[PATCH] c++: partial ordering with memfn pointer cst [PR108104]

[Patrick Palka via Gcc-patches]

Here we're triggering an overzealous assert in unify during partial
ordering since the member function pointer constants are represented as
ordinary CONSTRUCTORs (with TYPE_PTRMEMFUNC_P TREE_TYPE) but the assert
expects only COMPOUND_LITERAL_P constructors.

Bootstrapped and regtested on x86_64-pc-linux, does this look OK for
trunk and perhaps 12?

        PR c++/108104

gcc/cp/ChangeLog:

        * pt.cc (unify) <default>: Relax assert to accept any
        CONSTRUCTOR not just COMPOUND_LITERAL_P ones.

gcc/testsuite/ChangeLog:

        * g++.dg/template/ptrmem33.C: New test.
---
 gcc/cp/pt.cc                             |  2 +-
 gcc/testsuite/g++.dg/template/ptrmem33.C | 30 ++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/template/ptrmem33.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 2f0f7a39698..44058d30799 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -24921,7 +24921,7 @@ unify (tree tparms, tree targs, tree parm, tree arg, 
int strict,
       if (is_overloaded_fn (parm) || type_unknown_p (parm))
        return unify_success (explain_p);
       gcc_assert (EXPR_P (parm)
-                 || COMPOUND_LITERAL_P (parm)
+                 || TREE_CODE (parm) == CONSTRUCTOR
                  || TREE_CODE (parm) == TRAIT_EXPR);
     expr:
       /* We must be looking at an expression.  This can happen with
diff --git a/gcc/testsuite/g++.dg/template/ptrmem33.C 
b/gcc/testsuite/g++.dg/template/ptrmem33.C
new file mode 100644
index 00000000000..dca741ae5e2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/ptrmem33.C
@@ -0,0 +1,30 @@
+// PR c++/108104
+// { dg-do compile { target c++11 } }
+
+struct A {
+  void x();
+  void y();
+};
+
+enum State { On };
+
+template<State state, void (A::*)()>
+struct B {
+  static void f();
+};
+
+template<State state>
+struct B<state, nullptr> {
+  static void g();
+};
+
+template<State state>
+struct B<state, &A::y> {
+  static void h();
+};
+
+int main() {
+  B<State::On, &A::x>::f();
+  B<State::On, nullptr>::g();
+  B<State::On, &A::y>::h();
+}
-- 
2.39.0.56.g57e2c6ebbe