevaluated contexts.
Currently (see PR68604) we do not mark typeid expressions as unevaluated
since the standard rules mean that this depends on the value type.
gcc/cp/ChangeLog:
* coroutines.cc (finish_co_await_expr): Do not allow in an
unevaluated context.
(finish_co_yield_expr): Likewise.
gcc/testsuite/ChangeLog:
* g++.dg/coroutines/unevaluated.C: New test.
Signed-off-by: Iain Sandoe <i...@sandoe.co.uk>
---
gcc/cp/coroutines.cc | 12 +++++++++
gcc/testsuite/g++.dg/coroutines/unevaluated.C | 25 +++++++++++++++++++
2 files changed, 37 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/coroutines/unevaluated.C
diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index a1986282ca7..6b3fe540376 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -1549,6 +1549,12 @@ finish_co_await_expr (location_t kw, tree expr)
if (!expr || error_operand_p (expr))
return error_mark_node;
+ if (cp_unevaluated_operand)
+ {
+ error_at (kw, "%qs cannot be used in an unevaluated context","co_await");
+ return error_mark_node;
+ }
+
if (!coro_common_keyword_context_valid_p (current_function_decl, kw,
"co_await"))
return error_mark_node;
@@ -1629,6 +1635,12 @@ finish_co_yield_expr (location_t kw, tree expr)
if (!expr || error_operand_p (expr))
return error_mark_node;
+ if (cp_unevaluated_operand)
+ {
+ error_at (kw, "%qs cannot be used in an unevaluated context","co_yield");
+ return error_mark_node;
+ }
+
/* Check the general requirements and simple syntax errors. */
if (!coro_common_keyword_context_valid_p (current_function_decl, kw,
"co_yield"))
diff --git a/gcc/testsuite/g++.dg/coroutines/unevaluated.C
b/gcc/testsuite/g++.dg/coroutines/unevaluated.C
new file mode 100644
index 00000000000..63dae38dea3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/unevaluated.C
@@ -0,0 +1,25 @@
+// { dg-additional-options "-fsyntax-only" }
+#include <typeinfo>
+#include <coroutine>
+
+struct Task {
+ struct promise_type {
+ promise_type() = default;
+ Task get_return_object() { return {}; }
+ std::suspend_never initial_suspend() { return {}; }
+ std::suspend_always final_suspend() noexcept { return {}; }
+ void unhandled_exception() {}
+ void return_void () {}
+ std::suspend_never yield_value (int) { return {}; }
+ };
+};
+
+// We do not permit co_await, co_yield outside a function, and so uses in
+// noexcept or requirements are covered by that.
+Task foo() {
+ /* This one will currently fail - see PR68604. */
+ const std::type_info& ti1 = typeid (co_await std::suspend_never{}); // { dg-error
{'co_await' cannot be used in an unevaluated context} "" { xfail *-*-* } }
+ std::size_t x = sizeof (co_yield (19)); // { dg-error {'co_yield' cannot
be used in an unevaluated context} }
+ decltype (co_await std::suspend_never{}) A; // { dg-error {'co_await'
cannot be used in an unevaluated context} }
+ co_return;
+}
