Re: [patch] fix PR c++/14136: Duplicate error message (take two)

[Mark Mitchell <mark at codesourcery dot com>]

Volker Reichelt wrote:
> On 15 Dec, Mark Mitchell wrote:
>
> > Volker Reichelt wrote:
> >
> > > Ok, here's take two.
> > >
> > > For the following code snippet we issue a duplicate diagnostic on mainline:
> > >
> > > ==========================
> > > struct A
> > > {
> > >    typedef A B;
> > >    ~B();
> > > };
> > > ==========================
> > >
> > > PR14136.cc:4: error: typedef-name 'A::B' used as destructor declarator
> > > PR14136.cc:4: error: typedef-name 'A::B' used as destructor declarator
> > >
> > > This is because in cp_parser_member_declaration we first call
> > > cp_parser_parse_and_diagnose_invalid_type_name. This eventually ends
> > > up in calls cp_parser_unqualified_id which issues the first error message.
> > > (Btw, the duplicate error message first appeared when
> > > cp_parser_parse_and_diagnose_invalid_type_name was introduced.)
> > >
> > > Later in cp_parser_member_declaration we call cp_parser_declarator.
> > > This again ends up in cp_parser_unqualified_id so that the second
> > > error message is issued.
> > >
> > > The following patch suppresses the first error message which was
> > > issued in an uncommitted tentative parse.
> >
> > Doesn't it make more sense to avoid cp_parser-diagnose_invalid_type_name 
> > in a tentative parse?  If not, it probably makes sense to commit to the 
> > tentative parse at that point.  The c_p_d_i_t function is only used to 
> > issue diagnostics, it seems like nothing more than a waste of time to be 
> > using it during tentative parsing.
>
>
> We are not calling c_p_d_i_t inside a tentative parse. Instead c_p_d_i_t
> starts a tentative parse to see whether two identifiers follow or not.
> If not (i.e. no error is detected), the tentative parse is aborted.

Thanks for the explanation; the patch is OK.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
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