http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54311
Bug #: 54311
Summary: Info about default template arguments in instantiation
backtrace
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: zeratul...@hotmail.com
Consider the following (invalid) code:
template <typename>
class A {};
template <typename T,
typename U = typename A<T>::type>
class B {};
int main()
{
B<int> b;
}
GCC's error message is as follows:
test.cpp: In function 'int main()':
test.cpp:10:10: error: no type named 'type' in 'class A<int>'
B<int> b;
^
test.cpp:10:10: error: template argument 2 is invalid
test.cpp:10:13: error: invalid type in declaration before ';' token
B<int> b;
^
Someone looking at this backtrace might be confused as to why A<int> is being
instantiated, as the backtrace doesn't show the line that asks for this
instantiation (that line being "typename U = typename A<T>::type"). The
"template argument 2 is invalid" message provides a hint, but I don't think
it's enough.
I think the error message should be changed to the following:
test.cpp: In function 'int main()':
test.cpp:5:38: error: no type named 'type' in 'class A<int>'
typename U = typename A<T>::type>
^
test.cpp:10:10: required from here
B<int> b;
^
test.cpp:10:13: error: invalid type in declaration before ';' token
B<int> b;
^
