On 11/3/21 12:04, Patrick Palka wrote:
Here we're incorrectly performing unqualified lookup of 'adl' again at
substitution time for the call adl<I>(t) (for which name lookup at parse
time found nothing) which causes us to reject the testcase because the
second unqualified lookup finds the later-declared variable template
'adl', leading to confusion. Fixed thusly.
The testcase concepts-recursive-sat1.C needed to be adjusted use ADL
proper instead of relying on this incorrect behavior.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk and perhaps 11 given it's a C++20 bugfix?
OK for trunk. Not for 11, I think, as it also affects non-C++20 code.
PR c++/102670
gcc/cp/ChangeLog:
* pt.c (tsubst_copy_and_build) <case CALL_EXPR>: When looking
for an identifier callee in the koenig_p case, also look through
TEMPLATE_ID_EXPR. Use tsubst_copy to substitute through the
template arguments of the template-id.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-recursive-sat1.C:
* g++.dg/cpp2a/fn-template23.C: New test.
---
gcc/cp/pt.c | 11 +++++-
.../g++.dg/cpp2a/concepts-recursive-sat1.C | 15 +++++---
gcc/testsuite/g++.dg/cpp2a/fn-template23.C | 36 +++++++++++++++++++
3 files changed, 56 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/fn-template23.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 66040035b2f..40f84648ed2 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -20256,7 +20256,10 @@ tsubst_copy_and_build (tree t,
/*done=*/false,
/*address_p=*/false);
}
- else if (koenig_p && identifier_p (function))
+ else if (koenig_p
+ && (identifier_p (function)
+ || (TREE_CODE (function) == TEMPLATE_ID_EXPR
+ && identifier_p (TREE_OPERAND (function, 0)))))
{
/* Do nothing; calling tsubst_copy_and_build on an identifier
would incorrectly perform unqualified lookup again.
@@ -20269,6 +20272,12 @@ tsubst_copy_and_build (tree t,
FIXME but doing that causes c++/15272, so we need to stop
using IDENTIFIER_NODE in that situation. */
qualified_p = false;
+
+ if (TREE_CODE (function) == TEMPLATE_ID_EXPR)
+ /* Use tsubst_copy to substitute through the template arguments
+ of the template-id without performing unqualified lookup on
+ the template name. */
+ function = tsubst_copy (function, args, complain, in_decl);
}
else
{
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat1.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat1.C
index 22696c30d81..4c178b77946 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat1.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat1.C
@@ -3,16 +3,21 @@
template<int N, typename T>
concept Foo = requires(T t) { foo<N + 1>(t); }; // { dg-error "template
instantiation depth" }
-template<int N = 1, typename T = int>
- requires Foo<N, T>
-int foo(T t)
+namespace ns
{
- return foo<N + 1>(t);
+ struct S { };
+
+ template<int N, typename T>
+ requires Foo<N, T>
+ int foo(T t)
+ {
+ return foo<N + 1>(t);
+ }
}
int main(int, char**)
{
- return foo<1>(1);
+ return ns::foo<1>(ns::S{});
}
// { dg-prune-output "compilation terminated" }
diff --git a/gcc/testsuite/g++.dg/cpp2a/fn-template23.C
b/gcc/testsuite/g++.dg/cpp2a/fn-template23.C
new file mode 100644
index 00000000000..b85d4c96dab
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/fn-template23.C
@@ -0,0 +1,36 @@
+// PR c++/102670
+// { dg-do compile { target c++20 } }
+
+namespace ns {
+ struct S { };
+
+ template<int I>
+ constexpr int adl(const S &) {
+ return I;
+ }
+}
+
+namespace redirect {
+ template<class T, int I>
+ concept can_call_adl = requires(T t) {
+ adl<I>(t);
+ };
+
+ template<int I>
+ struct adl_fn {
+ template<can_call_adl<I> T>
+ constexpr decltype(auto) operator()(T t) const {
+ return adl<I>(t);
+ }
+ };
+
+ namespace {
+ template<int I>
+ constexpr inline adl_fn<I> adl{};
+ }
+}
+
+int main() {
+ static_assert(redirect::can_call_adl<ns::S, 3>);
+ redirect::adl<3>(ns::S{});
+}
