Dear Maintainer,
* What led up to the situation?
When specifying a 'using' declaration the compiler produces an error when the
-fmodules-ts flag is used.
* What exactly did you do (or not do) that was effective (or
ineffective)?
The following program compiles correctly when -fmodules is *not* specified,
and produces an error when -fmodules *is* specified. In the latter case: if
instead of the #include directives 'import' statements (like 'import
<vector>;' are used the same error results. But when '#include <iostream>' (or
'import <iostream>;' is omitted compilation using the -fmodules-ts flag
correctly completes.
The following source file (between ======= lines) was compiled by calling:
g++ --std=c++23 -Wall -fmodules-ts -freport-bug -c main.cc
===================================================
#include <iostream>
#include <vector>
int main()
{
using VectorInt = std::vector<int>;
VectorInt vi(3);
}
===================================================
* What was the outcome of this action?
main.cc: In function ‘int main()’:
main.cc:6:38: error: wrong number of template arguments (1, should be 2)
6 | using VectorInt = std::vector<int>;
| ^
In file included from /usr/include/c++/14/ostream:43,
from /usr/include/c++/14/iostream:41,
of module /usr/include/c++/14/iostream, imported at main.cc:1:
/usr/include/c++/14/format:2577:36: note: provided for ‘template<class, class> class std::vector’
2577 | template<typename, typename> class vector;
| ^~~~~~
main.cc:6:28: error: ‘<expression error>’ in namespace ‘std’ does not name a type
6 | using VectorInt = std::vector<int>;
| ^~~~~~~~~~~
main.cc:8:5: error: ‘VectorInt’ was not declared in this scope
8 | VectorInt vi(3);
| ^~~~~~~~~
* What outcome did you expect instead?
The same as when -fmodule-ts is not specified: errorless compilation