[LLVMbugs] [Bug 11764] New: decltype(MyClass()) doesn't work as a trailing return type

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sat Jan 14 06:21:47 PST 2012


             Bug #: 11764
           Summary: decltype(MyClass()) doesn't work as a trailing return
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++0x
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: jyasskin at google.com
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Given the following program:

#include <typeinfo>
#include <iostream>
#include <vector>

template<typename T>
struct array_ref {
    array_ref(const std::vector<T>& v) {}

template<typename T>
auto make_array_ref(const T& t) -> decltype(array_ref<int>(t)) {
    return array_ref<int>(t);

template<typename T>
void WriteType(T t) {
    std::cout << typeid(decltype(array_ref<int>(t))).name() << '\n';

int main() {
    std::vector<int> v;

clang++ -std=c++11 gives the following error:

test.cc:12:12: error: no viable conversion from 'array_ref<int>' to
    return array_ref<int>(t);
1 error generated.

The lack of 'aka' is bug 10405, but I believe the code should compile as-is. It
does with gcc-4.6, and the decltype() expression is exactly the same as the
returned expression. Further, when I comment out make_array_ref(), clang and
gcc print "9array_refIiE" (array_ref<int>), which is the type of the return

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