Re: C++ PATCH for c++/89511 - ICE with using-declarations and unscoped enumerator

[Marek Polacek]

On Wed, Feb 27, 2019 at 10:53:16AM -0500, Jason Merrill wrote:
> On 2/26/19 5:13 PM, Marek Polacek wrote:
> > Here we ICE because the unscoped enum's context is a FUNCTION_DECL, which
> > push_using_decl can't handle.
> > 
> > http://www.open-std.org/JTC1/SC22/WG21/docs/cwg_active.html#1742
> > says this is well-formed (but the scoped enum case is ill-formed).
> > Nevertheless, the DR hasn't been resolved either way yet, and trying
> > to accept a FUNCTION_DECL as a USING_DECL_SCOPE seems like a lot of
> > work, and ultimately maybe both cases will be deemed ill-formed.
> > 
> > This patch fixes the ICE by giving the pre-r211479 error while
> > simultaneously keeping using-enum-[12].C working.
> > 
> > Bootstrapped/regtested on x86_64-linux, ok for trunk?
> > 
> > 2019-02-26  Marek Polacek  <pola...@redhat.com>
> > 
> >     PR c++/89511 - ICE with using-declarations and unscoped enumerator.
> >     * parser.c (cp_parser_using_declaration): For an unscoped enum
> >     only use its context if it's a namespace declaration.
> > 
> >     * g++.dg/cpp0x/using-enum-3.C: New test.
> > 
> > diff --git gcc/cp/parser.c gcc/cp/parser.c
> > index e976008e94d..361dc9d065e 100644
> > --- gcc/cp/parser.c
> > +++ gcc/cp/parser.c
> > @@ -19412,7 +19412,8 @@ cp_parser_using_declaration (cp_parser* parser,
> >                                               /*is_declaration=*/true);
> >     if (!qscope)
> >       qscope = global_namespace;
> > -  else if (UNSCOPED_ENUM_P (qscope))
> > +  else if (UNSCOPED_ENUM_P (qscope)
> > +      && TREE_CODE (CP_TYPE_CONTEXT (qscope)) == NAMESPACE_DECL)
> >       qscope = CP_TYPE_CONTEXT (qscope);
> 
> Hmm, surely we want to handle class scope enums here, too?  Maybe
> !TYPE_FUNCTION_SCOPE_P instead.

I guess so.  It doesn't really make a huge difference, because
do_class_using_decl will call error_not_base_type in either case, but it
changes the error message from 
error: type ‘S’ is not a base type for type ‘S’
to
error: type ‘S::E’ is not a base type for type ‘S’
and I think we want to keep the former.  Thus updated patch, with more
testing:

Bootstrap/regtest running on x86_64-linux, ok for trunk if it passes?

2019-02-27  Marek Polacek  <pola...@redhat.com>

        PR c++/89511 - ICE with using-declaration and unscoped enumerator.
        * parser.c (cp_parser_using_declaration): For an unscoped enum
        only use its context if it's not a function declaration.

        * g++.dg/cpp0x/using-enum-3.C: New test.

diff --git gcc/cp/parser.c gcc/cp/parser.c
index d9824e40803..5f694033496 100644
--- gcc/cp/parser.c
+++ gcc/cp/parser.c
@@ -19412,7 +19412,8 @@ cp_parser_using_declaration (cp_parser* parser,
                                                  /*is_declaration=*/true);
   if (!qscope)
     qscope = global_namespace;
-  else if (UNSCOPED_ENUM_P (qscope))
+  else if (UNSCOPED_ENUM_P (qscope)
+          && !TYPE_FUNCTION_SCOPE_P (qscope))
     qscope = CP_TYPE_CONTEXT (qscope);
 
   if (access_declaration_p && cp_parser_error_occurred (parser))
diff --git gcc/testsuite/g++.dg/cpp0x/using-enum-3.C 
gcc/testsuite/g++.dg/cpp0x/using-enum-3.C
new file mode 100644
index 00000000000..edc16890cb1
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp0x/using-enum-3.C
@@ -0,0 +1,21 @@
+// PR c++/89511
+// { dg-do compile { target c++11 } }
+
+void f ()
+{
+  enum e { a };
+  using e::a; // { dg-error "not a namespace or unscoped enum" }
+}
+
+struct S {
+  enum E { A };
+  using E::A; // { dg-error "type .S. is not a base type for type .S." }
+};
+
+namespace N {
+  enum E { B };
+}
+
+struct T {
+  using N::E::B; // { dg-error "using-declaration for non-member at class 
scope" }
+};