3 files changed, 33 insertions, 1 deletions
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index c536eb581a7..d339036e88e 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -5173,12 +5173,15 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p, walk_tree_fn func,
   result = NULL_TREE;
   switch (code)
     {
+    case TEMPLATE_TYPE_PARM:
+      if (template_placeholder_p (*tp))
+	WALK_SUBTREE (CLASS_PLACEHOLDER_TEMPLATE (*tp));
+      /* Fall through.  */
     case DEFERRED_PARSE:
     case TEMPLATE_TEMPLATE_PARM:
     case BOUND_TEMPLATE_TEMPLATE_PARM:
     case UNBOUND_CLASS_TEMPLATE:
     case TEMPLATE_PARM_INDEX:
-    case TEMPLATE_TYPE_PARM:
     case TYPEOF_TYPE:
     case UNDERLYING_TYPE:
       /* None of these have subtrees other than those already walked
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ctad1.C b/gcc/testsuite/g++.dg/cpp2a/concepts-ctad1.C
new file mode 100644
index 00000000000..ec2e4b014d7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ctad1.C
@@ -0,0 +1,16 @@
+// PR c++/98611
+// { dg-do compile { target c++20 } }
+
+template <class T, class U>
+concept IsSame = __is_same(T, U);
+
+template <class T, template <class...> class _Class>
+concept IsInstantiationOf = requires(T object) {
+ { _Class{object} } -> IsSame<T>;
+};
+
+template <class T> struct Degrees {};
+static_assert(IsInstantiationOf<Degrees<int>, Degrees>);
+
+template <class T> struct NotDegrees {};
+static_assert(!IsInstantiationOf<Degrees<int>, NotDegrees>);
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-ctad2.C b/gcc/testsuite/g++.dg/cpp2a/concepts-ctad2.C
new file mode 100644
index 00000000000..0d7f9790777
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-ctad2.C
@@ -0,0 +1,13 @@
+// PR c++/98611
+// { dg-do compile { target c++20 } }
+
+template <class>
+struct S {
+  template <class T> struct Tmpl { Tmpl(T); };
+
+  template <class T>
+    requires requires (T object) { Tmpl{object}; }
+  static int f(T);
+};
+
+int a = S<int>::f(0);