C++ PATCH for c++/91819 - ICE with operator++ and enum.

[Marek Polacek]

This is an ICE that started with the recent r275745.  The problem here is that
for a POSTINCREMENT_EXPR build_new_op_1 is called with null arg2, so arg2_type 
is
also null after
 5819   tree arg2_type = arg2 ? unlowered_expr_type (arg2) : NULL_TREE;
but then we make arg2 nonnull
 5887   if (code == POSTINCREMENT_EXPR || code == POSTDECREMENT_EXPR)
 5888     arg2 = integer_zero_node;
while arg2_type is still null and so
 5940   else if (! arg2 || ! CLASS_TYPE_P (arg2_type))
crashes.  Fixed by setting arg2_type in the ++/-- case.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2019-09-19  Marek Polacek  <pola...@redhat.com>

        PR c++/91819 - ICE with operator++ and enum.
        * call.c (build_new_op_1): Set arg2_type.

        * g++.dg/other/operator4.C: New test.

diff --git gcc/cp/call.c gcc/cp/call.c
index b780b0af58e..512421b4772 100644
--- gcc/cp/call.c
+++ gcc/cp/call.c
@@ -5878,7 +5878,10 @@ build_new_op_1 (const op_location_t &loc, enum tree_code 
code, int flags,
     goto builtin;
 
   if (code == POSTINCREMENT_EXPR || code == POSTDECREMENT_EXPR)
-    arg2 = integer_zero_node;
+    {
+      arg2 = integer_zero_node;
+      arg2_type = integer_type_node;
+    }
 
   vec_alloc (arglist, 3);
   arglist->quick_push (arg1);
diff --git gcc/testsuite/g++.dg/other/operator4.C 
gcc/testsuite/g++.dg/other/operator4.C
new file mode 100644
index 00000000000..e7a41c01a58
--- /dev/null
+++ gcc/testsuite/g++.dg/other/operator4.C
@@ -0,0 +1,22 @@
+// PR c++/91819 - ICE with operator++ and enum.
+// { dg-do compile }
+
+enum Foo
+{
+  a,
+  b
+};
+
+inline Foo operator++(Foo &f, int) 
+{
+  return f = (Foo)(f + 1);
+}
+
+int main()
+{
+  int count = 0;
+  for (Foo f = a; f <= b; f++) {
+    count++;
+  }
+  return count;
+}