C++ PATCH to allow constexpr ctor with typedef declaration in C++11 (c++/70229)

[Marek Polacek]

In C++11, constexpr constructor must have an empty body except for
several cases, one of them being:
- typedef declarations and alias-declarations that do not define
  classes or enumerations
But we were rejecting constexpr constructors consisting of a typedef
declaration only.

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

2016-08-03  Marek Polacek  <pola...@redhat.com>

        PR c++/70229
        * constexpr.c (check_constexpr_ctor_body_1): Allow typedef
        declarations.

        * g++.dg/cpp0x/constexpr-ctor19.C: New test.

diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
index edade48..41665c5 100644
--- gcc/cp/constexpr.c
+++ gcc/cp/constexpr.c
@@ -425,7 +425,8 @@ check_constexpr_ctor_body_1 (tree last, tree list)
   switch (TREE_CODE (list))
     {
     case DECL_EXPR:
-      if (TREE_CODE (DECL_EXPR_DECL (list)) == USING_DECL)
+      if (TREE_CODE (DECL_EXPR_DECL (list)) == USING_DECL
+         || TREE_CODE (DECL_EXPR_DECL (list)) == TYPE_DECL)
        return true;
       return false;
 
diff --git gcc/testsuite/g++.dg/cpp0x/constexpr-ctor19.C 
gcc/testsuite/g++.dg/cpp0x/constexpr-ctor19.C
index e69de29..f5ef053 100644
--- gcc/testsuite/g++.dg/cpp0x/constexpr-ctor19.C
+++ gcc/testsuite/g++.dg/cpp0x/constexpr-ctor19.C
@@ -0,0 +1,42 @@
+// PR c++/70229
+// { dg-do compile { target c++11 } }
+
+template <class>
+class S {
+  constexpr S (void) {
+    typedef int T;
+  }
+};
+
+template <class>
+class S2 {
+  constexpr S2 (void) {
+    ;
+  }
+};
+
+template <class>
+class S3 {
+  constexpr S3 (void) {
+    typedef enum { X } E;
+  } // { dg-error "does not have empty body" "" { target c++11_only } }
+};
+
+template <class>
+class S4 {
+  constexpr S4 (void) {
+    typedef struct { int j; } U;
+  } // { dg-error "does not have empty body" "" { target c++11_only } }
+};
+
+struct V
+{
+  int i;
+};
+
+template <class>
+class S5 {
+  constexpr S5 (void) {
+    typedef V W;
+  }
+};

        Marek