[llvm-bugs] [Bug 44952] New: Clang doesn't accept default arguments followed by parameter pack

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=44952

            Bug ID: 44952
           Summary: Clang doesn't accept default arguments followed by
                    parameter pack
           Product: clang
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: aaronpuchert at alice-dsl.net
                CC: llvm-bugs at lists.llvm.org, neeilans at live.com,
                    richard-llvm at metafoo.co.uk

Clang emits an error for the following code:

template<typename... Args>
int f(int a = 5, Args... args);

int main() {
  return f(1, 2, 3);
}

<source>:2:26: error: missing default argument on parameter 'args'
int f(int a = 5, Args... args);
                         ^
<source>:5:10: note: in instantiation of function template specialization
'f<int, int>' requested here
  return f(1, 2, 3);
         ^

But [dcl.fct.default]p4 says "In a given function declaration, each parameter
subsequent to a parameter with a default argument shall have a default argument
supplied in this or a previous declaration, unless the parameter was expanded
from a parameter pack, or shall be a function parameter pack."

So unless I'm missing something, this should be allowed.

(Reported by pftbest on IRC.)

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