Re: PING: C++0x decltype patch

[Nathan Sidwell <nathan at codesourcery dot com>]

Doug,
> The first sorry(), for BIT_FIELD_REF, should be a gcc_unreachable; it
> just can't happen here. The second "sorry" I'd like to keep... if we
> get here, it means that I somehow missed a particular member-access
> expression node. So, apologize to the user and when they report the
> bug, we'll see what the expression code is to fix the bug. Perhaps
> internal_error would be better?

IMHO that's exactly what
	gcc_assert (TYPE_P (expr) || DECL_P (expr))
is for :)  sorry is for pieces we _know_ we've not implemented.  Here we _think_ 
we've covered all the cases, so an assert is appropriate.

> > here you parse tentatively, but don't appear to be committing to the tentative
> > parse when it succeeds.
>
> Ah, thanks. The fix is:
>
>   if (id_expression_or_member_access_p)
>     /* We have parsed the complete id-expression or member access.  */
>     cp_parser_parse_definitely (parser);
>   else
>     {
>       /* Abort our attempt to parse an id-expression or member access
>          expression.  */
>       cp_parser_abort_tentative_parse (parser);
>
>       /* Parse a full expression.  */
>       expr = cp_parser_expression (parser, /*cast_p=*/false);
>     }
>
> Essentially, by the time we reach this spot, we've either parsed an
> id-expression or class member access expression, in which case there
> is nothing left to tentatively parse (so we commit); or, we need to
> abort the previous attempts and parse a full expression.

Yup.

> > Also, I can't see where decltype is gated on using c++0x extensions
>
> In lex.c, if the keyword is only available when in C++0x mode, then
> the feature is only available in C++0x mode:
>
>   { "decltype",         RID_DECLTYPE,   D_CXX0X },
>
> That said, decltype can save us (and the compiler) a LOT of work in
> libstdc++, so I would suggest also:
>
>   { "__decltype",       RID_DECLTYPE,   0 },

I'm fine with this.

> Updated patch attached, with those changes/fixes mention above.
> Regtested powerpc-apple-darwin8.10.0, no regressions. Okay?

I would still like the other sorry turned into gcc_assert, for the reasons I 
mentioned.

nathan
--
Nathan Sidwell    ::   http://www.codesourcery.com   ::         CodeSourcery
nathan@codesourcery.com    ::     http://www.planetfall.pwp.blueyonder.co.uk