C++ PATCH for c++/57047 (ICE with constexpr)

[Jason Merrill <jason at redhat dot com>]

Oddly, after you assign to a variable, you can't use its old value 
anymore...

Tested x86_64-pc-linux-gnu, applying to trunk, 4.8, 4.7.

commit 16ee0ee2c495bc475e0ba015c6b9fd4707692196
Author: jason <jason@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Fri May 10 14:17:37 2013 +0000

    	PR c++/57047
    	* semantics.c (cxx_fold_indirect_ref): Fix thinko.
    
    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@198777 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index d0db10a..3e78887 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -7643,15 +7643,17 @@ cxx_fold_indirect_ref (location_t loc, tree type, tree op0, bool *empty_base)
 	    }
 	}
     }
-  /* *(foo *)fooarrptreturn> (*fooarrptr)[0] */
+  /* *(foo *)fooarrptr => (*fooarrptr)[0] */
   else if (TREE_CODE (TREE_TYPE (subtype)) == ARRAY_TYPE
 	   && (same_type_ignoring_top_level_qualifiers_p
 	       (type, TREE_TYPE (TREE_TYPE (subtype)))))
     {
       tree type_domain;
       tree min_val = size_zero_node;
-      sub = cxx_fold_indirect_ref (loc, TREE_TYPE (subtype), sub, NULL);
-      if (!sub)
+      tree newsub = cxx_fold_indirect_ref (loc, TREE_TYPE (subtype), sub, NULL);
+      if (newsub)
+	sub = newsub;
+      else
 	sub = build1_loc (loc, INDIRECT_REF, TREE_TYPE (subtype), sub);
       type_domain = TYPE_DOMAIN (TREE_TYPE (sub));
       if (type_domain && TYPE_MIN_VALUE (type_domain))
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-array-ptr8.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-array-ptr8.C
new file mode 100644
index 0000000..ee425ea
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-array-ptr8.C
@@ -0,0 +1,54 @@
+// PR c++/57047
+// { dg-require-effective-target c++11 }
+
+template <typename>
+struct A;
+template <typename T>
+struct A <T &>
+{
+  typedef T type;
+};
+template <typename T>
+constexpr T && foo (typename A <T>::type & __t) noexcept
+{
+  return static_cast <T &&>(__t);
+}
+template <class T1, class T2>
+struct B
+{
+  T1 t1;
+  T2 t2;
+  template <class U>
+  constexpr B (U && __x, const T2 & __y) : t1 (foo <U> (__x)), t2 (__y) {}
+};
+static inline constexpr bool
+fn1 (const char c)
+{
+  return ('0' <= c) && (c <= '9');
+}
+static inline constexpr bool
+fn2 (const char c)
+{
+  return (('A' <= c) && (c <= 'Z')) || (('a' <= c) && (c <= 'z'));
+}
+static constexpr bool
+fn3 (const char *const x)
+{
+  return (x[1] == '\0' && x[0] == ']') ? true : (!fn1 (x[0])) ? false : fn3 (&x[1]);
+}
+static constexpr bool
+fn4 (const char *const x)
+{
+  return (x[0] == '\0') ? fn3 (&x[1]) : fn4 (&x[1]);
+}
+static inline constexpr bool
+fn5 (const char *const x)
+{
+  return fn2 (x[0]) ? fn4 (x) : false;
+}
+struct C final
+{
+  constexpr C (const char *const t1) : c (fn5 (t1) ? 199 : 69) {}
+  unsigned c;
+};
+B <C, C> p ("a", "b");