[C++ PATCH] Reject trailing return type for operator auto()

[Ville Voutilainen]

Tested on Linux-x64.

/cp
2014-12-19  Ville Voutilainen  <ville.voutilai...@gmail.com>

    Reject trailing return type for an operator auto().
    * decl.c (grokdeclarator): Reject trailing return types for
    all conversion operators, don't handle conversion operators
    in the previous checks that deal with auto.

/testsuite
2014-12-19  Ville Voutilainen  <ville.voutilai...@gmail.com>

    Reject trailing return type for an operator auto().
    * g++.dg/cpp0x/auto9.C: Adjust.

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index bbaf3d6..5ff8cab 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -9775,7 +9775,7 @@ grokdeclarator (const cp_declarator *declarator,
                            virtualp = false;
                          }
                      }
-                   else if (!is_auto (type))
+                   else if (!is_auto (type) && sfk != sfk_conversion)
                      {
                        error ("%qs function with trailing return type has"
                               " %qT as its type rather than plain %<auto%>",
@@ -9783,7 +9783,8 @@ grokdeclarator (const cp_declarator *declarator,
                        return error_mark_node;
                      }
                  }
-               else if (declarator->u.function.late_return_type)
+               else if (declarator->u.function.late_return_type
+                        && sfk != sfk_conversion)
                  {
                    if (cxx_dialect < cxx11)
                      /* Not using maybe_warn_cpp0x because this should
@@ -9892,6 +9893,8 @@ grokdeclarator (const cp_declarator *declarator,
                    maybe_warn_cpp0x (CPP0X_EXPLICIT_CONVERSION);
                    explicitp = 2;
                  }
+               if (late_return_type_p)
+                 error ("a conversion function cannot have a trailing return 
type");
              }
 
            arg_types = grokparms (declarator->u.function.parameters,
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto9.C 
b/gcc/testsuite/g++.dg/cpp0x/auto9.C
index 0c0f39f..83efbaa 100644
--- a/gcc/testsuite/g++.dg/cpp0x/auto9.C
+++ b/gcc/testsuite/g++.dg/cpp0x/auto9.C
@@ -21,8 +21,8 @@ struct A
 
 struct A2
 {
-  operator auto () -> int;                     // { dg-error "invalid use of" 
"" { target { ! c++14 } } }
-  operator auto *() -> int;                    // { dg-error "auto" }
+  operator auto () -> int;                     // { dg-error "invalid use 
of|trailing return type" }
+  operator auto*() -> int;                     // { dg-error "invalid use 
of|trailing return type" }
 };
 
 template <typename> struct B