[PATCH] c++: Don't show constructor internal name in error message [PR105483]

[Simon Martin]

Hi Jason,

On 26 Aug 2024, at 19:30, Jason Merrill wrote:

> On 8/26/24 12:49 PM, Simon Martin wrote:
>> We mention 'X::__ct' instead of 'X::X' in the "names the constructor,

>> not the type" error for this invalid code:
>>
>> === cut here ===
>> struct X {};
>> void g () {
>>    X::X x;
>> }
>> === cut here ===
>>
>> The problem is that we use %<%T::%D%> to build the error message, 
>> while
>> %qE does exactly what we need since we have DECL_CONSTRUCTOR_P. This 
>> is
>> what this patch does, along with skipping until the end of the 
>> statement
>> to avoid emitting extra (useless) errors.
>>
>> Successfully tested on x86_64-pc-linux-gnu.
>>
>> 	PR c++/105483
>>
>> gcc/cp/ChangeLog:
>>
>> 	* parser.cc (cp_parser_expression_statement): Use %qE instead of
>> 	incorrect %<%T::%D%>, and skip to end of statement.
>>
>> gcc/testsuite/ChangeLog:
>>
>> 	* g++.dg/tc1/dr147.C: Adjust test expectation.
>> 	* g++.dg/diagnostic/pr105483.C: New test.
>>
>> ---
>>   gcc/cp/parser.cc                           | 7 ++++---
>>   gcc/testsuite/g++.dg/diagnostic/pr105483.C | 7 +++++++
>>   gcc/testsuite/g++.dg/tc1/dr147.C           | 2 +-
>>   3 files changed, 12 insertions(+), 4 deletions(-)
>>   create mode 100644 gcc/testsuite/g++.dg/diagnostic/pr105483.C
>>
>> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
>> index 28ebf2beb60..ef4e3838a86 100644
>> --- a/gcc/cp/parser.cc
>> +++ b/gcc/cp/parser.cc
>> @@ -13240,10 +13240,11 @@ cp_parser_expression_statement (cp_parser* 
>> parser, tree in_statement_expr)
>>   	       && DECL_CONSTRUCTOR_P (get_first_fn (statement)))
>>   	{
>>   	  /* A::A a; */
>> -	  tree fn = get_first_fn (statement);
>>   	  error_at (token->location,
>> -		    "%<%T::%D%> names the constructor, not the type",
>> -		    DECL_CONTEXT (fn), DECL_NAME (fn));
>> +		    "%qE names the constructor, not the type",
>> +		    get_first_fn (statement));
>> +	  cp_parser_skip_to_end_of_block_or_statement (parser);
>
> Why block_or_statement rather than just _statement?
It was a mistake, thanks for catching it!

> Maybe move the skip+return out of this block to share it with the 
> preceding typename error?
Good idea. It’s a tiny bit more involved than just moving, because 
we’d miss genuine errors emitted by 
cp_parser_consume_semicolon_at_end_of_statement (e.g. break the 
c-c++-common/pr44515.c test, among others), however the updated patch 

does what you’re suggesting. I have successfully tested on 
x86_64-pc-linux-gnu. OK for trunk?

Thanks!
   Simon
>
> Jason
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