[LLVMbugs] [Bug 23689] New: Initializer list alias cannot be used in template type inferring scenarios

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=23689

            Bug ID: 23689
           Summary: Initializer list alias cannot be used in template type
                    inferring scenarios
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++11
          Assignee: unassignedclangbugs at nondot.org
          Reporter: daniel at octaforge.org
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Clang doesn't like when I alias std::initializer_list (using template type
alias) and use that in a function that infers its inner type. Here's an
example:

==========
#include <stdio.h>
#include <initializer_list>

template<typename T>
using IList = std::initializer_list<T>;

template<typename T>
T foo(IList<T> x) {
    return *x.begin();
}

int main() {
    printf("%d\n", foo({ 5, 10, 15 }));
    return 0;
}
========

This wil fail with:

========
ilist.cpp:13:20: error: no matching function for call to 'foo'
    printf("%d\n", foo({ 5, 10, 15 }));
                   ^~~
ilist.cpp:8:3: note: candidate template ignored: couldn't infer template
argument 'T'
T foo(IList<T> x) {
  ^
1 error generated.
========

Changing it to initializer_list (i.e. not using the alias) works. When the
template type is explicitly specified, it also works (thus it's not a problem
for example in class constructors).

Regards,

Daniel

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