https://llvm.org/bugs/show_bug.cgi?id=26047
Bug ID: 26047
Summary: erroneous substitution failure through a type alias on
variadic template
Product: clang
Version: 3.6
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: C++11
Assignee: unassignedclangb...@nondot.org
Reporter: eric.s.wall...@intel.com
CC: dgre...@apple.com, llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 15571
--> https://llvm.org/bugs/attachment.cgi?id=15571&action=edit
The test case from the description, but pre-processed
The following code seems to produce an erroneous substitution failure:
====
template <typename... Ts>
struct function
{
};
template <typename... Ts>
using Callback = function<void(Ts...)>;
template <typename... Ts>
void foo(Callback<Ts...> callback)
{
}
void foo_int(Callback<int> callback)
{
}
template <typename... Ts>
void foo_no_type_indirection(function<void(Ts...)> callback)
{
}
int main()
{
Callback<int> callback = function<void(int)>{};
foo_int(callback); // succeeds
foo_no_type_indirection(callback); // succeeds
foo(callback); // fails: substitution failure
return 0;
}
====
Note that if the substitution is done by hand (the "foo_int" case), the call
succeeds. Also if we don't go through the "Callback" type alias (the
"foo_no_type_indirection" case), the call succeeds. Variadic templates are also
required here; when I tested using a single argument template, clang succeeded.
This test case compiles with gcc4.8.
There are a few other substitution failures kicking around in the bug list, but
none looked quite like this. I thought this test case might be useful even if
it turns out to be a duplicate problem.
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