c++: Fix error recovery of invalid splice during tsubst_splice_expr [PR123752]

splice can return error_mark_node, e.g. if the evaluation of the
constant expression throws without being caught, and the error_mark_node
later on causes ICEs in various asserts.

The following patch fixes it by returning early if error_mark_node is
returned.

2026-02-07  Jakub Jelinek  <jakub@redhat.com>

	PR c++/123752
	* pt.cc (tsubst_splice_expr): Return error_mark_node if
	splice returned it.

	* g++.dg/reflect/splice8.C: New test.

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 50966de76f8d1d30f6578b4624603974dd992c0a..049bbf07e015768ca5d004627110ea39cea3423f 100644 (file)
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -16753,6 +16753,8 @@ tsubst_splice_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
   if (op == error_mark_node)
     return error_mark_node;
   op = splice (op);
+  if (op == error_mark_node)
+    return error_mark_node;
   if (dependent_splice_p (op))
     {
       if (SPLICE_EXPR_EXPRESSION_P (t))

diff --git a/gcc/testsuite/g++.dg/reflect/splice8.C b/gcc/testsuite/g++.dg/reflect/splice8.C
new file mode 100644 (file)
index 0000000..5ca2846
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/splice8.C
@@ -0,0 +1,33 @@
+// PR c++/123752
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+
+struct S { int s; };
+struct U { int u; };
+
+template <typename T>
+consteval decltype (^^int)
+foo ()
+{
+  return ^^S::s;
+}
+
+template <>
+consteval decltype (^^int)
+foo <U> ()
+{
+  throw 1;
+}
+
+template <typename T>
+auto
+bar (T x)
+{
+  return x.[: foo <T> () :];   // { dg-error "uncaught exception '1'" }
+}
+
+auto
+baz (U x)
+{
+  return bar (x);
+}