[committed] Fix OpenMP C++ reduction error recovery (PR c++/84791)

[Jakub Jelinek]

Hi!

The following patch removes errorneous reduction clause already during
parsing, so that we don't ICE on it during instantiation.

Bootstrapped/regtested on x86_64-linux and i686-linux, committed to trunk.

2018-03-30  Jakub Jelinek  <ja...@redhat.com>

        PR c++/84791
        * semantics.c (finish_omp_reduction_clause): If
        OMP_CLAUSE_REDUCTION_PLACEHOLDER is error_mark_node, return true
        even if processing_template_decl.

        * g++.dg/gomp/pr84791.C: New test.

--- gcc/cp/semantics.c.jj       2018-03-23 21:33:56.279959167 +0100
+++ gcc/cp/semantics.c  2018-03-29 14:42:05.759995585 +0200
@@ -5623,7 +5623,11 @@ finish_omp_reduction_clause (tree c, boo
       return false;
     }
   else if (processing_template_decl)
-    return false;
+    {
+      if (OMP_CLAUSE_REDUCTION_PLACEHOLDER (c) == error_mark_node)
+       return true;
+      return false;
+    }
 
   tree id = OMP_CLAUSE_REDUCTION_PLACEHOLDER (c);
 
--- gcc/testsuite/g++.dg/gomp/pr84791.C.jj      2018-03-29 14:35:04.377774216 
+0200
+++ gcc/testsuite/g++.dg/gomp/pr84791.C 2018-03-29 14:37:17.491839303 +0200
@@ -0,0 +1,15 @@
+// PR c++/84791
+// { dg-do compile }
+
+typedef int I;
+
+template <int>
+void
+foo ()
+{
+  I i;
+  #pragma omp parallel reduction (I::I: i)     // { dg-error "'I' is not a 
class, namespace, or enumeration" "" { target c++11 } }
+    ;                                          // { dg-error "'I' is not a 
class or namespace" "" { target c++98_only } .-1 }
+}
+
+template void foo<0> ();

        Jakub