From 2b27f37f90cb66e277b734c605639e2f00a2e942 Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Wed, 13 Jan 2021 13:12:14 -0500
Subject: [PATCH] c++: Crash when deducing template arguments [PR98659]

maybe_instantiate_noexcept doesn't expect to see error_mark_node, but
the new callsite I introduced in r11-6476 can pass error_mark_node to
it.  So cope.

gcc/cp/ChangeLog:

	PR c++/98659
	* pt.c (maybe_instantiate_noexcept): Return false if FN is
	error_mark_node.

gcc/testsuite/ChangeLog:

	PR c++/98659
	* g++.dg/template/deduce8.C: New test.
---
 gcc/cp/pt.c                             |  9 +++++----
 gcc/testsuite/g++.dg/template/deduce8.C | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/deduce8.C

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 12d084031b1..c9f5811980e 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -25457,7 +25457,8 @@ always_instantiate_p (tree decl)
 bool
 maybe_instantiate_noexcept (tree fn, tsubst_flags_t complain)
 {
-  tree fntype, spec, noex;
+  if (fn == error_mark_node)
+    return false;
 
   /* Don't instantiate a noexcept-specification from template context.  */
   if (processing_template_decl
@@ -25476,13 +25477,13 @@ maybe_instantiate_noexcept (tree fn, tsubst_flags_t complain)
       return !DECL_MAYBE_DELETED (fn);
     }
 
-  fntype = TREE_TYPE (fn);
-  spec = TYPE_RAISES_EXCEPTIONS (fntype);
+  tree fntype = TREE_TYPE (fn);
+  tree spec = TYPE_RAISES_EXCEPTIONS (fntype);
 
   if (!spec || !TREE_PURPOSE (spec))
     return true;
 
-  noex = TREE_PURPOSE (spec);
+  tree noex = TREE_PURPOSE (spec);
   if (TREE_CODE (noex) != DEFERRED_NOEXCEPT
       && TREE_CODE (noex) != DEFERRED_PARSE)
     return true;
diff --git a/gcc/testsuite/g++.dg/template/deduce8.C b/gcc/testsuite/g++.dg/template/deduce8.C
new file mode 100644
index 00000000000..430be426689
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/deduce8.C
@@ -0,0 +1,21 @@
+// PR c++/98659
+// { dg-do compile }
+
+template <bool> struct enable_if;
+struct function {
+  template <typename _F> void operator=(_F);
+};
+struct map {
+  function operator[](int);
+};
+enum { E };
+template <typename> void foo ();
+template <typename T>
+typename enable_if<T::value>::type foo ();
+
+void
+bar ()
+{
+  map m;
+  m[E] = foo<int>;
+}
-- 
2.30.2