https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109012
Bug ID: 109012
Summary: Repeated error messages when using -std=c++23
Product: gcc
Version: 12.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: stevenxia990430 at gmail dot com
Target Milestone: ---
The following incomplete program repeatedly reports the same error message on
GCC 12 with “-std=c++23” flag.
To quickly reproduce: https://gcc.godbolt.org/z/Ehzde5o4T
```
#include <iostream>
template <class T>
myClass<myClass<myClass<myClass<myClass<T>>>>> myFunction(T item)
{
std::cout << "Hello World!";
}
```
So the C++23 parser seems to have a bug. If we remove “-std=c++23” it only
reports the concise error message once: https://gcc.godbolt.org/z/38Gxne859
Additionally, this also occurs for even syntactically invalid code snippets.
For example this code
```
myClass<myClass<myClass<myClass<myClass<int>>>>>((( myFunction(int item)
```
Also observe the same behavior, although clearly it is syntactically invalid.
This correct program compiles in less than 1 second with “g++ -c -std=c++23
correct.cpp”
```
#include <iostream>
template<typename T>
class myClass {
public:
void myFunction(const T item);
};
template <class T>
myClass<myClass<myClass<myClass<myClass<T>>>>> myFunction(T item)
{
std::cout << "Hello World!";
}
```
correct.cpp
