https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79070
Bug ID: 79070
Summary: Unhelpful error message for ambiguous type in template
parameter
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gccbugbjorn at fahller dot se
Target Milestone: ---
Compiling the below program with g++-7 on gcc.godbolt.org and other self
builts, and also older releases of g++:
namespace A {
class Foo {};
}
namespace B {
class Foo{};
}
using namespace A;
using namespace B;
template <typename T> using t = T;
using type = t<Foo>;
//Foo* p = nullptr;
gives the unhelpful error message
maggot:/tmp>g++ -std=c++14 c.cpp
c.cpp:13:19: error: template argument 1 is invalid
using type = t<Foo>;
Removing the comment for the Foo*, gives a considerably more helpful message:
maggot:/tmp>g++ -std=c++14 c.cpp
c.cpp:13:19: error: template argument 1 is invalid
using type = t<Foo>;
^
c.cpp:15:1: error: reference to 'Foo' is ambiguous
Foo* p = nullptr;
^
c.cpp:6:11: note: candidates are: class B::Foo
class Foo{};
^
c.cpp:3:11: note: class A::Foo
class Foo {};
^
