When regenerating a constrained lambda during instantiation of an
enclosing template, we are forgetting to substitute into the lambda's
constraints. Fix this by substituting through the constraints during
tsubst_lambda_expr.
Passes 'make check-c++', and also tested by building the testsuites of
cmcstl2 and range-v3. Does this look OK to commit to master and to the
10 branch after a full bootstrap and regtest?
gcc/cp/ChangeLog:
PR c++/92633
PR c++/92838
* pt.c (tsubst_function_decl): Don't do set_constraints when
regenerating a lambda.
(tsubst_lambda_expr): Substitute into the lambda's constraints
and do set_constraints here.
gcc/testsuite/ChangeLog:
PR c++/92633
PR c++/92838
* g++.dg/cpp2a/concepts-lambda11.C: New test.
* g++.dg/cpp2a/concepts-lambda12.C: New test.
---
gcc/cp/pt.c | 16 +++++++++++++++-
gcc/testsuite/g++.dg/cpp2a/concepts-lambda11.C | 17 +++++++++++++++++
gcc/testsuite/g++.dg/cpp2a/concepts-lambda12.C | 15 +++++++++++++++
3 files changed, 47 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-lambda11.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-lambda12.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index df647af7b46..907ca879c73 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -13854,7 +13854,10 @@ tsubst_function_decl (tree t, tree args,
tsubst_flags_t complain,
don't substitute through the constraints; that's only done when
they are checked. */
if (tree ci = get_constraints (t))
- set_constraints (r, ci);
+ /* Unless we're regenerating a lambda, in which case we'll set the
+ lambda's constraints in tsubst_lambda_expr. */
+ if (!lambda_fntype)
+ set_constraints (r, ci);
if (DECL_FRIEND_P (t) && DECL_FRIEND_CONTEXT (t))
SET_DECL_FRIEND_CONTEXT (r,
@@ -19029,6 +19032,17 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t
complain, tree in_decl)
finish_member_declaration (fn);
}
+ if (tree ci = get_constraints (oldfn))
+ {
+ /* Substitute into the lambda's constraints. */
+ if (oldtmpl)
+ ++processing_template_decl;
+ ci = tsubst_constraint_info (ci, args, complain, in_decl);
+ if (oldtmpl)
+ --processing_template_decl;
+ set_constraints (fn, ci);
+ }
+
/* Let finish_function set this. */
DECL_DECLARED_CONSTEXPR_P (fn) = false;
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda11.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda11.C
new file mode 100644
index 00000000000..dd9cd4e2344
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda11.C
@@ -0,0 +1,17 @@
+// PR c++/92838
+// { dg-do compile { target c++20 } }
+
+template<int N>
+auto foo()
+{
+ [] () requires (N != 0) { }(); // { dg-error "no match" }
+ [] () requires (N == 0) { }();
+
+ [] <int M=1> () requires (N == M) { }(); // { dg-error "no match" }
+ [] <int M=1> () requires (N != M) { }();
+}
+
+void bar()
+{
+ foo<0>();
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda12.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda12.C
new file mode 100644
index 00000000000..2bc9fd0bb25
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda12.C
@@ -0,0 +1,15 @@
+// PR c++/92633
+// { dg-do compile { target c++20 } }
+
+template<class A, class B>
+concept different_than = !__is_same_as(A, B);
+
+template<class B>
+auto diff(B) {
+ return [](different_than<B> auto a) {};
+}
+
+int main() {
+ diff(42)("");
+ diff(42)(42); // { dg-error "no match" }
+}
--
2.27.0.rc1.5.gae92ac8ae3
