C++ PATCH for c++/67108 (ICE with constexpr and tree dumps)

[Jason Merrill <jason at redhat dot com>]

We can't do tsubsting once cgraph starts throwing away front end 
information; use the at_eof flag to communicate that we've reached that 
point.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit 61a9d0354261705979003d15ebd7c97605d6dc2e
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Aug 12 15:54:06 2015 +0100

    	PR c++/67108
    	* decl2.c (c_parse_final_cleanups): Set at_eof to 2 at end.
    	* error.c (dump_template_bindings): Don't tsubst in that case.

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 78fd4af..ab6b3ec 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -4797,7 +4797,8 @@ extern GTY(()) vec<tree, va_gc> *local_classes;
 #endif /* !defined(NO_DOLLAR_IN_LABEL) || !defined(NO_DOT_IN_LABEL) */
 
 
-/* Nonzero if we're done parsing and into end-of-file activities.  */
+/* Nonzero if we're done parsing and into end-of-file activities.
+   Two if we're done with front-end processing.  */
 
 extern int at_eof;
 
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 068d79c..8e7a453 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -4846,6 +4846,9 @@ c_parse_final_cleanups (void)
 
   timevar_stop (TV_PHASE_DEFERRED);
   timevar_start (TV_PHASE_PARSING);
+
+  /* Indicate that we're done with front end processing.  */
+  at_eof = 2;
 }
 
 /* Perform any post compilation-proper cleanups for the C++ front-end.
diff --git a/gcc/cp/error.c b/gcc/cp/error.c
index ae3e092..faf8744 100644
--- a/gcc/cp/error.c
+++ b/gcc/cp/error.c
@@ -339,6 +339,11 @@ dump_template_bindings (cxx_pretty_printer *pp, tree parms, tree args,
       && !DECL_LANG_SPECIFIC (current_function_decl))
     return;
 
+  /* Don't try to do this once cgraph starts throwing away front-end
+     information.  */
+  if (at_eof >= 2)
+    return;
+
   FOR_EACH_VEC_SAFE_ELT (typenames, i, t)
     {
       if (need_semicolon)
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-targ3.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-targ3.C
new file mode 100644
index 0000000..d1e4482
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-targ3.C
@@ -0,0 +1,40 @@
+// PR c++/67108
+// { dg-do compile { target c++11 } }
+
+template < typename, typename > struct is_same;
+template < typename T > struct is_same <T, T >
+{
+  enum
+  {
+    value = true
+  }
+   ;
+    constexpr bool operator () ()
+  {
+    return value;
+  }
+}
+ ;
+template < bool, typename = void >struct enable_if;
+template < typename T > struct enable_if <true, T >
+{
+  typedef T type;
+}
+ ;
+struct A;
+template < typename, typename = void >struct F;
+template < typename X > struct F <X, typename enable_if < is_same < X, A >
+{
+}
+  () >::type >
+{
+  template < typename MakeDependent > F (MakeDependent)
+  {
+  }
+}
+;
+
+int main ()
+{
+  F < A > (1);
+}