http://llvm.org/bugs/show_bug.cgi?id=15757
Bug ID: 15757
Summary: Mysterious error with inheriting constructor,
delegating constructor, and noexcept specifier
Product: clang
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: C++11
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
This is as far as I've been able to narrow this problem down. It seems to be
some strange confluence of C++11 features that is causing the perfect storm:
{{{
struct S
{};
template<typename X, typename Y>
struct T
{
template<typename A>
T(X x, A &&a)
{}
template<typename A>
explicit T(A &&a)
noexcept(noexcept(
T(X(), static_cast<A &&>(a))
))
: T(X(), static_cast<A &&>(a))
{}
};
template<typename X, typename Y>
struct U
: T<X, Y>
{
using T<X, Y>::T;
};
// Comment this function out and everything works
U<S, char> foo(char ch)
{
return U<S, char>(ch);
}
int main()
{
U<S, int> a(42); // This works
U<S, char> b('4'); // This fails
}
}}}
The error I'm getting is:
1> "C:/cygwin/usr/local/bin/clang++.exe" -c -O0 -std=gnu++11 main.cpp -o
main.o
1> main.cpp:14:20: error: cannot cast from lvalue of type 'char' to rvalue
reference type 'S &&'; types are not compatible
1> T(X(), static_cast<A &&>(a))
1> ^~~~~~~~~~~~~~~~~~~~
1> main.cpp:24:20: note: in instantiation of exception specification for
'T<char>' requested here
1> using T<X, Y>::T;
1> ^
1> main.cpp:36:16: note: inheriting constructor for 'U<S, char>' first
required here
1> U<S, char> b('4'); // This fails
1> ^
1> 1 error generated.
I can't make any sense of the error message. Seemingly innocuous changes to the
code, like commenting out the foo function or the noexcept clause, make the
error go away.
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