From: Patrick Palka <ppalka@redhat.com>
Date: Wed, 15 Nov 2023 17:17:55 +0000 (-0500)
Subject: c++: partially inst requires-expr in noexcept-spec [PR101043]
X-Git-Tag: basepoints/gcc-15~4635
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=40a7707a7ea3568cee2cd80cd7e83b7eda678410;p=thirdparty%2Fgcc.git

c++: partially inst requires-expr in noexcept-spec [PR101043]

Here we're ICEing from strip_typedefs for the partially instantiated
requires-expression when walking its REQUIRES_EXPR_EXTRA_ARGS which
in this case is a TREE_LIST with non-empty TREE_PURPOSE (to hold the
captured local specialization 't' as per build_extra_args) which
strip_typedefs doesn't expect.

We can probably skip walking REQUIRES_EXPR_EXTRA_ARGS at all since it
shouldn't contain any typedefs in the first place, but it seems safer
and more generally useful to just teach strip_typedefs to handle non-empty
TREE_PURPOSE the obvious way.  (The code asserts TREE_PURPOSE was empty
even since since its inception i.e. r189298.)

	PR c++/101043

gcc/cp/ChangeLog:

	* tree.cc (strip_typedefs_expr) <case TREE_LIST>: Handle
	non-empty TREE_PURPOSE.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-requires37.C: New test.
---

diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index dc4126f935c3..0736e8d8f485 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -1911,19 +1911,24 @@ strip_typedefs_expr (tree t, bool *remove_attributes, unsigned int flags)
     case TREE_LIST:
       {
 	bool changed = false;
-	releasing_vec vec;
+	auto_vec<tree_pair, 4> vec;
 	r = t;
 	for (; t; t = TREE_CHAIN (t))
 	  {
-	    gcc_assert (!TREE_PURPOSE (t));
-	    tree elt = strip_typedefs (TREE_VALUE (t),
-				       remove_attributes, flags);
-	    if (elt != TREE_VALUE (t))
+	    tree purpose = strip_typedefs (TREE_PURPOSE (t),
+					   remove_attributes, flags);
+	    tree value = strip_typedefs (TREE_VALUE (t),
+					 remove_attributes, flags);
+	    if (purpose != TREE_PURPOSE (t) || value != TREE_VALUE (t))
 	      changed = true;
-	    vec_safe_push (vec, elt);
+	    vec.safe_push ({purpose, value});
 	  }
 	if (changed)
-	  r = build_tree_list_vec (vec);
+	  {
+	    r = NULL_TREE;
+	    for (int i = vec.length () - 1; i >= 0; i--)
+	      r = tree_cons (vec[i].first, vec[i].second, r);
+	  }
 	return r;
       }
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires37.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires37.C
new file mode 100644
index 000000000000..fa4095ed494f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires37.C
@@ -0,0 +1,11 @@
+// PR c++/101043
+// { dg-do compile { target c++20 } }
+
+template<class T>
+void f(T t) {
+  [&](auto) noexcept(requires { t.g(); }) { }(0);
+}
+
+int main() {
+  f(0);
+}