[gcc(refs/vendors/ARM/heads/arm-perf-staging)] c++: Fix ICE-after-error on partial spec [92068]

[Tamar Christina]

https://gcc.gnu.org/g:3a285529ee338ef2867ae7add26b6493f004bf0d

commit 3a285529ee338ef2867ae7add26b6493f004bf0d
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Mar 14 17:10:39 2020 -0400

    c++: Fix ICE-after-error on partial spec [92068]
    
    Here the template arguments for the partial specialization are valid
    arguments for the template, but not for a partial specialization, because
    'd' can never be deduced to anything other than an empty pack.
    
    gcc/cp/ChangeLog
    2020-03-14  Jason Merrill  <jason@redhat.com>
    
            PR c++/92068
            * pt.c (process_partial_specialization): Error rather than crash on
            extra pack expansion.

Diff:
---
 gcc/cp/ChangeLog                         | 6 ++++++
 gcc/cp/pt.c                              | 9 ++++++++-
 gcc/testsuite/g++.dg/cpp0x/variadic178.C | 6 ++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index bb7f590ea0b..c9375234c41 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-14  Jason Merrill  <jason@redhat.com>
+
+	PR c++/92068
+	* pt.c (process_partial_specialization): Error rather than crash on
+	extra pack expansion.
+
 2020-03-14  Jason Merrill  <jason@redhat.com>
 
 	PR c++/92909
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index bd2f9be82ea..48ac48615a0 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -5038,6 +5038,14 @@ process_partial_specialization (tree decl)
       return decl;
     }
 
+  else if (nargs > DECL_NTPARMS (maintmpl))
+    {
+      error ("too many arguments for partial specialization %qT", type);
+      inform (DECL_SOURCE_LOCATION (maintmpl), "primary template here");
+      /* Avoid crash below.  */
+      return decl;
+    }
+
   /* If we aren't in a dependent class, we can actually try deduction.  */
   else if (tpd.level == 1
 	   /* FIXME we should be able to handle a partial specialization of a
@@ -5064,7 +5072,6 @@ process_partial_specialization (tree decl)
 
      Also, we verify that pack expansions only occur at the
      end of the argument list.  */
-  gcc_assert (nargs == DECL_NTPARMS (maintmpl));
   tpd2.parms = 0;
   for (i = 0; i < nargs; ++i)
     {
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic178.C b/gcc/testsuite/g++.dg/cpp0x/variadic178.C
new file mode 100644
index 00000000000..f0e65958de3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic178.C
@@ -0,0 +1,6 @@
+// PR c++/92068
+// { dg-do compile { target c++11 } }
+
+template <typename, typename> struct a;
+template <typename b, typename c, typename... d>
+struct a<b, c, d...> { };	// { dg-error "arguments" }