C++ PATCH for c++/47950 (ICE with condition in template)

[Jason Merrill <jason at redhat dot com>]

The problem here was that we were folding the initializer too many 
times, so we lost the TREE_CONSTANT on the TARGET_EXPR.  Since we 
already fold in cp_parser_initializer_clause, it's redundant to do so in 
cp_parser_condition as well.

Tested x86_64-pc-linux-gnu, applied to trunk.
commit 957aeb5f4740118464432ab93fd6909c43eb0d28
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Mar 2 17:46:35 2011 -0500

    	PR c++/47950
    	* parser.c (cp_parser_condition): Don't fold_non_dependent_expr here.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index c63d5b3..510fcb1 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -8687,9 +8687,6 @@ cp_parser_condition (cp_parser* parser)
 	  if (BRACE_ENCLOSED_INITIALIZER_P (initializer))
 	    maybe_warn_cpp0x (CPP0X_INITIALIZER_LISTS);
 
-	  if (!non_constant_p)
-	    initializer = fold_non_dependent_expr (initializer);
-
 	  /* Process the initializer.  */
 	  cp_finish_decl (decl,
 			  initializer, !non_constant_p,
diff --git a/gcc/testsuite/g++.dg/cpp0x/regress/condition1.C b/gcc/testsuite/g++.dg/cpp0x/regress/condition1.C
new file mode 100644
index 0000000..0346764
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/regress/condition1.C
@@ -0,0 +1,80 @@
+// PR c++/47950
+// { dg-options -std=c++0x }
+
+template <typename T> struct empty
+{
+   // allow success case to build (not relevant to bug)
+   operator bool() { return true; }
+};
+
+template <typename T> struct from_int
+{
+   from_int(int) {}
+
+   // allow success case to build (not relevant to bug)
+   operator bool() { return true; }
+};
+
+template <typename T>
+from_int<T> via_function(T v)
+{
+   return from_int<T>(v);
+}
+
+template <typename T>
+void f()
+{
+   // ********* this section compiles ***********
+
+   // these plain initializers work fine
+   from_int<int> a = 7;
+   from_int<int> b = from_int<int>(7);
+   empty<int>    c = empty<int>();
+   from_int<T> ta = 7;
+   from_int<T> tb = from_int<T>(7);
+   empty<T>    tc = empty<T>();
+
+   // these dependent condition decls work fine
+   if (empty<T> x = empty<T>())
+      ;
+   if (from_int<T> x = 7)
+      ;
+   if (from_int<T> x = from_int<T>(7))
+      ;
+   if (from_int<T> x = via_function(T()))
+      ;
+
+   // this non-dependent condition decl using conversion works fine
+   if (from_int<int> x = 7)
+      ;
+
+   // these non-dependent condition decls using conversion or braced-
+   // initialization work fine (in c++0x mode only course)
+   #if __GXX_EXPERIMENTAL_CXX0X__
+   if (empty<int> x {})
+      ;
+   if (from_int<int> x {7})
+      ;
+   #endif
+
+   // ********** this section fails in C++0x ***********
+
+   // the following non-dependent condition decls cause an assertion
+   // failure in
+   //
+   //   tsubst_copy_and_build, at cp/pt.c:13370
+   //
+   // in C++0x mode
+   //
+   if (empty<int> x = empty<int>())
+      ;
+   if (from_int<int> x = from_int<int>(7))
+      ;
+   if (from_int<int> x = via_function(7))
+      ;
+}
+
+int main()
+{
+   f<int>();
+}